Though some women worry that labor and delivery will harm their sex life after pregnancy, a new study finds no evidence that childbirth itself affects a woman’s long-term sexual function.

Instead, researchers in the Netherlands found, the biggest predictor of a woman’s post-baby sex life was her sex life before the baby.

Of the 377 first-time mothers they followed, those who were not having sex early in pregnancy were more likely than other women to still be sex-free when their babies were a year old.

Dr. H.J. van Brummen and her colleagues at University Medical Center Utrecht report the findings in the obstetrics and gynecology journal BJOG.

There has been little research into how the type of delivery may affect a woman’s postpartum sexual function, according to van Brummen’s team. However, they note, reports in the “popular media” suggest that many women worry that vaginal delivery will harm their sexual function.

And there is some reason for concern, the researchers add. One research review found that vaginal delivery with the use of forceps or vacuum assistance could make sex painful for some time after childbirth.

To study the question further, van Brummen’s team followed 377 women from the 12th week of pregnancy until one year after childbirth. During and after pregnancy, the women completed questionnaires on their sexual activity and satisfaction with their sex life.

Overall, the researchers found, the women’s sex lives one year after childbirth were unrelated to the type of delivery they had - whether vaginal, vaginal delivery with forceps or vacuum, or Cesarean section.

But women who weren’t having sex at week 12 of pregnancy were 11 times more likely than other women to be sexually inactive one year after childbirth. The only other factor that affected long-term sexual function was significant tearing in the anal sphincter during childbirth; the 6 percent of women with this injury were five times less likely to be sexually active one year later.

It’s not clear why some women weren’t having sex early in pregnancy, or why for some women, the pattern remained long after childbirth. Sexual activity early in pregnancy may be a reflection of sexual function before pregnancy, the researchers note, but the study did not assess the women’s pre-pregnancy sex life.

In all, van Brummen and her colleagues point out, 94 percent of women were having sex one year after giving birth. That included a majority of those who’d abstained during early pregnancy or who’d suffered an anal tear during delivery.

SOURCE: BJOG: An International Journal of Obstetrics and Gynecology, August 2006.