VIENNA -- Having a Cesarean section can make it more difficult for women to get pregnant again and could delay conception for more than a year, British scientists said on Tuesday.

They found that women who had had a Cesarean were nearly twice as likely to take a year or more to conceive again as mothers who had given birth normally.

"We looked at the delayed ability to conceive of women who did eventually go on to get pregnant. This may be underestimating the true magnitude of the association," said Dr.

Deirdre Murphy of the University of Bristol in western England.

In research presented to the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE), Murphy and her colleagues said other factors such as the age of the mother and father, the use of oral contraceptives and smoking and drinking could not account for the difference.

Their study involved data on 14,541 pregnant women.

Murphy believes the findings, which are reported in the journal **** Human Reproduction ****, could have important implications because the number of women having Cesareans is increasing.

In Britain, one in five women has surgery rather than a vaginal birth, according to the Royal College of Obstetricians and Gynaecologists (RCOG).

Health officials have expressed concern about the increasing number of Cesarean births because they can lead to complications such as bleeding, uterine infections and other problems.

Murphy said some women may choose not to have another baby because of the trauma of a Cesarean or will fail to get pregnant if they try.

Professor James Walker, of the RCOG, said the Bristol research is not the first study to indicate a Cesarean section may affect a woman's fertility.

"Neither the medical profession nor women themselves realize the extent of the long-term problems Cesarean sections can cause," he said in a statement.

"When doctors and mothers assess the risk of Cesareans they generally only think about what the risks are at the time and ignore the impact they might have five years down the line," Reuters quoted Walker as adding.

In some cases Cesareans are necessary to deliver the baby safely, but health officials are worried that women and doctors are choosing to have Cesareans for convenience or to avoid the pain of labor and a vaginal birth.

Murphy called for further studies to confirm her findings, saying more reliable evidence is needed on the long-term consequences of the operation.