Previous c-section linked with increased risk of stillbirth
Add this to another reason to try to limit
unnecessary primary c-sections--apparently, a previous
c-section increases the risk of stillbirth in
subsequent pregnancies. Fortunately, while the
increase is statistically significant, it is not huge
(this study found an increase from 0.5 per 1000 to
1.1 per 1000 for unexplained stillbirth at or after
39 weeks), so the odds are still overwhelmingly in
favor of a healthy baby. Still, something that should
be considered when weighing either elective c-section
or interventions that increase the risk of c-section.
Obstet Gynecol Surv. 2004 Jun;59(6):413-5.
Cesarean section and risk of unexplained stillbirth in
Smith GC, Pell JP, Dobbie R.
Department of Obstetrics and Gynaecology, Cambridge University,
Cambridge, U.K.; the Department of Public Health, Greater
Glasgow NHS Board, Glasgow, U.K.; and the Information and
Statistics Division, Common Services Agency, Edinburgh, U.K.
Apart from the risk of uterine rupture at vaginal delivery after a
previous cesarean birth, placental complications, including abruption
and placenta previa, reportedly are more common in these women. This
large-scale retrospective cohort study sought to determine whether
cesarean delivery of a first infant correlates with a higher risk of
antepartum stillbirth in the second pregnancy. The study population
included all second births in Scotland in the years 1992-1998. In
surveying 120,633 singleton second births, there were 68 antepartum
stillbirths among 17,754 women who previously had a cesarean delivery.
The incidence was 2.39 per 10,000 women per week. In 102,879 women who
previously delivered vaginally, the corresponding figure was 1.44. The
excessive risk of unexplained stillbirth in women with a previous
cesarean delivery was apparent from 34 weeks gestational age (hazard
ratio, 2.23; 95% confidence interval [CI], 1.48-3.36). Controlling for
maternal characteristics and the outcome of first pregnancies did not
substantially alter the risk (hazard ratio, 2.74; 95% CI, 1.74-4.30).
The absolute risk of unexplained stillbirth at or after 39 weeks
gestation was 1.1 per 1000 women having a previous cesarean delivery and
0.5 per 1000 in those who had not. The chief determinant of the excess
of stillbirths in women with a previous cesarean delivery was
unexplained stillbirth. The increased risk was not limited to deliveries
at or after 41 weeks gestation. The findings were unchanged when only
women delivering at term in their first pregnancy were analyzed. For
unexplained stillbirths at or after 34 weeks gestation, median birth
weight in women having a previous cesarean delivery was less than in
those whose first deliveries were vaginal. These associations were
confirmed on multivariate analysis. Women having cesarean delivery are
more likely than those delivering vaginally to have an antepartum
stillbirth in their second pregnancy. The major reason is an excess of
unexplained stillbirths. Possibly ligating major uterine vessels affects
uterine blood flow in later pregnancies. Another possible explanation is
abnormal placentation secondary to the uterine scar.