- Email: [email protected]
Perinatal outcome in pregnancy complicated by massive obesity
Perinatal outcome in pregnancy complicated by massive obesity Jordan H. Perlow, MD, Mark A. Morgan, MD, Douglas Montgomery, MD, Craig V. Towers, MD, and Manuel Porto, MD Long Beach and Orange, California OBJECTIVE: Our objective was to determine the impact of massive obesity during pregnancy, defined as maternal weight >300 pounds, on perinatal outcome. STUDY DESIGN: A case-controlled study was conducted. Between Jan. 1, 1986, and Dec. 31, 1990, 111 pregnant women weighing >300 pounds who were delivered at Long Beach Memorial Women's Hospital were identified with a perinatal data base search. A control group matched for maternal age and parity was selected, and perinatal variables were compared between groups. To control for potential confounding medical complications, massively obese patients with diabetes and lor chronic hypertension antedating the index pregnancy were excluded from the obese group, and the data were reanalyzed. The Student t test x 2, and Fisher's exact statistical analysis were used where appropriate. RESULTS: MaSSively obese pregnant women are significantly more likely to have a multitude of adverse perinatal outcomes, including primary cesarean section (32.4% vs 14.3%, P = 0.002), macrosomia (30.2% vs 11.6%, P = 0.0001), intrauterine growth retardation (8.1 % vs 0.9%, P = 0.03), and neonatal admission to the intensive care unit (15.6% vs 4.5%, P = 0.01). They also are significantly more likely to have chronic hypertension (27.0% vs 0.9%, P < 0.0001) and insulin-dependent diabetes mellitus (19.8% vs 2.7%, P = 0.0001). However, when those massively obese pregnant women with diabetes and lor hypertension antedating pregnancy are excluded from analysis, no statistically significant differences in perinatal outcome persisted. CONCLUSION: Massively obese pregnant women are at high risk for adverse perinatal outcome; however, this risk appears to be related to medical complications of obeSity. (AM J OasTET GVNECOL 1992;167:958-62.)
Key words: Massive obesity, pregnancy, perinatal outcome Obesity, an excess amount of body fat, frequently results in significant impairment of health.' The National Health and Nutrition Examination Survey II study found that 25.6% of Americans are obese! Obesity is of particular interest and importance to those providing health care to women, because age-adjusted rates of obesity for females of all races significantly exceeds those for males.2.3 Thus the problem of obesity is one that beckons further research among obstetrician-gynecologists. The impact of obesity during pregnancy has been the subject of several investigations of varying design and outcome.··'2 This body of literature remains controversial with respect to the influence of obesity on From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Long Beach Memorial Medical Center Women's Hospital, and the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of California, Irvine, UCI Medical Center. Presented at the Twelfth Annual Meeting of the Society of Perinatal Obstetricians, Orlando, Florida, February 3-8, 1992. Reprint requests: Jordan H. Perlow, MD, Associate Director, Maternal-Fetal Medicine, Phoenix Perinatal Associates, 1300 N. 12th St., Suite 320, Phoenix, AZ 85006. 616139589
958
perinatal outcome. Problems inherent to the interpretation of these studies include the lack of uniformity in defining obesity, with the terms grotesque, massive, morbid, and severe used to categorize this disorder, the perinatal variables studied; and the lack of controlling for confounding variables of maternal age, parity, and medical complications. With an understanding of the immense problems obesity inflicts on the general health of reproductiveaged patients,'3.'7 we sought to determine the impact of massive obesity (weight >300 pounds during pregnancy) in our patient population. Our hypothesis was that perinatal outcome in these patients would be markedly compromised.
Material and methods A computerized perinatal data base search was performed to identify patients delivered at Long Beach Memorial Medical Center Women's Hospital between Jan. I, 1986, and Dec. 31,1990, with a maternal weight of >300 pounds during pregnancy. Instances where the same obese patient delivered twice during the study period were managed by analyzing only the most recent pregnancy. Selected maternal, fetal, and neonatal out-
Volume 167 Number 4, Part I
Massive obesity and perinatal outcome
959
Table I. Maternal descriptive variables Obese
Total (n
Parameter
Age (yr) Parity Weight (Ib)
= 111)
29.7 ± 5.7 (19-50) 1.3 ± 1.5 (0-8) 333.8 ± 48.9 (300-415)
Excluding diabetes mellitus or chronic hypertension (n = 82)
Control (n
28.9 ± 5.2 (19-45) 1.1 ± 1.3 (0-6) 334.7 ± 57.8 (300-415)
= 111)
29.8 ± 5.3 (19-41) 1.3 ± 1.4 (0-6) 167.4 ± 32.5 (110-273)
P Value NS NS <0.0001*
NS, Not statistically significant. Values in parentheses are ranges. *Difference between obese and control groups.
