One in every 200 women in America have reported having a "virgin pregnancy."

Researchers in the US looked through the results of a long-term study into reproductive health among young people and they say they were surprised by the number of women claiming they'd conceived without intercourse.

Nearly a third of those women said they had made a so-called chastity pledge for religious reasons and hadn't broken it.

The study's authors say this points up a possible lack of sex education among women, or at least the difficulty in getting accurate sexual histories from participants.

The researchers said they were also surprised to find a few men who claimed they'd fathered kids without doing it.

--Rob Archer