- Email: [email protected]
586: Risk profiles for normotensive and hypertensive small for gestational age (SGA) infants include different clinical and ultrasound indices - data from the SCOPE study
www.AJOG.org
Epidemiology, Global Maternal-Fetal Public Health, Infectious Disease, Intrapartum Fetal Assessment, Operative Obstetrics
Poster Session IV
CONCLUSIONS: LPI rates have risen for all gravid women in the US, and in particular for those without recorded antenatal risk factors. These results suggest that there may be an increasingly lower threshold to initiate labor by induction and that future study should focus on the reasons underlying this trend.
583 Do differences in Down syndrome livebirth rates by maternal education persist after controlling for maternal age? Kari Horowitz1, James Egan1, Alireza Shamshirsaz1, Winston Campbell1, Peter Benn1 1
University of Connecticut Health Center, Farmington, CT
OBJECTIVE: Differences in demographic attitudes toward Down syn-
drome (DS) screening have been reported. Women with more years of education are generally older at the time of childbirth, and older women are at greater risk for having a DS child. We therefore sought to determine if there were differences in rates of DS livebirths related to maternal education (EDU) in the US after adjustment for maternal age. STUDY DESIGN: Using Data from the National Center for Health Statistics from 1990 to 2006, the number of reported maternal age-specific DS livebirths was stratified by maternal age. Data was collected by the level of EDU, ie ⱕ12 years or ⱖ13 years. We assumed no difference in the accuracy of birth certificate reporting of DS for the two groups. Data was then standardized for maternal age by multipling the total number of reported DS livebirths to women with ⱖ13 years EDU by the overall rate of DS for each year of maternal age. The rates of reported DS livebirths by EDU group were compared using the MantelHaenszel test; a p ⬍ 0.05 considered significant. RESULTS: There were a total of 34,740,236 livebirths to women with ⱕ12 years EDU and 27,822,822 livebirths to women with ⱖ13 years EDU from 1990 to 2006. During this period there were 13,543 DS livebirths to women with ⱖ13 years EDU which is less than the agestandardized number of 14,700 DS livebirths expected during this period (p⬍0.001). CONCLUSIONS: After age standardization, the reported number of DS livebirths was significantly lower than expected in the ⱖ13 years EDU group from 1990-2006. This shows that the difference in DS livebirths by EDU persists after controlling for maternal age, possibily reflecting greater use of prenatal screening and diagnosis together with higher rates of termination of affected pregnancies.
584 National trends in induction of labor at late preterm gestations Karna Murthy1, William A. Grobman2, Jane Holl2 1 Northwestern University, Chicago, IL, 2Northwestern University Feinberg School of Medicine, Chicago, IL
OBJECTIVE: To determine the longitudinal trends in late preterm induction (LPI) in the United States (US). STUDY DESIGN: Data from the National Center for Health Statistics were used to identify women eligible for induction who delivered between 340/7 - 426/7 weeks’ gestation in the US from 1991-2006. Annual LPI rates were calculated as the number of women induced between 340/7 and 366/7 weeks’ gestation as a proportion of infants born between 34-42 weeks’ gestation. Denominators were adjusted to account for advancing gestational age. Women with prior cesarean deliveries, fetal anomalies, unknown gestational age or labor initiation, or inadequate prenatal care were excluded. Descriptive trends are presented, and also, multivariable logistic regression was used to estimate the change in odds of LPI for all eligible women and for women after stratification by the presence of diabetes (DM) and chronic hypertension (CHTN). RESULTS: 48.6 million women were eligible for the study. LPI rates increased from 0.65% to 1.59% (p⬍0.01). Among women with DM or CHTN, annual LPI rates were significantly higher, however, these rates increased at a similar rate (DM: 1.42% to 2.24%; CHTN: 3.14% to 5.03%, p⬍0.001). After adjusting for confounding, the increase in the odds of LPI was significantly less for women with DM or CHTN compared with women without either of these recorded conditions (DM: 98%, CHTN 70%, 193% increase without any risk factors, p⬍0.01 for change over time).