Table II. Perinatal outcome: Maternal medical complications
p
Variable
Obese (n = 111)
Control (n = 111)
Value
Odds ratio
95% Confidence interval
Diabetes mellitus Gestational diabetes Chronic hypertension Preeclampsia
19.8 5.4 27.0 4.5
2.7 0.9 0.9 0
0.0001 0.12 <0.0001 0.058
9.0 6.3 40.7
2.4-27.3 0.7-65.6 5.8-155.6
come variables were studied in each of these pregnancies by data base and patient chart review. Maternal demographic variables included maternal age, parity, and weight. Preexisting maternal medical complications (insulin-dependent diabetes mellitus and chronic hypertension) and obstetric complications (twinning, preeclampsia, gestational diabetes, abruptio placentae, placenta previa, presence of meconium, and intrauterine fetal death) were reviewed. Cesarean section and preterm delivery rates and the neonatal variables of Apgar score, birth weight, and admission to the neonatal intensive care unit were also determined. These outcome variables were also collected from a control group matched for maternal age, parity, and time of delivery. Each matched control pregnancy was consecutively selected from the birth log after each index (massively obese) delivery. The outcome variables were then compared between groups. To control for confounding medical conditions associated with obesity, massively obese patients with a diagnosis of insulinrequiring diabetes mellitus and/ or chronic hypertension antedating the index pregnancy were removed and the perinatal outcome variables reanalyzed for this subset. Differences in demographic and perinatal variables were evaluated with a two-tailed Student t test, X2, and Fisher's exact test, where appropriate. The significance level was set at u = 0.05.
Results One hundred eleven massively obese pregnant women (weight >300 pounds during pregnancy) were identified during the study period among 25,636 consecutive deliveries (incidence 0.43%). One hundred eleven controls were selected as stated above. Data base
information and patient charts were available for all patients. Maternal descriptive variables are presented in Table 1. The mean maternal weight in the massively obese group was significantly greater than in the control group (p < 0.00001). By study design no significant differences were observed among the matched variables, age and parity, between the two groups. Although four sets of twins were delivered among the massively obese pregnant women, twinning was not observed in the control group (difference not statistically significant). Table II illustrates the occurrence of maternal medical complications of pregnancy between groups. The massively obese pregnant women were significantly more likely to be delivered by cesarean section (Table III). The overall cesarean section rate for the massively obese group was nearly double that of the control group (p = 0.0002). The primary cesarean section rate for massively obese pregnant women was also significantly increased (p = 0.002). No differences in the occurrence of placenta previa, abruptio placentae, or preterm delivery (delivery before 36 completed weeks gestation) were observed between groups. Table IV illustrates differences in neonatal outcome variables between groups. Neonates born to massively obese pregnant women were significantly more likely to exhibit both low birth weight (birth weight <2500 gm, p = 0.02) and macrosomia (birth weight >4000 gm, p = 0.0001). An increased frequency of intrauterine growth retardation (birth weight < 10th percentile for population) was also observed in the massively obese group (p = 0.03). Neonates born to massively obese pregnant women had I-minute Apgar scores more often <5 (p = 0.04); however, this difference did not
960
Perlow et al.
October 1992 Am J Obstet Gynecol
Table III. Perinatal outcome: Delivery variables Control (n = 111)
Obese Outcome
Cesarean section, overall Cesarean section, primary Cesarean section, cephalopelvic disproportion Cesearean section, fetal distress Delivery <36 wk
(n
= 111)
Odds ratio
95% Confidence interval
55.9 32.4 25.4
30.6 14.4 8.8
0.0003 0.003 0.12
2.9 2.9 3.3
1.6-5.2 1.4-5.9 0.8-14.6
22.0
17.6
0.90
1.2
0.4-4.2
13.5
8.1
0.28
1.8
0.7-4.6
Values expressed as percent.
Table IV. Perinatal outcome: Neonatal variables Outcome
Apgar score at 1 min <5 Apgar score at 5 min <7 Birth weight >4500 gm Birth weight >4000 gm Birth weight <2500 gm Intrauterine growth retardation Admitted to neonatal intensive care unit
p
Obese (n = 115)
Control (n = 111)
Value
Odds ratio
95% Confidence interval
13.0 7.8 13.0 30.4 14.7 7.8
4.5 2.7 1.8 10.8 4.5 0.9
0.04 0.16 0.003 0.0005 0.02 0.03
3.2 3.0 8.1 3.6 3.6 9.3
1.1-10.3 0.7-14.2 1.7-32.8 1.7-7.9 1.2-11.9 1.2-67.9
15.6
4.5
0.01
3.9
1.3-12.6
Values expressed as percent. For obese category n
=
115 because of four twin sets.
persist at 5 minutes. Interestingly, these neonates were also more likely to require admission to the neonatal intensive care unit (p = 0.01). To determine if significant differences in perinatal outcome were due to obesity per se or to medical complications more frequently observed in the massively obese group, the data were reanalyzed after excluding 29 massively obese patients with the diagnosis of chronic hypertension or insulin-requiring diabetes mellitus antedating pregnancy. The mean maternal age and parity for this group was again not significantly different from the control group (Table I). Mean maternal weight for this group was not significantly different from the overall massively obese group but was markedly different from controls (p < 0.0001). Without exception, no statistically significant differences in perinatal outcome were observed when the data were analyzed in this manner (Table V).
