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A Randomized Trial of Nurse Intervention to Reduce Preterm and Low Birth Weight Births 1
A Randomized Trial of Nurse Intervention to Reduce Preterm and Low Birth Weight Births MARY LOU MOORE, PhD, RNC, PAUL J. MEIS, MD, J. M. ERNEST, MD, H. BRADLEY WELLS, PhD, DANIEL J. ZACCARO, MS, AND TIM TERRELL, MS Objective: To test the effect of telephone calls from registered nurses to low-income pregnant women on the rates of low birth weight (LBW) and preterm births. Methods: A total of 1554 women receiving prenatal care in a public clinic who met study criteria and who consented were assigned randomly to intervention and control groups. Women in the intervention group received telephone calls from a registered nurse, one or two times weekly from 24 weeks’ through 37 weeks’ gestation. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated. Results: Low birth weight rates were 10.9% in the intervention group and 14.0% in the control group (RR 0.75; 95% CI 0.55, 1.03; P 5 .072). For gestational age less than 37 weeks, rates were 9.7 in the intervention group and 11.0 in the control group (RR .87; 95% CI 0.62, 1.22; P 5 .415). In the subgroup of low-income black women 19 years of age and older, a statistically significant difference was found in preterm birth rates before 37 weeks (8.7% in the intervention group versus 15.4% in the controls [RR 0.56; 95% CI 0.38, 0.84; P 5 .004]). Conclusion: There was no difference in LBW or preterm births between intervention and control groups in the total sample. In a secondary analysis of black subjects 19 years of age and older, there was a significant difference in preterm birth rates. (Obstet Gynecol 1998;91:656 – 61. © 1998 by The American College of Obstetricians and Gynecologists.)
Low birth weight (LBW) and preterm births remain the major factors in infant mortality and morbidity in the United States. Consistently, rates of LBW and preterm births have been highest in black women and in adolescents.1,2 High rates of infant mortality among black infants reflect higher rates of LBW births. Although both black and white mortality rates decreased between 1990 and 1992, in 1992, the black-white ratio for neonaFrom the Departments of Obstetrics and Gynecology and Public Health Sciences, Wake Forest University School of Medicine, WinstonSalem, North Carolina. Supported by Grant NRO2410-01, National Institute of Nursing Research, National Institutes of Health.
656 0029-7844/98/$19.00 PII S0029-7844(98)00012-X
tal mortality, based on maternal race, was 2.5, an increase from a ratio of 2.4 in 1990. The ratio for postneonatal mortality remained at 2.3.3 In 1994, there was a LBW rate of 13.2% and a preterm delivery rate of 18.4% among blacks.4 Programs to reduce the incidence of preterm and/or LBW births that focus on risk assessment, client and provider education, and more frequent prenatal contacts showed promising results in populations of middle-class women5,6 and rural women,7,8 but these results were not replicated in subsequent randomized trials. Most randomized controlled trials in low-income populations in the United States, Europe, and Latin America have failed to demonstrate differences between intervention and control groups.9 –18 Home visits by midwives or registered nurses were the primary intervention in studies by Blonde et al14 in Paris, Villar et al15 in Latin America, and Olds et al10 in the United States. In the United Kingdom, home visits by a “family worker” who was a laywoman provided social support to reduce the level of stress.12 In each of these studies,10,12,14,15 the target population was a group of women identified as “high-risk” by relatively similar criteria. Telephones have been used by health care providers in the United States in a variety of ways to provide health information and health care. Telephone counseling from a nurse who provides advice and support has been an important part of some programs of preterm birth prevention in which home uterine activity monitoring has been used.19,20 One study21 suggests that the nursing telephone contact per se may be as effective in reducing LBW as home uterine activity monitoring. However, in a small randomized trial of women with a previous preterm birth, no difference was found between subjects who received daily telephone calls and control subjects.22 The importance of a nurturing relationship between a nurse and a pregnant woman in the outcome of preg-
Obstetrics & Gynecology
nancy has been suggested.5,9 In the model described by Herron and associates,5 a key feature was the close relationship of the project nurse with subjects. Olds et al10 found that young adolescents who were visited at home by nurses gave birth to infants who weighed an average of 395 g more (P 5 .02) than those who did not receive home visits. The hypothesis we tested was that low-income women who receive a single personal visit and telephone calls from a registered nurse between 24 and 37 weeks’ gestation will have a lower incidence of LBW and preterm births than women who do not receive calls.