585 Racial/ethnic differences in labor induction at early-term gestations Karna Murthy1, William A. Grobman2, Todd Lee3, Jane Holl2 1 Northwestern University, Chicago, IL, 2Northwestern University Feinberg School of Medicine, Chicago, IL, 3 University of Illinois at Chicago, Chicago, IL
OBJECTIVE: To determine the longitudinal trends and racial differences in early-term induction (ETI) in the United States (US). STUDY DESIGN: Data from the National Center for Health Statistics were used to identify women eligible for induction between 37-42 weeks’ gestation in the US from 1991-2006. Annual ETI rates were calculated as the number of women induced between 370/7 ⫺386/7 weeks’ gestation as a proportion of infants born between 37-42 weeks. The denominator was adjusted to account for advancing gestational age. Race/ethnicity was categorized into 4 groups: non-Hispanic white (NHW), Hispanic white (HW), black (B), and other (O). Women with prior cesarean deliveries, fetal anomalies, inadequate prenatal care, or unknown gestational age or labor initiation were excluded. Descriptive trends were calculated, stratified by the presence of diabetes (DM) or chronic hypertension (CHTN) and multivariable logistic regression was used to estimate the change in odds of ETI by race/ethnicity over time. RESULTS: For 43.5 million eligible women, ETI rates increased from 2.4% to 8.8% (p⬍0.01). ETI was highest and rose most among NHW women (2.7% to 10.4%) although all four groups exhibited a significant increase in ETI (HW: 1.5% to 5.9%; B: 2.2% to 8.6%; O: 1.8% to 6.0%; p ⬍ 0.01 for 4 groups). For women with DM or CHTN, ETI rates were higher and rose during the study period, (8.8% to 17.9% for DM; 13.1% to 26.9% for CHTN), although the rise was less than for women without either risk factor (DM or CHTN: mean of ⫹6.5% change/yr; neither: mean of ⫹9.6% change/yr, p⬍0.01). For women without risk factors and after adjustment for age, parity, and marital status, the adjusted odds of ETI was highest (p⬍0.01) and rose the most rapidly (p⬍0.01) among NHW women (21%/yr) compared with women from all other racial/ethnic groups (B 20%/yr; HW 19%/ yr and O 16%/yr, p⬍0.01 over time). CONCLUSIONS: ETI increased more than 3-fold for all gravid women in the US although this rise has been disproportionately higher among NHW women without recorded antenatal risk factors.
586 Risk profiles for normotensive and hypertensive small for gestational age (SGA) infants include different clinical and ultrasound indices - data from the SCOPE study Lesley McCowan1, Robyn North2, Eliza Chan1, Rennae Taylor1, Lucy Chappell3, Jenny Myers4, Louise Kenny5, Gustaaf Dekker6 1
University of Auckland, Auckland, 2Kings College, London, Auckland, King’s College London, London, 4University of Manchester, Manchester, 5 Anu Research Centre, Department of Obstetrics and Gynaecology, University College Cork, Cork, 6University of Adelaide, Adelaide 3
OBJECTIVE: Less than 40% of SGA infants are recognized before birth and about half of stillbirths are SGA. Better detection may lower morbidity and mortality. SGA infants can be divided into 2 broad groups: those with normotensive mothers (NT-SGA) and hypertensive mothers (HT-SGA). We aimed to build risk prediction models for NT-SGA and HT-SGA using clinical and ultrasound data. STUDY DESIGN: Healthy nullipara recruited to the SCOPE study in New Zealand, Australia, the United Kingdom and Ireland participated. Detailed clinical data were collected at 15⫾1 weeks (n⫽3513) and fetal measurements, umbilical and uterine artery Doppler indices were recorded at the 20 week scan (n⫽3347). The primary outcomes were NT-SGA and HT-SGA defined as birthweight ⬍10th customized
Supplement to JANUARY 2011 American Journal of Obstetrics & Gynecology
S233
Poster Session IV