Comment The influence of obesity on the degradation of health is the subject of a wide body of literature. 13-2o Much is known regarding the obese individual's increased risk for coronary artery disease, diabetes mellitus, stroke, and cancer. However, much less is known regarding the impact of obesity on perinatal outcome. This study reports the perinatal outcome for a group of obese patients with a degree of obesity not previously reported in the literature. Our data analysis, with re-
spect to overall perinatal outcome and outcome between groups, excluding the obese patients with insulin-dependent diabetes mellitus or chronic hypertension, is also unique to the literature. We chose a pregnancy weight of >300 pounds to define massive obesity. This definition is random, because unfortunately a standardized nomenclature does not exist. However, obesity is commonly defined in terms of the body mass index (weight [kg]/height [m 2 ]) or percent ideal body weight (percent weight in relation to "ideal" weight determined from actuarial tables). \5 Obesity during pregnancy has been defined in a multitude of ways: as prepregnancy weight >200 pounds),'" > 120%8.10 or > 110% (mean obese weight 171 pounds), \I ideal body weight at first prenatal visit, gravid weight >90 kg,9 and body mass index >30. 13 Recently, Wolfe et al!1 reported no benefit in the use of maternal body mass index over the gravid weight in the risk assessment of outcomes related to maternal weight. Massive and morbid obesity have been defined as pregnancy weight >250 pounds,' prepregnancy weight 150% ideal body weight,"-Io morbid obesity as 200% ideal body weight, and grotesque obesity as three times "accepted desirable weight."6 This lack of uniformity makes interpreting the literature as a whole virtually impossible, emphasizing the importance of understanding the definitions used, populations studied, and outcome variables assessed in each study. We found a remarkable higher frequency of chronic
Massive obesity and perinatal outcome
Volume 167 Number 4, Part I
961
Table V. Perinatal outcome excluding massively obese with insulin-dependent diabetes mellitus and chronic hypertension Outcome
Cesarean section Primary cesarean section Apgar score at 1 min <5 Apgar score at 5 min <7 Birth weight >4500 gm Birth weight >4000 gm Birth weight <2500 gm Intrauterine growth retardation Admitted to neonatal intensive care unit
Obese (n = 82)
Control (n = 111)
42.7 19.5 4.9 2.4 3.7 14.6 3.7 4.9
30.6 14.4 4.5 2.7 1.8 11.7 4.5 0.9
4.9
1.9
Odds atio
95% Confidence interval
0.12 0.89 0.73 0.70 0.73 0.70 0.94 0.82
1.7 0.9 2.1 1.3 2.1 1.3 0.8 l.l
0.9-3.2 0.3-2.7 0.3-130.0 0.5-3.2 0.3-130.0 0.5-3.2 0.5-4.0 0.3-4.9
0.21
5.6
0.6-83.0
Values expressed as percent.
hypertension (27.0% vs 17.2%) and diabetes mellitus (19.8% vs 10.4%) in our massively obese group when compared with the morbidly obese group (> 150% ideal body weight) reported by Garbaciak et al.,10 although no differentiation was made between gestational and insulin-dependent diabetics. This observation may be related to the more obese population we studied, and these findings are consistent with the known increased association of these medical conditions with increasing "degrees" of obesity. 14·20. 22 In contrast to other studies demonstrating an increased risk of gestational diabetes,7. 12 we were unable to show such an association. Because these obese patients were multiparous and relatively older, it may be that they had previously been gestational diabetics and eventually were diagnosed as insulin-dependent by the time the index pregnancy occurred. This may also account for the high frequency of insulin-dependent diabetes observed in this group (Table II). In spite of a 27% frequency of chronic hypertension in our massively obese group, we were unable to demonstrate a statistically significant increased frequency of preeclampsia in this group. This is in contrast to previous observations!' 5. 7 However, a strong trend was present (p = 0.058), and with larger numbers significance might be met (Table II). We demonstrated significantly increased overall and primary cesarean section rates in the massively obese group (Table III). This is consistent with some9. 10. 12 but not alF- 9 reports. These differences were not observed to persist when the massively obese diabetics and hypertensives were removed from data analysis (Table V). This suggests that obesity per se does not lead to an increased risk of cesarean section but rather to the inherent increased risk of medical complications of pregnancy described. Garbaciak et al. 10 reported an increase in the primary cesarean section rate for morbidly obese patients after patients with antepartum complications were removed from data analysis. However, he re-
ported a frequency of chronic hypertension of 17.2% and of diabetes mellitus 10.4%. Removing fewer patients with these complications may not be expected to change the frequency of cesarean delivery. The finding of increased cesarean section rates for this population is particularly important when one considers the increased operative morbidity described for the obese patient population. 23 Before controlling for chronic hypertension and insulin-dependent diabetes mellitus, we found a significantly increased frequency of both low birth weight and macrosomic neonates in the massively obese group. Macrosomia is a rather consistent finding in pregnancy complicated by obesity" 5. 7·9. 12 and may be related to the increased frequency of diabetes (both gestational and insulin requiring) seen in this population. In contrast, patients with chronic hypertension and classes of diabetes associated with vasculopathy and nephropathy are at increased risk for low birth weight and intrauterine growth retardation. 24 • 25 The high frequency of chronic hypertension and insulin-dependent diabetes mellitus in our massively obese population could certainly account for these findings, because these differences were not apparent when these medical complications were controlled for (Table V). Our observation that neonates of the massively obese pregnant women were more frequently admitted to the neonatal intensive care unit is indicative of the high obstetric risk factors of chronic hypertension and insulin-dependent diabetes mellitus and not necessarily due to obesity in and of itself (Tables IV and V). Therefore it appears that pregnant women with a pregnancy weight> 300 pounds are at an increased risk for a multitude of adverse perinatal outcomes. Particularly striking is the enormously increased risk of chronic hypertension and diabetes mellitus in these patients, the higher rates of cesarean delivery and adverse neonatal outcomes, including low birth weight, intrauterine growth retardation, and admission to the neo-
962
Perlow et al.