Materials and Methods This study was a randomized trial and was approved by the Clinical Research Practice Committee of the Bowman Gray School of Medicine. Three groups of women in the community public clinic were included in the sample, based on low birth weight rates from the 2 years before initiation of the study. They were black women (all ages), white and “other” women with a preterm labor risk score of at least 7 on the Wake Forest University School of Medicine risk assessment tool,22,23 and white or “other” women 18 years of age or younger. All potential subjects spoke English. In addition, potential subjects needed access to a telephone, although not necessarily in their own home. Subjects were entered into the study between 22 and 32 weeks’ gestation. Random assignment was directed by the biostatistician. The words “phone” for the intervention group and “book” for the control group were placed in opaque envelopes that were numbered and sealed by the biostatistician, following a computer randomization table. Each nurse carried a box of sequentially numbered envelopes with her. Eligible women were identified weekly on an original list from the clinic records. Risk assessment was conducted as a part of normal clinic protocol. Contact was made by letter and followed by a telephone call to make an appointment for a personal visit from a nurse hired specifically for this study. If the woman did not have a telephone, efforts were made to contact her through family members or by leaving a note on her door. During the personal visit, the project was explained, and the woman was asked to sign a consent form. After consenting, each woman was interviewed to collect baseline data (health history and psychosocial assessment) and assigned to intervention or control groups by choosing the next sealed opaque envelope from a box prepared previously by the biostatistician. The interview with women in the control group concluded with information about a questionnaire they
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would receive in the mail at 34 weeks’ gestation and a $10 gift certificate they would receive if they returned the questionnaire. They also were given a booklet about preventing preterm labor; the same booklet was available in the clinic. Women in the intervention group received additional instruction about the signs of preterm labor, and a schedule was established for the time and frequency of telephone calls they would receive from the nurse, as well as instructions about contacting the nurse by telephoning her pager number. They were told about the 34-week questionnaire and that they would receive a $25 gift certificate at 37 weeks or after the birth of their baby, if they returned their assessment and remained in contact with the nurse by telephone. A tracking sheet was completed for every woman registered in the clinic list. Women were identified as eligible, accessible by telephone or not, agreeing to the personal visit for enrollment, participating in the enrollment visit, and randomized to the intervention or control group. A woman was dropped from the study if she moved from the community or if she transferred to another prenatal care provider. Nurse telephone calls were made on the schedule to which nurse and subject agreed, from the time of the home visit (22–32 weeks’ gestation) until the 37th week. The timing of the calls was designed to suit the woman’s convenience. The goal was three telephone contacts per week. Women without telephones could contact their primary nurse via the nurse’s pager when they were near a telephone. The nurse returned the call immediately. Although no formal script was followed, each telephone call addressed three major areas: assessment of health status (perception of uterine contractions and other pregnancy changes, color of urine as an assessment of hydration, number of meals eaten, number of cigarettes smoked, alcohol and drug use, and ingestion of a prenatal vitamin capsule on the previous day); recommendations based on assessment; and discussion of any additional issues important to the mother. The duration of each call was recorded. Three experienced nurses, hired specifically for the telephone intervention study, conducted the intake interviews and all of the telephone intervention. All of the nurses were white. These nurses did not attend clinic, nor did they have any further contact with subjects other than telephone calls after the initial home visit. Clinic personnel, including attending physicians, residents, nurses, and others were blinded to group assignment. If a referral to clinic, the labor suite, or another agency was needed, the nurse instructed the patient to make the call and then ascertained that the call was made. Data collection was done by an additional nurse hired specifically for this task. She did not participate in
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the intervention, was not present at any meetings during which patients were discussed, and was blinded to group assignment. Data were collected through interview at the personal visit and from the 34-week mailed assessment, prenatal records at the clinic and intrapartum and neonatal records at the hospital by a data collection nurse, and the logs kept by the intervention nurses. All data were collected on paper forms that were entered by trained data entry staff into a relational database system, which enforced range and data type restrictions. Data quality analysis was achieved with data quality check reporting, data audits, double-entry, and inter-rater reliability checks. The estimated date of confinement was calculated by the best available criteria: date of last menstrual period (LMP) when known, uterine size as determined at initial prenatal examination, and ultrasound measurements when indicated. Criteria for ultrasound measurements included unknown or uncertain LMP, an LMP that did not correlate with uterine size, and late entry into prenatal care. Antecedent variables in the intervention and control groups were compared by x2 test for categoric variables and two sample t tests for continuous variables. The primary outcomes of interest and difference in the rates of LBW infants and of births before 37 weeks were tested by calculating relative risks (RRs) and 95% confidence intervals (CIs). Comparisons were made between the control and intervention groups stratified by ethnicity (black versus white or other) and by age grouping (18 or younger versus 18) within ethnicity strata. With two outcome variables of interest (low birth weight status and premature status), this made eight comparisons. To account for multiple hypothesis tests, an appropriate correction was made to the nominal level of statistical significance (0.05/8 5 0.006). Only those comparisons with P values smaller than this were considered statistically significant. The target sample size was projected initially for a one-sided test. To achieve 80% power a 5 .05, a sample size of 1540 was required. In the final analysis, the more conservative two-sided test was used. Analysis was on an intentionto-treat basis.
Results Of the 3127 women eligible to participate by race and risk status, we were able to contact 1850 (59.2%). The principal reasons for inability to contact were lack of phone and/or lack of permanent address. Of the contacted women, 155 (8.38%) refused participation. Women contacted after 32 weeks because of late registration for prenatal care were not randomized. Only five women (0.03%) who consented to a home visit
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Table 1. Tracking Data
Enrolled in clinic Not eligible† Eligible Eligible not included‡ Randomized Intervention Control Dropped from final analysis§ Intervention Control Available for analysis Intervention Control Total
Black
White or other*
Total
2595 291 2304 1109
2635 1812 823 464
5230 2103 3127 1573
597 598
178 181
775 779
40 42
17 22
57 64
557 556 1113
161 159 320
718 715 1433
* Other represented 6.3% of clinic population, 0.8 of study sample. The majority of other (81.9%) were not eligible because they did not speak English. † Women were not eligible if they could not be contacted before 32 weeks’ gestation; were white, low risk, and older than 18 years; or did not speak English. ‡ Women were eligible by race and age but not included if they refused or could not be contacted before 32 weeks; the majority lacked a telephone. § Women were dropped from final analysis if they had a multiple gestation, moved out of town, or transferred to a private prenatal care provider.