Epidemiology, Global Maternal-Fetal Public Health, Infectious Disease, Intrapartum Fetal Assessment, Operative Obstetrics
centile with a normotensive or hypertensive mother, respectively. Candidate clinical risk factors, fetal growth measurements, uterine and umbilical Doppler indices were analyzed by stepwise logistic regression. ROC curves and test characteristics were generated. RESULTS: Among 376 (10.7%) SGA infants, 281 (74.7%) were NTSGA and 95 (25.3%) HT-SGA. Independent risk factors for NT-SGA included: mother born SGA, smoking, extreme exercise, smaller fetal size and higher uterine Doppler resistance index (RI) at the 20 week scan, whereas leafy vegetables, and Rhesus negative blood group were protective. The area under the ROC curve was 0.74, sensitivity 58%, specificity 75%, PPV 16% and NPV 96%. Risk factors for HT-SGA included higher diastolic BP and BMI, fertility treatment, history of hypertension on the combined oral contraceptive, higher uterine and umbilical artery RI and smaller fetal size on the 20 week scan. The area under the ROC curve was 0.80, sensitivity 72%, specificity 75%, PPV 8% and NPV 99%. CONCLUSIONS: Modest risk prediction was achieved for NT-SGA and HT-SGA infants using clinical and ultrasound data from the first 20 weeks of pregnancy. These models require validation in other cohorts of nullipara. Future studies will determine whether performance is improved by addition of biomarker data.
587 Trending elective preterm deliveries using administrative data Lisa M. Korst1, Moshe Fridman2, Michael C. Lu1, Connie Mitchell3, Kimberly D. Gregory4 1 University of California, Los Angeles, CA, 2AMF Consulting, Inc., Los Angeles, CA, 3California Department of Public Health, Sacramento, CA, 4Cedars-Sinai Health Systems, Los Angeles, CA
OBJECTIVE: Using administrative data, we developed a methodology to distinguish “indicated” and spontaneous preterm births from “elective” preterm births, and examined the trend in preterm birth rates from 1999-2005 in California. STUDY DESIGN: Data were obtained from the California linked birth cohort data for 1999, 2002 and 2005. Preterm birth was identified from birth certificate gestational age ⱖ⫽ 20 and ⫽ⱕ37 weeks. All preterm births were classified into one of 3 groups: (1) “Complicated” preterm deliveries with specified medical/obstetrical pregnancy complications; (2) “Elective” preterm deliveries without medical/obstetrical complications but with coding of an elective cesarean or induction of labor; and (3) “Spontaneous” preterm deliveries (remaining preterm births). Rates of preterm deliveries were calculated by study year and, using hierarchical logistic regression models, were adjusted for multiple maternal and hospital-level variables. Median maternal and newborn hospital charges were also trended. Linear trends were evaluated for 3 and 6 year periods. RESULTS: Preterm births increased from 5.5% of all deliveries in 1999 to 6.1% in 2005, representing a 20.6% increase over the study period (P⬍0.0001). Complicated preterm deliveries increased from 20.8% to 22.5%; Elective preterm deliveries increased from 15.3% to 20.7%; and Spontaneous preterm deliveries decreased from 63.9% to 56.8%. For each group, maternal and neonatal median charges increased over the study period, and maternal median charges exceeded neonatal charges. The median charges associated with the Elective preterm delivery group exceeded charges for the Spontaneous labor group. CONCLUSIONS: Overall, preterm births increased 21% from 19992005. Much of this increase appears associated with elective deliveries prior to 37 weeks, and in 2005, these elective deliveries accounted for one in five preterm births. Hospital charges for this group exceeded charges for spontaneous preterm births. Such findings are of public health concern and require validation from clinical data sources.