natal intensive care unit. However, the present findings indicate that the massively obese pregnant women without chronic hypertension or insulin-dependent diabetes mellitus may experience normal perinatal outcome. These data may be useful in preconceptual and prenatal counseling and in the perinatal management of the massively obese pregnant woman. REFERENCES 1. Burton BT, Foster WR, Hirsch], Van Itallie TB. Health implications of obesity: an NIH consensus development conference. Int] Obesity 1985;9:155-69. 2. McDowell A, Engel A, Massey ]T, Maurer K. Plan and operation of the second National Health and Nutrition Examination Survey, 1976-1980. Hyattsville, Maryland: National Center for Health Statistics, 1981; DHHS publication no (PHS)81-1317. (Vital and health statistics; series I, no 15.) 3. National Center for Health Statistics. Anthropometric reference data and prevalence of overweight, United States, 1976-1980. Hyattsville, Maryland: National Center for Health Statistics, 1987; DHHS publication no (PHS)871688. (National Health Survey; series II, no 238.) 4. Odell LD, Mengert WF. The overweight obstetric patient. ]AMA 1945;128:87-90. 5. Tracy TA, Miller GL. Obstetric problems of the massively obese. Obstet Gynecol 1969;33:204-8. 6. Freedman MA, Preston LW, George WM. Grotesque obesity: a serious complication of labor and delivery. South Med] 1972;65:732-6. 7. Edwards LE, Dickes WF, Alton IR, Hadanson EY. Pregnancy in the massively obese: course, outcome and obesity prognosis of the infant. AM ] OBSTET GYNECOL 1978;131:479-83. 8. Harrison GG, Udall]N, Morrow III G. Maternal obesity weight gain in pregnancy, and infant birth weight. AM] OBSTET GYNECOL 1980;136:411-2. 9. Gross T, Sokol R], King K. Obesity in pregnancy: risks and outcome. Obstet Gynecol 1980;56:446-50. 10. Garbaciak]A]r, Richter M, Miller S, Barton]]. Maternal weight and pregnancy complications. AM] OBSTET GyNECOL 1985; 152:238-45. II. Mitchell MC, Lerner E. A comparison of pregnancy out-
October 1992 Am J Obstet Gynecol
12. 13. 14.
15.
16.
17. 18. 19. 20. 21. 22. 23. 24.
25.
come in overweight and normal weight women.] Am Coli Nutr 1989;8:617-24. Johnson SR, Kolberg BH, Varner MW, Railsback LD. Maternal obesity and pregnancy. Surg Gynecol Obstet 1987;164:431-7. Naeye RL. Maternal body weight and pregnancy outcome. Am] Clin Nutr 1990;52:273-9. Public Health Service. Healthy people 2000, national health promotion and disease prevention objectives. Washington: US Department of Health and Human Services, 1990; DHHS publication no (PHS)90-50212. Public Health Service. The Surgeon General's report on nutrition and health. Washington: US Department of Health and Human Services, 1988. DHHS publication no (PHS)88-5021O. Hubert HB, Feinleib M, McNamara PM, Castelli WP. Obesity as an independent risk factor for cardiovascular disease: a 26-year follow-up of participants in the Framingham Heart Study. Circulation 1983;67:968-77. Williamson DF, Kahn HS, Byers T. The 10-y incidence of obesity and major weight gain in black and white US women aged 30-55 y. Am] Clin Nutr 1991;53:1515-8S. Lew EA, Garfinkel L. Variations in mortality by weight among 750,000 men and women. ] Chronic Dis 1979;32:563-76. Garfinkel L. Overweight and cancer. Ann Intern Med 1985; 103: 1034-6. Kral ]G. Morbid obesity and related health risks. Ann Intern Med 1985;103:1043-7. Wolfe HM, Zador IE, Gross TL, Martier SS, Sokol RJ. The clinical utility of maternal body mass index in pregnancy. AM] OBSTET GYNECOL 1991;164:1306-10. Bray GA. Complications of obesity. Ann Intern Med 1985;104: 1052-62. Wolfe HM, Gross TL, Sokol R], Bottoms SF, Thompson KL. Determinants of morbidity in obese women delivered by cesarean. Obstet Gynecol 1988;71:691-6. Main DM, Main EK. Preterm birth. In: Gabbe SG, Niebyl ]R, Simpson ]L, eds. Obstetrics: normal and problem pregnancies. ed 2. New York: Churchill Livingstone, 1991:838. Gabbe SG. Intrauterine growth retardation. In: Gabbe SG, Niebyl ]R, Simpson ]L, eds. Obstetrics: normal and problem pregnancies. ed 2. New York: Churchill Livingstone, 1991 :926.
