From medscpae today...
"NEW YORK (Reuters Health) Jun 17 - Cesarean delivery in a first pregnancy increases the risk of preeclampsia, placenta previa, and other complications in later pregnancies, according to a report in the June issue of Obstetrics and Gynecology.
However, lead author Dr. Anne Kjertsti Daltveit, from the University of Bergen in Norway, and colleagues emphasize that obstetric history can have a confounding effect on the risk assessments and must be taken into account.
The results stem from an analysis of Norway registry data for 637,497 first and second births in women with at least two single births and 242,812 first, second, and third births in women with at least three single births.
Relative to a vaginal delivery at first birth, a c-section at first birth increased the second pregnancy risk of preeclampsia by 2.9-fold, small for gestational age by 1.5-fold, placenta accreta by 1.5-fold, placental abruption by 2.0-fold, and uterine rupture by 37.4-fold.
However, if the same complications were excluded from the first birth, the risks fell slightly. With the exception of uterine rupture (OR = 37.2), the new odds ratios did not exceed 1.9. The reduction in c-section numbers needed to prevent one case ranged from 56 for small for gestational age to 3706 for placenta accreta.
With two prior c-sections, the risk of complications in the third pregnancy was increased, but the odds ratios were similar or lower than those seen after one prior c-section, the report indicates. Once again, excluding women with the same complication in prior pregnancies reduced the odds ratios.
"An increased risk of complications after a cesarean delivery may be caused by the cesarean delivery itself, or alternatively it may be a result of confounding by indication; persistent problems that represented the indication of the first cesarean delivery also may be present in subsequent pregnancies," the authors conclude.
Obstet Gynecol 2008;111:1327-1334."