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588 Late preterm birth and cesarean delivery in a population-dased study Margaret Carter1, Sharon Fowler1, Alan Holden1, Beth Thai1, Donald Dudley1 1
University of Texas Health Science Center at San Antonio, San Antonio, TX
OBJECTIVE: The aim of the study was to evaluate the associations be-
tween late preterm birth (LPB) and cesarean delivery (CD). STUDY DESIGN: A retrospective cross-sectional analysis was conducted using de-identified delivery data obtained from the San Antonio Metropolitan Health District for all (n ⫽259,576) who delivered in San Antonio/Bexar County (SA/BC) from 2000-2008. LPB was defined as a live birth at 340/7-366/7 weeks. Variables studied were age, race/ethnicity, weight gain, hypertensive disease (HD), diabetes (DM), and preterm labor including premature rupture of membranes (PTL/ PPROM). Statistical analysis was done using Chi-square and logistic regression. RESULTS: The LPB rate in SA/BC during the study period was 9%; 3.1% were delivered by CD (LPBCD). CD itself was associated with an increased risk of LPB (relative risk, 1.58; [95% CI, 1.54-1.62]). All study variables were associated with an increased LPBCD risk except for black race (0.76; [0.66-0.88]), Hispanic ethnicity (0.87; [0.840.91]), and age⬍17 (0.68; [0.58-0.8]) which were associated with a decreased risk; and other race and PTL/PPROM which were not significant. Using logistic regression (LPBCD vs. LPB by vaginal delivery), the following variables continued to be associated with an increased LPBCD risk: ageⱖ35 (odds ratio, 1.86; [1.70 to 2.04]), white race (1.77; [1.42-2.22]), gestational weight gain ⬎45lbs (2.41; [2.2-2.64]), gestational hypertension (3.0; [2.68-3.35]), eclampsia (1.79; [1.25-2.55]), chronic hypertension (2.97; [2.34-3.76]), and DM (1.74; [1.5-2.01]). Black race (0.64; [0.47-0.87]) and age⬍17 (0.54; [0.44-0.67]) continued to be associated witha decreased risk. Hispanic ethnicity and PTL/ PPROM were not significant. CONCLUSIONS: As expected, LPBCD risk increased with advanced maternal age, excessive gestational weight gain, HD, and DM. Surprisingly, black race and age⬍17 were associated with decreased risk and white race with increased risk. The latter findings may reflect physician/hospital management styles rather than pathophysiology.
589 The risk of perinatal death stratified by gestational age: a novel methodologic approach Melissa G. Rosenstein1, James Nicholson2, Yvonne W. Cheng1, Clara Ward1, Aaron B. Caughey3 1
University of California, San Francisco, San Francisco, CA, University of Pennsylania, Philadelphia, PA, 3Oregon Health & Science University, Portland, OR
2
OBJECTIVE: To develop a methodology to examine and compare risk of perinatal mortality stratified by gestational age. STUDY DESIGN: This is a retrospective cohort study that included all deliveries in the state of California from 1997-2006. Infant mortality rates at each gestational age (GA) were calculated. Intrauterine fetal demise (IUFD) rate at each GA was calculated using a denominator of 10,000 ongoing pregnancies. A novel composite mortality rate was developed to calculate perinatal risk of expectant management at each gestational age incorporating the IUFD risk during the week of continuing pregnancy plus the infant mortality risk at the gestational age one week hence. RESULTS: The risk of IUFD at term increases with gestational age. Infant mortality rates have a “U” shaped pattern, highest at 37 weeks with a nadir at 39 weeks. The composite risk of expectant management best replicates the risk faced by a pregnant woman and her clinician in determining the mortality risk of delivery (infant death rate) compared with expectant management (IUFD risk this week ⫹ infant death rate next week). At 38 weeks the risk expectant management carries the same risk of perinatal death as delivery, but at each later gestational age, the perinatal death risk of expectant management is higher (p⬍0.001).