Key words: Massive obesity, pregnancy, perinatal outcome Obesity, an excess amount of body fat, frequently results in significant impairment of health.' The National Health and Nutrition Examination Survey II study found that 25.6% of Americans are obese! Obesity is of particular interest and importance to those providing health care to women, because age-adjusted rates of obesity for females of all races significantly exceeds those for males.2.3 Thus the problem of obesity is one that beckons further research among obstetrician-gynecologists. The impact of obesity during pregnancy has been the subject of several investigations of varying design and outcome.··'2 This body of literature remains controversial with respect to the influence of obesity on From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Long Beach Memorial Medical Center Women's Hospital, and the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of California, Irvine, UCI Medical Center. Presented at the Twelfth Annual Meeting of the Society of Perinatal Obstetricians, Orlando, Florida, February 3-8, 1992. Reprint requests: Jordan H. Perlow, MD, Associate Director, Maternal-Fetal Medicine, Phoenix Perinatal Associates, 1300 N. 12th St., Suite 320, Phoenix, AZ 85006. 616139589
958
perinatal outcome. Problems inherent to the interpretation of these studies include the lack of uniformity in defining obesity, with the terms grotesque, massive, morbid, and severe used to categorize this disorder, the perinatal variables studied; and the lack of controlling for confounding variables of maternal age, parity, and medical complications. With an understanding of the immense problems obesity inflicts on the general health of reproductiveaged patients,'3.'7 we sought to determine the impact of massive obesity (weight >300 pounds during pregnancy) in our patient population. Our hypothesis was that perinatal outcome in these patients would be markedly compromised.
Material and methods A computerized perinatal data base search was performed to identify patients delivered at Long Beach Memorial Medical Center Women's Hospital between Jan. I, 1986, and Dec. 31,1990, with a maternal weight of >300 pounds during pregnancy. Instances where the same obese patient delivered twice during the study period were managed by analyzing only the most recent pregnancy. Selected maternal, fetal, and neonatal out-
Volume 167 Number 4, Part I
Massive obesity and perinatal outcome
959
Table I. Maternal descriptive variables Obese
Total (n
Parameter
Age (yr) Parity Weight (Ib)
= 111)
29.7 ± 5.7 (19-50) 1.3 ± 1.5 (0-8) 333.8 ± 48.9 (300-415)
Excluding diabetes mellitus or chronic hypertension (n = 82)
Control (n
28.9 ± 5.2 (19-45) 1.1 ± 1.3 (0-6) 334.7 ± 57.8 (300-415)
= 111)
29.8 ± 5.3 (19-41) 1.3 ± 1.4 (0-6) 167.4 ± 32.5 (110-273)
P Value NS NS <0.0001*
NS, Not statistically significant. Values in parentheses are ranges. *Difference between obese and control groups.
Table II. Perinatal outcome: Maternal medical complications
p
Variable
Obese (n = 111)
Control (n = 111)
Value
Odds ratio
95% Confidence interval
Diabetes mellitus Gestational diabetes Chronic hypertension Preeclampsia
19.8 5.4 27.0 4.5
2.7 0.9 0.9 0
0.0001 0.12 <0.0001 0.058
9.0 6.3 40.7
2.4-27.3 0.7-65.6 5.8-155.6
come variables were studied in each of these pregnancies by data base and patient chart review. Maternal demographic variables included maternal age, parity, and weight. Preexisting maternal medical complications (insulin-dependent diabetes mellitus and chronic hypertension) and obstetric complications (twinning, preeclampsia, gestational diabetes, abruptio placentae, placenta previa, presence of meconium, and intrauterine fetal death) were reviewed. Cesarean section and preterm delivery rates and the neonatal variables of Apgar score, birth weight, and admission to the neonatal intensive care unit were also determined. These outcome variables were also collected from a control group matched for maternal age, parity, and time of delivery. Each matched control pregnancy was consecutively selected from the birth log after each index (massively obese) delivery. The outcome variables were then compared between groups. To control for confounding medical conditions associated with obesity, massively obese patients with a diagnosis of insulinrequiring diabetes mellitus and/ or chronic hypertension antedating the index pregnancy were removed and the perinatal outcome variables reanalyzed for this subset. Differences in demographic and perinatal variables were evaluated with a two-tailed Student t test, X2, and Fisher's exact test, where appropriate. The significance level was set at u = 0.05.