refused to participate after the study was explained. Of the 1850 women contacted, 1554 (84%) agreed to participate and were randomized (Table 1). One hundred twenty-one randomized women (7.8%) changed health care providers, moved from the community, or had multiple gestation pregnancies, leaving 1433 subjects for the analysis of singleton birth outcomes. No significant differences were found between the randomized groups in age, single marital status, educational level, number of pregnancies, Medicaid eligibility, preterm labor risk score, previous LBW birth, smoking, use of illicit drugs or alcohol during pregnancy, physical abuse during the current pregnancy, job requiring heavy physical work, self-reported constant or frequent high-stress state anxiety, interconceptional period less than a year, maternal age at entry into the study, total number of prenatal care visits, or weight gain during pregnancy. For white and other women only, there was a difference in physical abuse before pregnancy (32.5% in the intervention group versus 44% in the control group, P 5 .031), presumably on the basis of chance. Subgroup analyses by race (black versus white or other) and age (18 or younger versus 19 or older) were conducted for several variables. The mean gestational age at entry into the study ranged from 25.8 weeks for white subjects 18 years of age or younger to 26.7 weeks for black subjects 18 years of age or younger. There was
Obstetrics & Gynecology
Table 2. Birth Weight and Gestational Age by Race and Age of Mother
Black women Weight ,2500 g Age #18 y (n 5 353) Age $19 y (n 5 759) Gestational age ,37 wk Age #18 y (n 5 353) Age $19 y (n 5 759) White or other women Weight ,2500 g Age #18 y (n 5 213) Age $19 y (n 5 107)‡ Gestational age ,37 wk Age #18 y (n 5 213) Age $19 y (n 5 107)‡
Intervention* %
Control† %
RR
95% CI
P
11.3 11.0 11.4 9.4 11.0 8.7
15.3 11.6 17.3 12.8 7.9 15.4
.75 .95 .66 .73 1.39 .56
0.55, 1.00 0.53, 1.72 0.46, 0.94 0.52, 1.02 0.72, 2.67 0.38, 0.84
.047 .874 .020 .064 .039 .004
9.9 7.0 17.4 11.2 7.8 19.6
10.0 6.1 14.8 5.0 4.1 6.6
0.99 1.14 1.18 2.37 1.92 2.99
0.48, 2.05 0.41, 3.16 0.49, 2.82 1.00, 5.62 0.61, 6.02 0.98, 9.09
.879 .807 .712 .044 .255 .041
RR 5 relative risk; CI 5 confidence interval. * The intervention group comprised 557 black women and 161 white women. † The control group comprised 556 black women and 159 white women. ‡ The white-other sample of women $19 years of age includes only women identified as at higher risk for preterm birth; all black women were eligible for inclusion.
no difference between intervention and control groups in age of entry into the study for any subgroup nor was there a difference for any subgroup in the number of pregnancies, births, and abortions. There was no significant difference in subgroups in the median number of calls to each woman (21 to black women 18 years of age or younger and white women in either age group, and 25 to black women 19 years of age and older; P 5 .193). The median number of minutes per call was 3.6 minutes for black women 18 years of age or younger, 3.4 minutes for black women 19 years of age or older, 3.2 minutes for white women 18 years of age or younger, and 3.7 minutes for white women 19 years of age or older (P 5 .802). For the total sample, LBW rates were 10.9% in the intervention group and 14.0% in controls (RR .75; 95% CI, 0.55, 1.03; P 5 .072). For gestational age less than 37 weeks, rates were 9.7 in the intervention group and 11.0 in the controls (RR .87; 95% CI, 0.62, 1.22; P 5 .415). However, among black women, there was a 26% difference in LBW rates between the intervention (11.3%) and control (15.3%) groups (RR .75; 95% CI 0.55, 1.00; P 5 .048) (Table 2). This difference came almost entirely from the subgroup of black women 19 years of age and older; in this subgroup, there was a 34% difference between the intervention and control groups (11.4% and 17.3%; RR .66; 95% CI 0.46, 0.94; P 5 .020). Similarly, a 27% decrease in births at gestational ages before 37 weeks was found among black women in the intervention group (9.4%) compared with those in the control group (12.8%) (RR .73; 95% CI 0.52, 1.02; P 5 .066). Among women 19 years of age and older, the differences in LBW birth were 34% (11.4% versus 17.3%; RR
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.66; 95% CI 0.46, 0.94; P 5 .02). For preterm birth, the difference was 44% (8.7% versus 15.4%; RR .56; 95% CI 0.38, 0.84; P 5 .004). We were concerned about the higher rates of preterm birth in the subgroup of white women 19 years of age or older in the intervention group (19.6%) compared with those in the control group (6.6%). In subgroup analyses, there were no differences in the intervention and control groups, except for cigarette smoking. In the intervention group, 41 of 47 (87.2%) were smokers compared with 46 of 65 (70.8%) in the control group (P 5 .039). Moreover, 75% of the intervention group smoked more than ten cigarettes each day compared with 61% of the control group. When we examined the smokingintervention interaction effect, the odds ratio (OR) for LBW births was 40% lower for nonsmokers than for smokers (P 5 .12). For birth before 37 weeks, the OR was 53% lower (P 5 .04). We examined differences in both LBW and preterm births outcome among high- and low-risk women of both racial and age groups. No statistically significant difference existed except for preterm birth among lowrisk black women older than 19 years old (5.7% for intervention versus 11.51% for control; P 5 .027).
Discussion The findings in this study are inconclusive as to the benefits of telephone intervention. For the total sample, there was no difference between intervention and control groups. However, the intervention was effective in the largest subgroup (black women 19 years and older) but not in black teens or white women. There are
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several possible reasons. First, the black and whiteother groups were not similar. In the group of black women, the whole population was eligible, rather than a high-risk subset of the population. All black women receiving care at the target clinic were eligible for inclusion; among women of white or other raceethnicity, only those who were identified as high-risk on the risk assessment form or were 18 years of age and younger were included. Second, LBW and preterm birth rates have been higher historically in black and white-other populations, with the difference increasing in recent years. Higher rates of preterm birth in white women 19 years and older in the intervention group were of particular concern. The only variable that was associated with this high rate of prematurity was cigarette smoking. Although cigarette smoking was a focus of the telephone intervention, and there was a reduction in smoking, the intervention did not begin until 24 weeks (median 26 weeks), and the reduction or cessation in smoking came in the third trimester. That 87% of women in this subgroup were still smoking, with 75% smoking more than ten cigarettes a day at the time of enrollment late in the second trimester, suggests that intervention directed at smoking cessation during prenatal visits had minimal effects. The lack of difference in young black women, 18 years of age and younger, was not due to increased rates in the intervention group but to rates in the control group comparable to the intervention groups in both age groupings. Rates among black women in the intervention group were virtually identical for both age groups (11.0 for ages up to 18 and 11.4 for ages 19 and older), but rates in the control groups were markedly different (11.6 for ages up to 18 and 17.3 for ages 19 and older). Rates were lower for teens of white or other race-ethnicity (7.0 in the intervention group and 6.1 in the control group) than black teens, but there was no significant difference between the intervention and control groups. Strong community support for pregnant teens, including an optional high school program with daily classes by a nurse focusing on pregnancy and parenting, may have provided the extra education and support to teens in the control group. In contrast, black women 19 years of age and older, lacking that support, appeared to benefit most from the extra education and support of the telephone intervention. When we examined the data by risk status, we found that most of our reduction in LBW was in women who were identified at low risk on the preterm labor risk assessment. It would be interesting to test the effects of this program in low-risk white women. For a number of years, the main focus of many preterm labor programs has been on women identified as high risk on various
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but similar risk assessment instruments. One of the frustrations with risk assessment has been the failure to identify approximately 50% of women who deliver preterm and/or LBW infants. A population-based program with increased attention to women without traditional risk factors in the black community may be one strategy to address high rates of LBW births in this population. This study raises at least four questions. First, would more frequent calls have enhanced the results? Although our goal was three calls per week, and three calls were attempted, only half of the calls, approximately 1.5 per week (21.7 over 14 weeks) were completed. The mean is only slightly affected by those women delivering earlier because of the small numbers in those groups. The mean number of minutes per patient for women who delivered between 31 and 36 weeks was 75.2 compared with 74.3 for women delivering after 37 weeks. Second, would telephone intervention be equally successful in a broader population that includes women with increased income and educational levels? Yawn and Yawn7 made a major impact on this population through office-based education. Third, what effect would the intervention have had on low-income women of white or other race-ethnicity 19 years of age and older who did not have medical risk factors? These women were not included in the original design, because their rates of LBW and preterm birth were lower than those of other population subgroups in the target clinic. In the sample of black women for this study, which was based in the total clinic population, there was a significant decrease in preterm birth between low-risk women in the intervention and control groups. Although rates of LBW and preterm birth are lower in women of white or other race-ethnicity than in black women, even a small reduction would be worthwhile. Fourth, how would a telephone intervention compare with a program of home visiting? Telephone intervention is clearly more cost effective. We estimated the cost of 14 weeks of telephone intervention to be similar to the cost of a single home visit when travel costs and time as well as visit time were included. Certain activities (blood pressure evaluation, for example) usually require home visiting. Studies designed to answer these questions may improve our ability to reduce preterm and LBW birth.
References 1. Collins JW, David RJ. The differential effect of traditional risk factors on infant birthweight among blacks and whites in Chicago. Am J Public Health 1990;80:678 – 81.
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2. Schoendorf KC, Hogue C, Kleinman J, Rowery D. Mortality among infants of black as compared with white college-educated parents. N Engl J Med 1992;26:1522– 6. 3. Guyer B, Strabino D, Ventura S, Singh G. Annual summary of vital statistics—1994. Pediatrics 1994;96:1029 –39. 4. Ventura S, Martin J, Toffel S, Matthews T, Clarke S. Advance report of final mortality statistics, 1992. Monthly Vital Statistics Report; vol. 43, no. 5. Hyattsville, Maryland: Public Health Service, 1994: 1– 87. 5. Herron M, Katz V, Creasy R. Evaluation of a preterm birth prevention program: A preliminary report. Obstet Gynecol 1982; 59:452–5. 6. Fangman JJ, Mark PM, Pratt L, Conway KK, Healey ML, Oswald JW, et al. Prematurity prevention programs: An analysis of successes and failures. Am J Obstet Gynecol 1994;170:744 –50. 7. Yawn BP, Yawn RA. Preterm birth prevention in a rural practice. JAMA 1989;262:230 –3. 8. Moore ML, Buescher P, Meis P, Michielutte R, Ernest JM, Sharp P. The effect of a preterm prevention program in 17 rural and 3 urban counties in northwest North Carolina. J Rural Health 1989;5:361– 70. 9. Main D, Gabbe S, Richardson D. Can preterm births be prevented? Am J Obstet Gynecol 1985;151:892– 8. 10. Olds D, Henderson C, Tatelbaum R, Chamberlin R. Improving the delivery of prenatal care and outcomes of pregnancy: A randomized trial of nurse home visitation. Pediatrics 1986;77:16 –28. 11. Mueller-Heubach E, Reddick D, Barrett B, Bente R. Preterm birth prevention: Evaluation of a prospective controlled randomized trial. Am J Obstet Gynecol 1989;160:1172– 8. 12. Spencer B, Thomas H, Morris J. A randomized controlled trial of the provision of a social support service during pregnancy; the South Manchester Family Worker Project. Br J Obstet Gynaecol 1989;96:281– 8. 13. Goldenberg R, Davis R, Copper R, Carbiss D, Andrews J, Carpenter A. The Alabama preterm birth prevention project. Obstet Gynecol 1990;75:933–9. 14. Blondel B, Breart G, Glado J, Chartier M. Evaluation of the home-visiting system for women with threatened preterm labor: Results of a randomized controlled trial. Eur J Obstet Gynecol Reprod Med 1990;34:47–58. 15. Villar J, Farnot U, Barros F, Victora C, Langer A, Belezan J. A randomized trial of psychosocial support during high-risk pregnancies. N Engl J Med 1992;327:1266 –71.
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16. Collaborative Group on Preterm Birth Prevention. Multicenter randomized, controlled trial of a preterm birth prevention program. Am J Obstet Gynecol 1993;169:352– 66. 17. Hobel C, Ross M, Bomis R, Bragonier JR, Nessim S, Sandhu M, et al. The West Los Angeles preterm birth prevention project. Am J Obstet Gynecol 1994;170:54 – 62. 18. Collaborative Group on Preterm Birth Prevention. Multicenter randomized, controlled trial of a preterm birth prevention program. Am J Obstet Gynecol 1993;169:352– 66. 19. Katz V, Gill PJ, Newman RB. Assessment of uterine activity in ambulatory patients at high risk of preterm labor and delivery. Am J Obstet Gynecol 1986;154:44 –7. 20. Morrison J, Martin JN, Martin RW, Gookin KS, Wiser WL. Prevention of preterm birth by ambulatory assessment of uterine activity: A randomized study. Am J Obstet Gynecol 1987;156:536 – 43. 21. Iams JD, Johnson F, O’Shaughnessy RW. A prospective randomized trial of home uterine activity monitoring in pregnancies at increased risk of preterm labor. Am J Obstet Gynecol 1988;159:595– 603. 22. Ernest JM, Michielutte R, Meis P, Moore ML, Sharp P. Identification of women at high risk for preterm low birthweight births. Prev Med 1988;17:60 –72. 23. Michielutte R, Ernest JM, Moore ML, Meis P, Sharp P, Wells HB, et al. A comparison of risk assessment models for term and preterm low birthweight. Prev Med 1992;21:98 –103.