American Journal of Obstetrics & Gynecology Supplement to JANUARY 2011
Epidemiology, Global Maternal-Fetal Public Health, Infectious Disease, Intrapartum Fetal Assessment, Operative Obstetrics
Poster Session IV
CONCLUSIONS: LPI rates have risen for all gravid women in the US, and in particular for those without recorded antenatal risk factors. These results suggest that there may be an increasingly lower threshold to initiate labor by induction and that future study should focus on the reasons underlying this trend.
583 Do differences in Down syndrome livebirth rates by maternal education persist after controlling for maternal age? Kari Horowitz1, James Egan1, Alireza Shamshirsaz1, Winston Campbell1, Peter Benn1 1
University of Connecticut Health Center, Farmington, CT
OBJECTIVE: Differences in demographic attitudes toward Down syn-
drome (DS) screening have been reported. Women with more years of education are generally older at the time of childbirth, and older women are at greater risk for having a DS child. We therefore sought to determine if there were differences in rates of DS livebirths related to maternal education (EDU) in the US after adjustment for maternal age. STUDY DESIGN: Using Data from the National Center for Health Statistics from 1990 to 2006, the number of reported maternal age-specific DS livebirths was stratified by maternal age. Data was collected by the level of EDU, ie ⱕ12 years or ⱖ13 years. We assumed no difference in the accuracy of birth certificate reporting of DS for the two groups. Data was then standardized for maternal age by multipling the total number of reported DS livebirths to women with ⱖ13 years EDU by the overall rate of DS for each year of maternal age. The rates of reported DS livebirths by EDU group were compared using the MantelHaenszel test; a p ⬍ 0.05 considered significant. RESULTS: There were a total of 34,740,236 livebirths to women with ⱕ12 years EDU and 27,822,822 livebirths to women with ⱖ13 years EDU from 1990 to 2006. During this period there were 13,543 DS livebirths to women with ⱖ13 years EDU which is less than the agestandardized number of 14,700 DS livebirths expected during this period (p⬍0.001). CONCLUSIONS: After age standardization, the reported number of DS livebirths was significantly lower than expected in the ⱖ13 years EDU group from 1990-2006. This shows that the difference in DS livebirths by EDU persists after controlling for maternal age, possibily reflecting greater use of prenatal screening and diagnosis together with higher rates of termination of affected pregnancies.
584 National trends in induction of labor at late preterm gestations Karna Murthy1, William A. Grobman2, Jane Holl2 1 Northwestern University, Chicago, IL, 2Northwestern University Feinberg School of Medicine, Chicago, IL
OBJECTIVE: To determine the longitudinal trends in late preterm induction (LPI) in the United States (US). STUDY DESIGN: Data from the National Center for Health Statistics were used to identify women eligible for induction who delivered between 340/7 - 426/7 weeks’ gestation in the US from 1991-2006. Annual LPI rates were calculated as the number of women induced between 340/7 and 366/7 weeks’ gestation as a proportion of infants born between 34-42 weeks’ gestation. Denominators were adjusted to account for advancing gestational age. Women with prior cesarean deliveries, fetal anomalies, unknown gestational age or labor initiation, or inadequate prenatal care were excluded. Descriptive trends are presented, and also, multivariable logistic regression was used to estimate the change in odds of LPI for all eligible women and for women after stratification by the presence of diabetes (DM) and chronic hypertension (CHTN). RESULTS: 48.6 million women were eligible for the study. LPI rates increased from 0.65% to 1.59% (p⬍0.01). Among women with DM or CHTN, annual LPI rates were significantly higher, however, these rates increased at a similar rate (DM: 1.42% to 2.24%; CHTN: 3.14% to 5.03%, p⬍0.001). After adjusting for confounding, the increase in the odds of LPI was significantly less for women with DM or CHTN compared with women without either of these recorded conditions (DM: 98%, CHTN 70%, 193% increase without any risk factors, p⬍0.01 for change over time).