Results One hundred eleven massively obese pregnant women (weight >300 pounds during pregnancy) were identified during the study period among 25,636 consecutive deliveries (incidence 0.43%). One hundred eleven controls were selected as stated above. Data base
information and patient charts were available for all patients. Maternal descriptive variables are presented in Table 1. The mean maternal weight in the massively obese group was significantly greater than in the control group (p < 0.00001). By study design no significant differences were observed among the matched variables, age and parity, between the two groups. Although four sets of twins were delivered among the massively obese pregnant women, twinning was not observed in the control group (difference not statistically significant). Table II illustrates the occurrence of maternal medical complications of pregnancy between groups. The massively obese pregnant women were significantly more likely to be delivered by cesarean section (Table III). The overall cesarean section rate for the massively obese group was nearly double that of the control group (p = 0.0002). The primary cesarean section rate for massively obese pregnant women was also significantly increased (p = 0.002). No differences in the occurrence of placenta previa, abruptio placentae, or preterm delivery (delivery before 36 completed weeks gestation) were observed between groups. Table IV illustrates differences in neonatal outcome variables between groups. Neonates born to massively obese pregnant women were significantly more likely to exhibit both low birth weight (birth weight <2500 gm, p = 0.02) and macrosomia (birth weight >4000 gm, p = 0.0001). An increased frequency of intrauterine growth retardation (birth weight < 10th percentile for population) was also observed in the massively obese group (p = 0.03). Neonates born to massively obese pregnant women had I-minute Apgar scores more often <5 (p = 0.04); however, this difference did not
960
Perlow et al.
October 1992 Am J Obstet Gynecol
Table III. Perinatal outcome: Delivery variables Control (n = 111)
Obese Outcome
Cesarean section, overall Cesarean section, primary Cesarean section, cephalopelvic disproportion Cesearean section, fetal distress Delivery <36 wk
(n
= 111)
Odds ratio
95% Confidence interval
55.9 32.4 25.4
30.6 14.4 8.8
0.0003 0.003 0.12
2.9 2.9 3.3
1.6-5.2 1.4-5.9 0.8-14.6
22.0
17.6
0.90
1.2
0.4-4.2
13.5
8.1
0.28
1.8
0.7-4.6
Values expressed as percent.
Table IV. Perinatal outcome: Neonatal variables Outcome
Apgar score at 1 min <5 Apgar score at 5 min <7 Birth weight >4500 gm Birth weight >4000 gm Birth weight <2500 gm Intrauterine growth retardation Admitted to neonatal intensive care unit
p
Obese (n = 115)
Control (n = 111)
Value
Odds ratio
95% Confidence interval
13.0 7.8 13.0 30.4 14.7 7.8
4.5 2.7 1.8 10.8 4.5 0.9
0.04 0.16 0.003 0.0005 0.02 0.03
3.2 3.0 8.1 3.6 3.6 9.3
1.1-10.3 0.7-14.2 1.7-32.8 1.7-7.9 1.2-11.9 1.2-67.9
15.6
4.5
0.01
3.9
1.3-12.6
Values expressed as percent. For obese category n
=
115 because of four twin sets.
persist at 5 minutes. Interestingly, these neonates were also more likely to require admission to the neonatal intensive care unit (p = 0.01). To determine if significant differences in perinatal outcome were due to obesity per se or to medical complications more frequently observed in the massively obese group, the data were reanalyzed after excluding 29 massively obese patients with the diagnosis of chronic hypertension or insulin-requiring diabetes mellitus antedating pregnancy. The mean maternal age and parity for this group was again not significantly different from the control group (Table I). Mean maternal weight for this group was not significantly different from the overall massively obese group but was markedly different from controls (p < 0.0001). Without exception, no statistically significant differences in perinatal outcome were observed when the data were analyzed in this manner (Table V).
