Dec. 18, 2013 -- Just in time for Advent and the birth of Christ, researchers at the University of North Carolina at Chapel Hill have reported 45 virgin births -- without a holy ghost in sight.
An analysis of a national population survey of 7,870 American adolescents and young adults in 1995 and again in 2008 and 2009 found that one half of 1 percent of women reported they'd never had sex but had been pregnant.
The tongue-in-cheek article, "Strange Nativities," was published in the December issue of the British Journal of Medicine.
Except for in the Bible, virgin births or asexual reproduction occur only in the plant world and among a small group of vertebrates: pit vipers, boa constrictors, sharks and Komodo dragons, according to the BMJ article.
"We weren't at all looking for virgin births," said co-author Amy H. Herring, a professor of biostatistics at UNC's Gillings School of Global Public Health.
"We were analyzing data for a separate project -- people who were still virgins once they were adults. But we were surprised to discover a number of them reported pregnancies. Once we confirmed these were not programming errors, we thought there were some interesting factors."
These seemingly miraculous births were not a result of in vitro fertilization, according to the survey results. The authors also said the findings suggest the need for more -- and better -- sex education.
"We found [the "virgin birth" phenomenon] was more common among women who signed chastity pledges or whose parents indicated lower levels of communication with their children about sex and birth control," said Herring.
The immaculate conception group may have been small, but researchers did find an even larger group, whom they called "born again virgins."
"They reported in an earlier study a pregnancy, then later said they were virgins," said Herring. "Those may have been a misclassification issue."
Women were not asked "specifically" if they'd given birth as virgins, said Herring. Rather, they were asked separate questions about their virginal status and their pregnancy history.
"We don't know if the data was collected incorrectly. Women entered their answers on a computer," she said. "Many of the participants might not have known they answered inconsistently. Someone may have gotten the date wrong or mixed their date of marriage with their child's birth."
But, said Herring, researchers did find some common denominators among these women -- most notably, their conservative ideas about sex. "Some of these women did not want to admit they'd had vaginal intercourse," she said.
For the larger original study in 1995, which included both males and females, she said scientists were surprised by some of the findings. "There were a few virgin fathers lurking around in data field," said Herring.
Researchers did come to one other conclusion: There are a lot of challenges in collecting and analyzing self-reported data on "potentially sensitive" topics.
"As a scientist," said Herring, "what's interesting to me are there are lots of different things we can study only by self-reporting. If am analyzing diet data, is it one scoop of ice cream or the whole pint" that someone's reporting?