Cesarean delivery performed in a first pregnancy appears to increase the risk of complications in later pregnancies, researchers have shown.

The findings 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.

Compared to a vaginal first birth, a cesarean delivery at first birth approximately doubled the risk in a second pregnancy of a woman developing pre-eclampsia, placenta abnormalities, and having a small baby, according to a report in the June issue of Obstetrics & Gynecology.

However, Dr. Anne Kjertsti Daltveit, from the University of Bergen in Norway, and colleagues emphasize that a woman's obstetric history must be taken into account. They found that if the same complications were excluded from the first birth, the risks in the second pregnancy fell slightly.

With two prior c-sections, the risk of complications in the third pregnancy was increased, but the odds were similar to those seen after one prior c-section, the report indicates.

"An increased risk of complications after a cesarean delivery may be caused by the cesarean delivery itself," the researchers write. On the other hand, they explain, it is just as possible that the reasons for performing the first cesarean delivery may also be present in subsequent pregnancies, thus accounting for the complications seen.