No proof sex brings on labour

For a long time women have been told that having sex late in their pregnancy can help bring on labour, but a new study had put that theory to rest.

Dr. Peng Chiong Tan of the University of Malaya in Kuala Lumpur, Malaysia and colleagues found that women who had sex a few days before they were scheduled to give birth were no more likely to go into labour spontaneously than other women.

But Tan this was not the final word on the subject.

"It is possible that regular sex a little earlier on, say from 36 to 37 weeks onward might have a different effect," Tan said.

There are good biological explanations for the widespread belief that having sex can bring on labour, Tan and colleagues wrote in the medical journal Obstetrics and Gynecology.

For example, semen contains the hormone prostaglandin, which is used to induce labour, while orgasm can bring on contractions in the uterus.

But there is virtually no scientific evidence that sexual intercourse near the end of pregnancy can jump-start labour.

To investigate, the investigators randomly assigned 210 women scheduled for labour induction to a group who were advised to have sex as much as possible before their induction, or to a control group who were told that it would be safe for them to have sex but that it wasn't clear whether intercourse could bring on labour.

Women received the advice 4.7 days before their induction was scheduled, on average.

Among the 108 women advised to have sex, 60 per cent did so, compared to 40 per cent of the 102 women in the control group.

But among women who had intercourse, 56 per cent went into labour on their own, compared to 52 per cent of those who didn't have sex, which was not a statistically significant difference.

"We speculate that women very close to spontaneous labour felt changes coming on that might reduce their libido," for example pains and vaginal discharge, Tan said.

"If correct, this would mean that those women who had sex were the least likely to go into spontaneous labour soon, so they would do less well in terms of spontaneous labor as outcome in the next few days. We did not have direct data to answer this question satisfactorily, however."