Nativity scene following birth of Jesuswiki commons

Over the next week, the nativity story of the Virgin Mary giving birth to Jesus will be told countless times.

However, while the phenomenon of virgin pregnancies has been widely studied in the animal kingdom – normally through asexual reproduction – among humans it has received little attention.

As a result, a team of US researchers have looked at virgin births among women since the mid-1990s.

Published in the BMJ, researchers based at the The University of North Carolina at Chapel Hill identified a number of pregnancies where the women said they had never had sex.

They analysed data on 7,870 women who were interviewed confidentiality and numerous times over 14 years between adolescence and adulthood as part of the US National Longitudinal Study of Adolescent Health.

Researchers were looking for the incidence of pregnancy before the onset of sexual intercourse, as well as characteristics shared by these virgin mothers.

Participants reported their sexual history, including sexual intercourse, use of reproductive technology and pregnancy history. This information was used to classify women by their virginity status at the time of their pregnancy.

Of the study participants, 0.5% consistently affirmed their status as virgins yet somehow fell pregnant.

Looking at characteristics of the virgin mothers, findings showed they were around a third more likely to have signed a chastity pledge than non-virgins.

Their parents were also less likely to have spoken with them about sex and birth control.

While the authors conceded that the study was problematic because it relies on self-reporting on sensitive topics, they concluded that "around 0.5% of women affirmed their status as virgins and did not use assisted reproductive technology, yet reported virgin births".

"Reporting dates of pregnancy and sexual initiation consistent with virgin pregnancy was associated with cultural mores highly valuing virginity, specifically signing chastity pledges, and with parental endorsement of items indicative of lower levels of communication about sex and birth control," the authors concluded.