Address reprint requests to:
Mary Lou Moore, PhD, RNC Department of Obstetrics and Gynecology Wake Forest University School of Medicine Winston-Salem, NC 27157-1066 E-mail: [email protected]
Received September 15, 1997. Received in revised form December 9, 1997. Accepted January 8, 1998. Copyright © 1998 by The American College of Obstetricians and Gynecologists. Published by Elsevier Science Inc.
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Low birth weight (LBW) and preterm births remain the major factors in infant mortality and morbidity in the United States. Consistently, rates of LBW and preterm births have been highest in black women and in adolescents.1,2 High rates of infant mortality among black infants reflect higher rates of LBW births. Although both black and white mortality rates decreased between 1990 and 1992, in 1992, the black-white ratio for neonaFrom the Departments of Obstetrics and Gynecology and Public Health Sciences, Wake Forest University School of Medicine, WinstonSalem, North Carolina. Supported by Grant NRO2410-01, National Institute of Nursing Research, National Institutes of Health.
656 0029-7844/98/$19.00 PII S0029-7844(98)00012-X
tal mortality, based on maternal race, was 2.5, an increase from a ratio of 2.4 in 1990. The ratio for postneonatal mortality remained at 2.3.3 In 1994, there was a LBW rate of 13.2% and a preterm delivery rate of 18.4% among blacks.4 Programs to reduce the incidence of preterm and/or LBW births that focus on risk assessment, client and provider education, and more frequent prenatal contacts showed promising results in populations of middle-class women5,6 and rural women,7,8 but these results were not replicated in subsequent randomized trials. Most randomized controlled trials in low-income populations in the United States, Europe, and Latin America have failed to demonstrate differences between intervention and control groups.9 –18 Home visits by midwives or registered nurses were the primary intervention in studies by Blonde et al14 in Paris, Villar et al15 in Latin America, and Olds et al10 in the United States. In the United Kingdom, home visits by a “family worker” who was a laywoman provided social support to reduce the level of stress.12 In each of these studies,10,12,14,15 the target population was a group of women identified as “high-risk” by relatively similar criteria. Telephones have been used by health care providers in the United States in a variety of ways to provide health information and health care. Telephone counseling from a nurse who provides advice and support has been an important part of some programs of preterm birth prevention in which home uterine activity monitoring has been used.19,20 One study21 suggests that the nursing telephone contact per se may be as effective in reducing LBW as home uterine activity monitoring. However, in a small randomized trial of women with a previous preterm birth, no difference was found between subjects who received daily telephone calls and control subjects.22 The importance of a nurturing relationship between a nurse and a pregnant woman in the outcome of preg-
Obstetrics & Gynecology
nancy has been suggested.5,9 In the model described by Herron and associates,5 a key feature was the close relationship of the project nurse with subjects. Olds et al10 found that young adolescents who were visited at home by nurses gave birth to infants who weighed an average of 395 g more (P 5 .02) than those who did not receive home visits. The hypothesis we tested was that low-income women who receive a single personal visit and telephone calls from a registered nurse between 24 and 37 weeks’ gestation will have a lower incidence of LBW and preterm births than women who do not receive calls.
Materials and Methods This study was a randomized trial and was approved by the Clinical Research Practice Committee of the Bowman Gray School of Medicine. Three groups of women in the community public clinic were included in the sample, based on low birth weight rates from the 2 years before initiation of the study. They were black women (all ages), white and “other” women with a preterm labor risk score of at least 7 on the Wake Forest University School of Medicine risk assessment tool,22,23 and white or “other” women 18 years of age or younger. All potential subjects spoke English. In addition, potential subjects needed access to a telephone, although not necessarily in their own home. Subjects were entered into the study between 22 and 32 weeks’ gestation. Random assignment was directed by the biostatistician. The words “phone” for the intervention group and “book” for the control group were placed in opaque envelopes that were numbered and sealed by the biostatistician, following a computer randomization table. Each nurse carried a box of sequentially numbered envelopes with her. Eligible women were identified weekly on an original list from the clinic records. Risk assessment was conducted as a part of normal clinic protocol. Contact was made by letter and followed by a telephone call to make an appointment for a personal visit from a nurse hired specifically for this study. If the woman did not have a telephone, efforts were made to contact her through family members or by leaving a note on her door. During the personal visit, the project was explained, and the woman was asked to sign a consent form. After consenting, each woman was interviewed to collect baseline data (health history and psychosocial assessment) and assigned to intervention or control groups by choosing the next sealed opaque envelope from a box prepared previously by the biostatistician. The interview with women in the control group concluded with information about a questionnaire they
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would receive in the mail at 34 weeks’ gestation and a $10 gift certificate they would receive if they returned the questionnaire. They also were given a booklet about preventing preterm labor; the same booklet was available in the clinic. Women in the intervention group received additional instruction about the signs of preterm labor, and a schedule was established for the time and frequency of telephone calls they would receive from the nurse, as well as instructions about contacting the nurse by telephoning her pager number. They were told about the 34-week questionnaire and that they would receive a $25 gift certificate at 37 weeks or after the birth of their baby, if they returned their assessment and remained in contact with the nurse by telephone. A tracking sheet was completed for every woman registered in the clinic list. Women were identified as eligible, accessible by telephone or not, agreeing to the personal visit for enrollment, participating in the enrollment visit, and randomized to the intervention or control group. A woman was dropped from the study if she moved from the community or if she transferred to another prenatal care provider. Nurse telephone calls were made on the schedule to which nurse and subject agreed, from the time of the home visit (22–32 weeks’ gestation) until the 37th week. The timing of the calls was designed to suit the woman’s convenience. The goal was three telephone contacts per week. Women without telephones could contact their primary nurse via the nurse’s pager when they were near a telephone. The nurse returned the call immediately. Although no formal script was followed, each telephone call