Comment The influence of obesity on the degradation of health is the subject of a wide body of literature. 13-2o Much is known regarding the obese individual's increased risk for coronary artery disease, diabetes mellitus, stroke, and cancer. However, much less is known regarding the impact of obesity on perinatal outcome. This study reports the perinatal outcome for a group of obese patients with a degree of obesity not previously reported in the literature. Our data analysis, with re-
spect to overall perinatal outcome and outcome between groups, excluding the obese patients with insulin-dependent diabetes mellitus or chronic hypertension, is also unique to the literature. We chose a pregnancy weight of >300 pounds to define massive obesity. This definition is random, because unfortunately a standardized nomenclature does not exist. However, obesity is commonly defined in terms of the body mass index (weight [kg]/height [m 2 ]) or percent ideal body weight (percent weight in relation to "ideal" weight determined from actuarial tables). \5 Obesity during pregnancy has been defined in a multitude of ways: as prepregnancy weight >200 pounds),'" > 120%8.10 or > 110% (mean obese weight 171 pounds), \I ideal body weight at first prenatal visit, gravid weight >90 kg,9 and body mass index >30. 13 Recently, Wolfe et al!1 reported no benefit in the use of maternal body mass index over the gravid weight in the risk assessment of outcomes related to maternal weight. Massive and morbid obesity have been defined as pregnancy weight >250 pounds,' prepregnancy weight 150% ideal body weight,"-Io morbid obesity as 200% ideal body weight, and grotesque obesity as three times "accepted desirable weight."6 This lack of uniformity makes interpreting the literature as a whole virtually impossible, emphasizing the importance of understanding the definitions used, populations studied, and outcome variables assessed in each study. We found a remarkable higher frequency of chronic
Massive obesity and perinatal outcome
Volume 167 Number 4, Part I
961
Table V. Perinatal outcome excluding massively obese with insulin-dependent diabetes mellitus and chronic hypertension Outcome
Cesarean section Primary cesarean section Apgar score at 1 min <5 Apgar score at 5 min <7 Birth weight >4500 gm Birth weight >4000 gm Birth weight <2500 gm Intrauterine growth retardation Admitted to neonatal intensive care unit
Obese (n = 82)
Control (n = 111)
42.7 19.5 4.9 2.4 3.7 14.6 3.7 4.9
30.6 14.4 4.5 2.7 1.8 11.7 4.5 0.9
4.9
1.9
Odds atio
95% Confidence interval
0.12 0.89 0.73 0.70 0.73 0.70 0.94 0.82
1.7 0.9 2.1 1.3 2.1 1.3 0.8 l.l
0.9-3.2 0.3-2.7 0.3-130.0 0.5-3.2 0.3-130.0 0.5-3.2 0.5-4.0 0.3-4.9
0.21
5.6
0.6-83.0
Values expressed as percent.
hypertension (27.0% vs 17.2%) and diabetes mellitus (19.8% vs 10.4%) in our massively obese group when compared with the morbidly obese group (> 150% ideal body weight) reported by Garbaciak et al.,10 although no differentiation was made between gestational and insulin-dependent diabetics. This observation may be related to the more obese population we studied, and these findings are consistent with the known increased association of these medical conditions with increasing "degrees" of obesity. 14·20. 22 In contrast to other studies demonstrating an increased risk of gestational diabetes,7. 12 we were unable to show such an association. Because these obese patients were multiparous and relatively older, it may be that they had previously been gestational diabetics and eventually were diagnosed as insulin-dependent by the time the index pregnancy occurred. This may also account for the high frequency of insulin-dependent diabetes observed in this group (Table II). In spite of a 27% frequency of chronic hypertension in our massively obese group, we were unable to demonstrate a statistically significant increased frequency of preeclampsia in this group. This is in contrast to previous observations!' 5. 7 However, a strong trend was present (p = 0.058), and with larger numbers significance might be met (Table II). We demonstrated significantly increased overall and primary cesarean section rates in the massively obese group (Table III). This is consistent with some9. 10. 12 but not alF- 9 reports. These differences were not observed to persist when the massively obese diabetics and hypertensives were removed from data analysis (Table V). This suggests that obesity per se does not lead to an increased risk of cesarean section but rather to the inherent increased risk of medical complications of pregnancy described. Garbaciak et al. 10 reported an increase in the primary cesarean section rate for morbidly obese patients after patients with antepartum complications were removed from data analysis. However, he re-
ported a frequency of chronic hypertension of 17.2% and of diabetes mellitus 10.4%. Removing fewer patients with these complications may not be expected to change the frequency of cesarean delivery. The finding of increased cesarean section rates for this population is particularly important when one considers the increased operative morbidity described for the obese patient population. 23 Before controlling for chronic hypertension and insulin-dependent diabetes mellitus, we found a significantly increased frequency of both low birth weight and macrosomic neonates in the massively obese group. Macrosomia is a rather consistent finding in pregnancy complicated by obesity" 5. 7·9. 12 and may be related to the increased frequency of diabetes (both gestational and insulin requiring) seen in this population. In contrast, patients with chronic hypertension and classes of diabetes associated with vasculopathy and nephropathy are at increased risk for low birth weight and intrauterine growth retardation. 24 • 25 The high frequency of chronic hypertension and insulin-dependent diabetes mellitus in our massively obese population could certainly account for these findings, because these differences were not apparent when these medical complications were controlled for (Table V). Our observation that neonates of the massively obese pregnant women were more frequently admitted to the neonatal intensive care unit is indicative of the high obstetric risk factors of chronic hypertension and insulin-dependent diabetes mellitus and not necessarily due to obesity in and of itself (Tables IV and V). Therefore it appears that pregnant women with a pregnancy weight> 300 pounds are at an increased risk for a multitude of adverse perinatal outcomes. Particularly striking is the enormously increased risk of chronic hypertension and diabetes mellitus in these patients, the higher rates of cesarean delivery and adverse neonatal outcomes, including low birth weight, intrauterine growth retardation, and admission to the neo-
962
Perlow et al.