585 Racial/ethnic differences in labor induction at early-term gestations Karna Murthy1, William A. Grobman2, Todd Lee3, Jane Holl2 1 Northwestern University, Chicago, IL, 2Northwestern University Feinberg School of Medicine, Chicago, IL, 3 University of Illinois at Chicago, Chicago, IL
OBJECTIVE: To determine the longitudinal trends and racial differences in early-term induction (ETI) in the United States (US). STUDY DESIGN: Data from the National Center for Health Statistics were used to identify women eligible for induction between 37-42 weeks’ gestation in the US from 1991-2006. Annual ETI rates were calculated as the number of women induced between 370/7 ⫺386/7 weeks’ gestation as a proportion of infants born between 37-42 weeks. The denominator was adjusted to account for advancing gestational age. Race/ethnicity was categorized into 4 groups: non-Hispanic white (NHW), Hispanic white (HW), black (B), and other (O). Women with prior cesarean deliveries, fetal anomalies, inadequate prenatal care, or unknown gestational age or labor initiation were excluded. Descriptive trends were calculated, stratified by the presence of diabetes (DM) or chronic hypertension (CHTN) and multivariable logistic regression was used to estimate the change in odds of ETI by race/ethnicity over time. RESULTS: For 43.5 million eligible women, ETI rates increased from 2.4% to 8.8% (p⬍0.01). ETI was highest and rose most among NHW women (2.7% to 10.4%) although all four groups exhibited a significant increase in ETI (HW: 1.5% to 5.9%; B: 2.2% to 8.6%; O: 1.8% to 6.0%; p ⬍ 0.01 for 4 groups). For women with DM or CHTN, ETI rates were higher and rose during the study period, (8.8% to 17.9% for DM; 13.1% to 26.9% for CHTN), although the rise was less than for women without either risk factor (DM or CHTN: mean of ⫹6.5% change/yr; neither: mean of ⫹9.6% change/yr, p⬍0.01). For women without risk factors and after adjustment for age, parity, and marital status, the adjusted odds of ETI was highest (p⬍0.01) and rose the most rapidly (p⬍0.01) among NHW women (21%/yr) compared with women from all other racial/ethnic groups (B 20%/yr; HW 19%/ yr and O 16%/yr, p⬍0.01 over time). CONCLUSIONS: ETI increased more than 3-fold for all gravid women in the US although this rise has been disproportionately higher among NHW women without recorded antenatal risk factors.
586 Risk profiles for normotensive and hypertensive small for gestational age (SGA) infants include different clinical and ultrasound indices - data from the SCOPE study Lesley McCowan1, Robyn North2, Eliza Chan1, Rennae Taylor1, Lucy Chappell3, Jenny Myers4, Louise Kenny5, Gustaaf Dekker6 1
University of Auckland, Auckland, 2Kings College, London, Auckland, King’s College London, London, 4University of Manchester, Manchester, 5 Anu Research Centre, Department of Obstetrics and Gynaecology, University College Cork, Cork, 6University of Adelaide, Adelaide 3
OBJECTIVE: Less than 40% of SGA infants are recognized before birth and about half of stillbirths are SGA. Better detection may lower morbidity and mortality. SGA infants can be divided into 2 broad groups: those with normotensive mothers (NT-SGA) and hypertensive mothers (HT-SGA). We aimed to build risk prediction models for NT-SGA and HT-SGA using clinical and ultrasound data. STUDY DESIGN: Healthy nullipara recruited to the SCOPE study in New Zealand, Australia, the United Kingdom and Ireland participated. Detailed clinical data were collected at 15⫾1 weeks (n⫽3513) and fetal measurements, umbilical and uterine artery Doppler indices were recorded at the 20 week scan (n⫽3347). The primary outcomes were NT-SGA and HT-SGA defined as birthweight ⬍10th customized
Supplement to JANUARY 2011 American Journal of Obstetrics & Gynecology
S233
Poster Session IV
