Previous cesarean delivery and risks of placenta previa and placental abruption.
OBJECTIVE
To examine the association between cesarean delivery and previa and abruption in subsequent pregnancies.


METHODS
A retrospective cohort study of first 2 (n = 156,475) and first 3 (n = 31,102) consecutive singleton pregnancies using the 1989-1997 Missouri longitudinally linked data were performed. Relative risk (RR) was used to quantify the associations between cesarean delivery and risks of previa and abruption in subsequent pregnancies, after adjusting for several confounders.


RESULTS
Rates of previa and abruption were 4.4 (n = 694) and 7.9 (n = 1,243) per 1,000 births, respectively. The pregnancy after a cesarean delivery was associated with increased risk of previa (0.63%) compared with a vaginal delivery (0.38%, RR 1.5, 95% confidence interval [CI] 1.3-1.8). Cesarean delivery in the first and second births conferred a two-fold increased risk of previa in the third pregnancy (RR 2.0, 95% CI 1.3-3.0) compared with first two vaginal deliveries. Women with a cesarean first birth were more likely to have an abruption in the second pregnancy (0.95%) compared with women who had a vaginal first birth (0.74%, RR 1.3, 95% CI 1.2-1.5). Two consecutive cesarean deliveries were associated with a 30% increased risk of abruption in the third pregnancy (RR 1.3, 95% CI 1.0-1.8). A second pregnancy within a year after a cesarean delivery was associated with increased risks of previa (RR 1.7, 95% CI 0.9-3.1) and abruption (RR 1.5, 95% CI 1.1-2.3).


CONCLUSIONS
A cesarean first birth is associated with increased risks of previa and abruption in the second pregnancy. There is a dose-response pattern in the risk of previa, with increasing number of prior cesarean deliveries. A short interpregnancy interval is associated with increased risks of previa and abruption.


METHODS
II-2.
Division of Epidemiology and Biostatistics, Department of Obstetrics, Gynecology, and Reproductive Sciences, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick 08901-1977, USA.
Darios
D
Getahun
Yinka
Y
Oyelese
Hamisu M
HM
Salihu
Cande V
CV
Ananth
D000037:Abruptio Placentae / Q000175:diagnosis / Q000453:epidemiology*; D000328:Adult; D017677:Age Distribution; D002585:Cesarean Section / Q000009:adverse effects* / Q000379:methods; D017604:Cesarean Section, Repeat / Q000009:adverse effects / Q000379:methods; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D009321:Natural Childbirth / Q000009:adverse effects / Q000379:methods*; D010298:Parity; D010923:Placenta Previa / Q000175:diagnosis / Q000453:epidemiology*; D011247:Pregnancy; D015995:Prevalence; D011336:Probability; D012189:Retrospective Studies; D018570:Risk Assessment