addressed three major areas: assessment of health status (perception of uterine contractions and other pregnancy changes, color of urine as an assessment of hydration, number of meals eaten, number of cigarettes smoked, alcohol and drug use, and ingestion of a prenatal vitamin capsule on the previous day); recommendations based on assessment; and discussion of any additional issues important to the mother. The duration of each call was recorded. Three experienced nurses, hired specifically for the telephone intervention study, conducted the intake interviews and all of the telephone intervention. All of the nurses were white. These nurses did not attend clinic, nor did they have any further contact with subjects other than telephone calls after the initial home visit. Clinic personnel, including attending physicians, residents, nurses, and others were blinded to group assignment. If a referral to clinic, the labor suite, or another agency was needed, the nurse instructed the patient to make the call and then ascertained that the call was made. Data collection was done by an additional nurse hired specifically for this task. She did not participate in
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the intervention, was not present at any meetings during which patients were discussed, and was blinded to group assignment. Data were collected through interview at the personal visit and from the 34-week mailed assessment, prenatal records at the clinic and intrapartum and neonatal records at the hospital by a data collection nurse, and the logs kept by the intervention nurses. All data were collected on paper forms that were entered by trained data entry staff into a relational database system, which enforced range and data type restrictions. Data quality analysis was achieved with data quality check reporting, data audits, double-entry, and inter-rater reliability checks. The estimated date of confinement was calculated by the best available criteria: date of last menstrual period (LMP) when known, uterine size as determined at initial prenatal examination, and ultrasound measurements when indicated. Criteria for ultrasound measurements included unknown or uncertain LMP, an LMP that did not correlate with uterine size, and late entry into prenatal care. Antecedent variables in the intervention and control groups were compared by x2 test for categoric variables and two sample t tests for continuous variables. The primary outcomes of interest and difference in the rates of LBW infants and of births before 37 weeks were tested by calculating relative risks (RRs) and 95% confidence intervals (CIs). Comparisons were made between the control and intervention groups stratified by ethnicity (black versus white or other) and by age grouping (18 or younger versus 18) within ethnicity strata. With two outcome variables of interest (low birth weight status and premature status), this made eight comparisons. To account for multiple hypothesis tests, an appropriate correction was made to the nominal level of statistical significance (0.05/8 5 0.006). Only those comparisons with P values smaller than this were considered statistically significant. The target sample size was projected initially for a one-sided test. To achieve 80% power a 5 .05, a sample size of 1540 was required. In the final analysis, the more conservative two-sided test was used. Analysis was on an intentionto-treat basis.
Results Of the 3127 women eligible to participate by race and risk status, we were able to contact 1850 (59.2%). The principal reasons for inability to contact were lack of phone and/or lack of permanent address. Of the contacted women, 155 (8.38%) refused participation. Women contacted after 32 weeks because of late registration for prenatal care were not randomized. Only five women (0.03%) who consented to a home visit
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Table 1. Tracking Data
Enrolled in clinic Not eligible† Eligible Eligible not included‡ Randomized Intervention Control Dropped from final analysis§ Intervention Control Available for analysis Intervention Control Total
Black
White or other*
Total
2595 291 2304 1109
2635 1812 823 464
5230 2103 3127 1573
597 598
178 181
775 779
40 42
17 22
57 64
557 556 1113
161 159 320
718 715 1433
* Other represented 6.3% of clinic population, 0.8 of study sample. The majority of other (81.9%) were not eligible because they did not speak English. † Women were not eligible if they could not be contacted before 32 weeks’ gestation; were white, low risk, and older than 18 years; or did not speak English. ‡ Women were eligible by race and age but not included if they refused or could not be contacted before 32 weeks; the majority lacked a telephone. § Women were dropped from final analysis if they had a multiple gestation, moved out of town, or transferred to a private prenatal care provider.
refused to participate after the study was explained. Of the 1850 women contacted, 1554 (84%) agreed to participate and were randomized (Table 1). One hundred twenty-one randomized women (7.8%) changed health care providers, moved from the community, or had multiple gestation pregnancies, leaving 1433 subjects for the analysis of singleton birth outcomes. No significant differences were found between the randomized groups in age, single marital status, educational level, number of pregnancies, Medicaid eligibility, preterm labor risk score, previous LBW birth, smoking, use of illicit drugs or alcohol during pregnancy, physical abuse during the current pregnancy, job requiring heavy physical work, self-reported constant or frequent high-stress state anxiety, interconceptional period less than a year, maternal age at entry into the study, total number of prenatal care visits, or weight gain during pregnancy. For white and other women only, there was a difference in physical abuse before pregnancy (32.5% in the intervention group versus 44% in the control group, P 5 .031), presumably on the basis of chance. Subgroup analyses by race (black versus white or other) and age (18 or younger versus 19 or older) were conducted for several variables. The mean gestational age at entry into the study ranged from 25.8 weeks for white subjects 18 years of age or younger to 26.7 weeks for black subjects 18 years of age or younger. There was
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Table 2. Birth Weight and Gestational Age by Race and Age of Mother
Black women Weight ,2500 g Age #18 y (n 5 353) Age $19 y (n 5 759) Gestational age ,37 wk Age #18 y (n 5 353) Age $19 y (n 5 759) White or other women Weight ,2500 g Age #18 y (n 5 213) Age $19 y (n 5 107)‡ Gestational age ,37 wk Age #18 y (n 5 213) Age $19 y (n 5 107)‡
Intervention* %
Control† %
RR
95% CI
P
11.3 11.0 11.4 9.4 11.0 8.7
15.3 11.6 17.3 12.8 7.9 15.4
.75 .95 .66 .73 1.39 .56
0.55, 1.00 0.53, 1.72 0.46, 0.94 0.52, 1.02 0.72, 2.67 0.38, 0.84
.047 .874 .020 .064 .039 .004
9.9 7.0 17.4 11.2 7.8 19.6
10.0 6.1 14.8 5.0 4.1 6.6
0.99 1.14 1.18 2.37 1.92 2.99
0.48, 2.05 0.41, 3.16 0.49, 2.82 1.00, 5.62 0.61, 6.02 0.98, 9.09
.879 .807 .712 .044 .255 .041
RR 5 relative risk; CI 5 confidence interval. * The intervention group comprised 557 black women and 161 white women. † The control group comprised 556 black women and 159 white women. ‡ The white-other sample of women $19 years of age includes only women identified as at higher risk for preterm birth; all black women were eligible for inclusion.