Epidemiology, Global Maternal-Fetal Public Health, Infectious Disease, Intrapartum Fetal Assessment, Operative Obstetrics
centile with a normotensive or hypertensive mother, respectively. Candidate clinical risk factors, fetal growth measurements, uterine and umbilical Doppler indices were analyzed by stepwise logistic regression. ROC curves and test characteristics were generated. RESULTS: Among 376 (10.7%) SGA infants, 281 (74.7%) were NTSGA and 95 (25.3%) HT-SGA. Independent risk factors for NT-SGA included: mother born SGA, smoking, extreme exercise, smaller fetal size and higher uterine Doppler resistance index (RI) at the 20 week scan, whereas leafy vegetables, and Rhesus negative blood group were protective. The area under the ROC curve was 0.74, sensitivity 58%, specificity 75%, PPV 16% and NPV 96%. Risk factors for HT-SGA included higher diastolic BP and BMI, fertility treatment, history of hypertension on the combined oral contraceptive, higher uterine and umbilical artery RI and smaller fetal size on the 20 week scan. The area under the ROC curve was 0.80, sensitivity 72%, specificity 75%, PPV 8% and NPV 99%. CONCLUSIONS: Modest risk prediction was achieved for NT-SGA and HT-SGA infants using clinical and ultrasound data from the first 20 weeks of pregnancy. These models require validation in other cohorts of nullipara. Future studies will determine whether performance is improved by addition of biomarker data.
587 Trending elective preterm deliveries using administrative data Lisa M. Korst1, Moshe Fridman2, Michael C. Lu1, Connie Mitchell3, Kimberly D. Gregory4 1 University of California, Los Angeles, CA, 2AMF Consulting, Inc., Los Angeles, CA, 3California Department of Public Health, Sacramento, CA, 4Cedars-Sinai Health Systems, Los Angeles, CA
OBJECTIVE: Using administrative data, we developed a methodology to distinguish “indicated” and spontaneous preterm births from “elective” preterm births, and examined the trend in preterm birth rates from 1999-2005 in California. STUDY DESIGN: Data were obtained from the California linked birth cohort data for 1999, 2002 and 2005. Preterm birth was identified from birth certificate gestational age ⱖ⫽ 20 and ⫽ⱕ37 weeks. All preterm births were classified into one of 3 groups: (1) “Complicated” preterm deliveries with specified medical/obstetrical pregnancy complications; (2) “Elective” preterm deliveries without medical/obstetrical complications but with coding of an elective cesarean or induction of labor; and (3) “Spontaneous” preterm deliveries (remaining preterm births). Rates of preterm deliveries were calculated by study year and, using hierarchical logistic regression models, were adjusted for multiple maternal and hospital-level variables. Median maternal and newborn hospital charges were also trended. Linear trends were evaluated for 3 and 6 year periods. RESULTS: Preterm births increased from 5.5% of all deliveries in 1999 to 6.1% in 2005, representing a 20.6% increase over the study period (P⬍0.0001). Complicated preterm deliveries increased from 20.8% to 22.5%; Elective preterm deliveries increased from 15.3% to 20.7%; and Spontaneous preterm deliveries decreased from 63.9% to 56.8%. For each group, maternal and neonatal median charges increased over the study period, and maternal median charges exceeded neonatal charges. The median charges associated with the Elective preterm delivery group exceeded charges for the Spontaneous labor group. CONCLUSIONS: Overall, preterm births increased 21% from 19992005. Much of this increase appears associated with elective deliveries prior to 37 weeks, and in 2005, these elective deliveries accounted for one in five preterm births. Hospital charges for this group exceeded charges for spontaneous preterm births. Such findings are of public health concern and require validation from clinical data sources.
