The Immaculate Conception may not just be for the Virgin Mary. Scientists from the University of North Carolina at Chapel Hill have discovered 45 women who claimed they were pregnant without having sexual intercourse.

Researchers analysed a national population survey in 1995 of 7,870 young adults and adolescents. They also examined the population data in 2008 and 2009. Based on the surveys, researchers found that 1 per cent of the women reported not having any sexual contact but had been pregnant.

The report with the title, "Strange Nativities", was published in the latest issue of the British Journal of Medicine. According to the article, "virgin births" or asexual reproduction happens only to plants and a small group of animals like boa constrictors, pit vipers, Komodo dragons and sharks. The only other incidence of a recorded virgin birth was written in the Bible.

Co-author of the report and UNC biostatistics professor Amy Herring said the researchers were not looking for virgin births since they were working on a different project which was looking for people who were still virgins as adults.

Ms Herring said they were surprised to see a number of people who reported being pregnant while remaining a virgin. Once the researchers determined there were no errors in encoding the data, they set out to find interesting factors.

The population survey results indicated that the virgin births were not due to in vitro fertilisation. Researchers found that "virgin births" were more common in women who had parents who said they have little communication with their children about sex education.

The women may have been asked two separate questions for the survey. The 1 per cent of women who reported virgin births may have said they were pregnant in a study about pregnancy then later saying they were virgins in a separate study.

Researchers said it might have been a "misclassification issue." The women were not asked specifically if they were virgins when they got pregnant. The team was not sure if there was a mistake in gathering data. Some women might have answered inconsistently while some were confused about the marriage date and birth.

Researchers also noticed that the women who claimed to have virgin births were in denial that they had vaginal intercourse.