no difference between intervention and control groups in age of entry into the study for any subgroup nor was there a difference for any subgroup in the number of pregnancies, births, and abortions. There was no significant difference in subgroups in the median number of calls to each woman (21 to black women 18 years of age or younger and white women in either age group, and 25 to black women 19 years of age and older; P 5 .193). The median number of minutes per call was 3.6 minutes for black women 18 years of age or younger, 3.4 minutes for black women 19 years of age or older, 3.2 minutes for white women 18 years of age or younger, and 3.7 minutes for white women 19 years of age or older (P 5 .802). For the total sample, LBW rates were 10.9% in the intervention group and 14.0% in controls (RR .75; 95% CI, 0.55, 1.03; P 5 .072). For gestational age less than 37 weeks, rates were 9.7 in the intervention group and 11.0 in the controls (RR .87; 95% CI, 0.62, 1.22; P 5 .415). However, among black women, there was a 26% difference in LBW rates between the intervention (11.3%) and control (15.3%) groups (RR .75; 95% CI 0.55, 1.00; P 5 .048) (Table 2). This difference came almost entirely from the subgroup of black women 19 years of age and older; in this subgroup, there was a 34% difference between the intervention and control groups (11.4% and 17.3%; RR .66; 95% CI 0.46, 0.94; P 5 .020). Similarly, a 27% decrease in births at gestational ages before 37 weeks was found among black women in the intervention group (9.4%) compared with those in the control group (12.8%) (RR .73; 95% CI 0.52, 1.02; P 5 .066). Among women 19 years of age and older, the differences in LBW birth were 34% (11.4% versus 17.3%; RR
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.66; 95% CI 0.46, 0.94; P 5 .02). For preterm birth, the difference was 44% (8.7% versus 15.4%; RR .56; 95% CI 0.38, 0.84; P 5 .004). We were concerned about the higher rates of preterm birth in the subgroup of white women 19 years of age or older in the intervention group (19.6%) compared with those in the control group (6.6%). In subgroup analyses, there were no differences in the intervention and control groups, except for cigarette smoking. In the intervention group, 41 of 47 (87.2%) were smokers compared with 46 of 65 (70.8%) in the control group (P 5 .039). Moreover, 75% of the intervention group smoked more than ten cigarettes each day compared with 61% of the control group. When we examined the smokingintervention interaction effect, the odds ratio (OR) for LBW births was 40% lower for nonsmokers than for smokers (P 5 .12). For birth before 37 weeks, the OR was 53% lower (P 5 .04). We examined differences in both LBW and preterm births outcome among high- and low-risk women of both racial and age groups. No statistically significant difference existed except for preterm birth among lowrisk black women older than 19 years old (5.7% for intervention versus 11.51% for control; P 5 .027).
Discussion The findings in this study are inconclusive as to the benefits of telephone intervention. For the total sample, there was no difference between intervention and control groups. However, the intervention was effective in the largest subgroup (black women 19 years and older) but not in black teens or white women. There are
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several possible reasons. First, the black and whiteother groups were not similar. In the group of black women, the whole population was eligible, rather than a high-risk subset of the population. All black women receiving care at the target clinic were eligible for inclusion; among women of white or other raceethnicity, only those who were identified as high-risk on the risk assessment form or were 18 years of age and younger were included. Second, LBW and preterm birth rates have been higher historically in black and white-other populations, with the difference increasing in recent years. Higher rates of preterm birth in white women 19 years and older in the intervention group were of particular concern. The only variable that was associated with this high rate of prematurity was cigarette smoking. Although cigarette smoking was a focus of the telephone intervention, and there was a reduction in smoking, the intervention did not begin until 24 weeks (median 26 weeks), and the reduction or cessation in smoking came in the third trimester. That 87% of women in this subgroup were still smoking, with 75% smoking more than ten cigarettes a day at the time of enrollment late in the second trimester, suggests that intervention directed at smoking cessation during prenatal visits had minimal effects. The lack of difference in young black women, 18 years of age and younger, was not due to increased rates in the intervention group but to rates in the control group comparable to the intervention groups in both age groupings. Rates among black women in the intervention group were virtually identical for both age groups (11.0 for ages up to 18 and 11.4 for ages 19 and older), but rates in the control groups were markedly different (11.6 for ages up to 18 and 17.3 for ages 19 and older). Rates were lower for teens of white or other race-ethnicity (7.0 in the intervention group and 6.1 in the control group) than black teens, but there was no significant difference between the intervention and control groups. Strong community support for pregnant teens, including an optional high school program with daily classes by a nurse focusing on pregnancy and parenting, may have provided the extra education and support to teens in the control group. In contrast, black women 19 years of age and older, lacking that support, appeared to benefit most from the extra education and support of the telephone intervention. When we examined the data by risk status, we found that most of our reduction in LBW was in women who were identified at low risk on the preterm labor risk assessment. It would be interesting to test the effects of this program in low-risk white women. For a number of years, the main focus of many preterm labor programs has been on women identified as high risk on various
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but similar risk assessment instruments. One of the frustrations with risk assessment has been the failure to identify approximately 50% of women who deliver preterm and/or LBW infants. A population-based program with increased attention to women without traditional risk factors in the black community may be one strategy to address high rates of LBW births in this population. This study raises at least four questions. First, would more frequent calls have enhanced the results? Although our goal was three calls per week, and three calls were attempted, only half of the calls, approximately 1.5 per week (21.7 over 14 weeks) were completed. The mean is only slightly affected by those women delivering earlier because of the small numbers in those groups. The mean number of minutes per patient for women who delivered between 31 and 36 weeks was 75.2 compared with 74.3 for women delivering after 37 weeks. Second, would telephone intervention be equally successful in a broader population that includes women with increased income and educational levels? Yawn and Yawn7 made a major impact on this population through office-based education. Third, what effect would the intervention have had on low-income women of white or other race-ethnicity 19 years of age and older who did not have medical risk factors? These women were not included in the original design, because their rates of LBW and preterm birth were lower than those of other population subgroups in the target clinic. In the sample of black women for this study, which was based in the total clinic population, there was a significant decrease in preterm birth between low-risk women in the intervention and control groups. Although rates of LBW and preterm birth are lower in women of white or other race-ethnicity than in black women, even a small reduction would be worthwhile. Fourth, how would a telephone intervention compare with a program of home visiting? Telephone intervention is clearly more cost effective. We estimated the cost of 14 weeks of telephone intervention to be similar to the cost of a single home visit when travel costs and time as well as visit time were included. Certain activities (blood pressure evaluation, for example) usually require home visiting. Studies designed to answer these questions may improve our ability to reduce preterm and LBW birth.