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588 Late preterm birth and cesarean delivery in a population-dased study Margaret Carter1, Sharon Fowler1, Alan Holden1, Beth Thai1, Donald Dudley1 1
University of Texas Health Science Center at San Antonio, San Antonio, TX
OBJECTIVE: The aim of the study was to evaluate the associations be-
tween late preterm birth (LPB) and cesarean delivery (CD). STUDY DESIGN: A retrospective cross-sectional analysis was conducted using de-identified delivery data obtained from the San Antonio Metropolitan Health District for all (n ⫽259,576) who delivered in San Antonio/Bexar County (SA/BC) from 2000-2008. LPB was defined as a live birth at 340/7-366/7 weeks. Variables studied were age, race/ethnicity, weight gain, hypertensive disease (HD), diabetes (DM), and preterm labor including premature rupture of membranes (PTL/ PPROM). Statistical analysis was done using Chi-square and logistic regression. RESULTS: The LPB rate in SA/BC during the study period was 9%; 3.1% were delivered by CD (LPBCD). CD itself was associated with an increased risk of LPB (relative risk, 1.58; [95% CI, 1.54-1.62]). All study variables were associated with an increased LPBCD risk except for black race (0.76; [0.66-0.88]), Hispanic ethnicity (0.87; [0.840.91]), and age⬍17 (0.68; [0.58-0.8]) which were associated with a decreased risk; and other race and PTL/PPROM which were not significant. Using logistic regression (LPBCD vs. LPB by vaginal delivery), the following variables continued to be associated with an increased LPBCD risk: ageⱖ35 (odds ratio, 1.86; [1.70 to 2.04]), white race (1.77; [1.42-2.22]), gestational weight gain ⬎45lbs (2.41; [2.2-2.64]), gestational hypertension (3.0; [2.68-3.35]), eclampsia (1.79; [1.25-2.55]), chronic hypertension (2.97; [2.34-3.76]), and DM (1.74; [1.5-2.01]). Black race (0.64; [0.47-0.87]) and age⬍17 (0.54; [0.44-0.67]) continued to be associated witha decreased risk. Hispanic ethnicity and PTL/ PPROM were not significant. CONCLUSIONS: As expected, LPBCD risk increased with advanced maternal age, excessive gestational weight gain, HD, and DM. Surprisingly, black race and age⬍17 were associated with decreased risk and white race with increased risk. The latter findings may reflect physician/hospital management styles rather than pathophysiology.
589 The risk of perinatal death stratified by gestational age: a novel methodologic approach Melissa G. Rosenstein1, James Nicholson2, Yvonne W. Cheng1, Clara Ward1, Aaron B. Caughey3 1
University of California, San Francisco, San Francisco, CA, University of Pennsylania, Philadelphia, PA, 3Oregon Health & Science University, Portland, OR
2
OBJECTIVE: To develop a methodology to examine and compare risk of perinatal mortality stratified by gestational age. STUDY DESIGN: This is a retrospective cohort study that included all deliveries in the state of California from 1997-2006. Infant mortality rates at each gestational age (GA) were calculated. Intrauterine fetal demise (IUFD) rate at each GA was calculated using a denominator of 10,000 ongoing pregnancies. A novel composite mortality rate was developed to calculate perinatal risk of expectant management at each gestational age incorporating the IUFD risk during the week of continuing pregnancy plus the infant mortality risk at the gestational age one week hence. RESULTS: The risk of IUFD at term increases with gestational age. Infant mortality rates have a “U” shaped pattern, highest at 37 weeks with a nadir at 39 weeks. The composite risk of expectant management best replicates the risk faced by a pregnant woman and her clinician in determining the mortality risk of delivery (infant death rate) compared with expectant management (IUFD risk this week ⫹ infant death rate next week). At 38 weeks the risk expectant management carries the same risk of perinatal death as delivery, but at each later gestational age, the perinatal death risk of expectant management is higher (p⬍0.001).
American Journal of Obstetrics & Gynecology Supplement to JANUARY 2011