natal intensive care unit. However, the present findings indicate that the massively obese pregnant women without chronic hypertension or insulin-dependent diabetes mellitus may experience normal perinatal outcome. These data may be useful in preconceptual and prenatal counseling and in the perinatal management of the massively obese pregnant woman. REFERENCES 1. Burton BT, Foster WR, Hirsch], Van Itallie TB. Health implications of obesity: an NIH consensus development conference. Int] Obesity 1985;9:155-69. 2. McDowell A, Engel A, Massey ]T, Maurer K. Plan and operation of the second National Health and Nutrition Examination Survey, 1976-1980. Hyattsville, Maryland: National Center for Health Statistics, 1981; DHHS publication no (PHS)81-1317. (Vital and health statistics; series I, no 15.) 3. National Center for Health Statistics. Anthropometric reference data and prevalence of overweight, United States, 1976-1980. Hyattsville, Maryland: National Center for Health Statistics, 1987; DHHS publication no (PHS)871688. (National Health Survey; series II, no 238.) 4. Odell LD, Mengert WF. The overweight obstetric patient. ]AMA 1945;128:87-90. 5. Tracy TA, Miller GL. Obstetric problems of the massively obese. Obstet Gynecol 1969;33:204-8. 6. Freedman MA, Preston LW, George WM. Grotesque obesity: a serious complication of labor and delivery. South Med] 1972;65:732-6. 7. Edwards LE, Dickes WF, Alton IR, Hadanson EY. Pregnancy in the massively obese: course, outcome and obesity prognosis of the infant. AM ] OBSTET GYNECOL 1978;131:479-83. 8. Harrison GG, Udall]N, Morrow III G. Maternal obesity weight gain in pregnancy, and infant birth weight. AM] OBSTET GYNECOL 1980;136:411-2. 9. Gross T, Sokol R], King K. Obesity in pregnancy: risks and outcome. Obstet Gynecol 1980;56:446-50. 10. Garbaciak]A]r, Richter M, Miller S, Barton]]. Maternal weight and pregnancy complications. AM] OBSTET GyNECOL 1985; 152:238-45. II. Mitchell MC, Lerner E. A comparison of pregnancy out-
October 1992 Am J Obstet Gynecol
12. 13. 14.
15.
16.
17. 18. 19. 20. 21. 22. 23. 24.
25.
come in overweight and normal weight women.] Am Coli Nutr 1989;8:617-24. Johnson SR, Kolberg BH, Varner MW, Railsback LD. Maternal obesity and pregnancy. Surg Gynecol Obstet 1987;164:431-7. Naeye RL. Maternal body weight and pregnancy outcome. Am] Clin Nutr 1990;52:273-9. Public Health Service. Healthy people 2000, national health promotion and disease prevention objectives. Washington: US Department of Health and Human Services, 1990; DHHS publication no (PHS)90-50212. Public Health Service. The Surgeon General's report on nutrition and health. Washington: US Department of Health and Human Services, 1988. DHHS publication no (PHS)88-5021O. Hubert HB, Feinleib M, McNamara PM, Castelli WP. Obesity as an independent risk factor for cardiovascular disease: a 26-year follow-up of participants in the Framingham Heart Study. Circulation 1983;67:968-77. Williamson DF, Kahn HS, Byers T. The 10-y incidence of obesity and major weight gain in black and white US women aged 30-55 y. Am] Clin Nutr 1991;53:1515-8S. Lew EA, Garfinkel L. Variations in mortality by weight among 750,000 men and women. ] Chronic Dis 1979;32:563-76. Garfinkel L. Overweight and cancer. Ann Intern Med 1985; 103: 1034-6. Kral ]G. Morbid obesity and related health risks. Ann Intern Med 1985;103:1043-7. Wolfe HM, Zador IE, Gross TL, Martier SS, Sokol RJ. The clinical utility of maternal body mass index in pregnancy. AM] OBSTET GYNECOL 1991;164:1306-10. Bray GA. Complications of obesity. Ann Intern Med 1985;104: 1052-62. Wolfe HM, Gross TL, Sokol R], Bottoms SF, Thompson KL. Determinants of morbidity in obese women delivered by cesarean. Obstet Gynecol 1988;71:691-6. Main DM, Main EK. Preterm birth. In: Gabbe SG, Niebyl ]R, Simpson ]L, eds. Obstetrics: normal and problem pregnancies. ed 2. New York: Churchill Livingstone, 1991:838. Gabbe SG. Intrauterine growth retardation. In: Gabbe SG, Niebyl ]R, Simpson ]L, eds. Obstetrics: normal and problem pregnancies. ed 2. New York: Churchill Livingstone, 1991 :926.