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2. Schoendorf KC, Hogue C, Kleinman J, Rowery D. Mortality among infants of black as compared with white college-educated parents. N Engl J Med 1992;26:1522– 6. 3. Guyer B, Strabino D, Ventura S, Singh G. Annual summary of vital statistics—1994. Pediatrics 1994;96:1029 –39. 4. Ventura S, Martin J, Toffel S, Matthews T, Clarke S. Advance report of final mortality statistics, 1992. Monthly Vital Statistics Report; vol. 43, no. 5. Hyattsville, Maryland: Public Health Service, 1994: 1– 87. 5. Herron M, Katz V, Creasy R. Evaluation of a preterm birth prevention program: A preliminary report. Obstet Gynecol 1982; 59:452–5. 6. Fangman JJ, Mark PM, Pratt L, Conway KK, Healey ML, Oswald JW, et al. Prematurity prevention programs: An analysis of successes and failures. Am J Obstet Gynecol 1994;170:744 –50. 7. Yawn BP, Yawn RA. Preterm birth prevention in a rural practice. JAMA 1989;262:230 –3. 8. Moore ML, Buescher P, Meis P, Michielutte R, Ernest JM, Sharp P. The effect of a preterm prevention program in 17 rural and 3 urban counties in northwest North Carolina. J Rural Health 1989;5:361– 70. 9. Main D, Gabbe S, Richardson D. Can preterm births be prevented? Am J Obstet Gynecol 1985;151:892– 8. 10. Olds D, Henderson C, Tatelbaum R, Chamberlin R. Improving the delivery of prenatal care and outcomes of pregnancy: A randomized trial of nurse home visitation. Pediatrics 1986;77:16 –28. 11. Mueller-Heubach E, Reddick D, Barrett B, Bente R. Preterm birth prevention: Evaluation of a prospective controlled randomized trial. Am J Obstet Gynecol 1989;160:1172– 8. 12. Spencer B, Thomas H, Morris J. A randomized controlled trial of the provision of a social support service during pregnancy; the South Manchester Family Worker Project. Br J Obstet Gynaecol 1989;96:281– 8. 13. Goldenberg R, Davis R, Copper R, Carbiss D, Andrews J, Carpenter A. The Alabama preterm birth prevention project. Obstet Gynecol 1990;75:933–9. 14. Blondel B, Breart G, Glado J, Chartier M. Evaluation of the home-visiting system for women with threatened preterm labor: Results of a randomized controlled trial. Eur J Obstet Gynecol Reprod Med 1990;34:47–58. 15. Villar J, Farnot U, Barros F, Victora C, Langer A, Belezan J. A randomized trial of psychosocial support during high-risk pregnancies. N Engl J Med 1992;327:1266 –71.
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16. Collaborative Group on Preterm Birth Prevention. Multicenter randomized, controlled trial of a preterm birth prevention program. Am J Obstet Gynecol 1993;169:352– 66. 17. Hobel C, Ross M, Bomis R, Bragonier JR, Nessim S, Sandhu M, et al. The West Los Angeles preterm birth prevention project. Am J Obstet Gynecol 1994;170:54 – 62. 18. Collaborative Group on Preterm Birth Prevention. Multicenter randomized, controlled trial of a preterm birth prevention program. Am J Obstet Gynecol 1993;169:352– 66. 19. Katz V, Gill PJ, Newman RB. Assessment of uterine activity in ambulatory patients at high risk of preterm labor and delivery. Am J Obstet Gynecol 1986;154:44 –7. 20. Morrison J, Martin JN, Martin RW, Gookin KS, Wiser WL. Prevention of preterm birth by ambulatory assessment of uterine activity: A randomized study. Am J Obstet Gynecol 1987;156:536 – 43. 21. Iams JD, Johnson F, O’Shaughnessy RW. A prospective randomized trial of home uterine activity monitoring in pregnancies at increased risk of preterm labor. Am J Obstet Gynecol 1988;159:595– 603. 22. Ernest JM, Michielutte R, Meis P, Moore ML, Sharp P. Identification of women at high risk for preterm low birthweight births. Prev Med 1988;17:60 –72. 23. Michielutte R, Ernest JM, Moore ML, Meis P, Sharp P, Wells HB, et al. A comparison of risk assessment models for term and preterm low birthweight. Prev Med 1992;21:98 –103.
Address reprint requests to:
Mary Lou Moore, PhD, RNC Department of Obstetrics and Gynecology Wake Forest University School of Medicine Winston-Salem, NC 27157-1066 E-mail: [email protected]
Received September 15, 1997. Received in revised form December 9, 1997. Accepted January 8, 1998. Copyright © 1998 by The American College of Obstetricians and Gynecologists. Published by Elsevier Science Inc.
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