VIRGIN BIRTHS

According to the results of a long-term study of reproductive health, published in the British Medical Journal, one in two hundred women in the United States reported being pregnant and giving birth without ever having sexual intercourse. 

7,870 women between the ages of 15 and 28 were studied as part of the National Longitudinal Study of Adolescent Health, between 1995 - 2009.  Of those 7,870 women, 45 reported at least one pregnancy "unrelated to the use of assisted reproductive technology."
Researchers at the University of North Carolina at Chapel Hill found that the women who claimed virgin pregnancies shared some common traits. For example, 31% of those studied had signed a "chastity pledge," vowing not to have sex, usually citing religious reasons. 15% of non-virgins who became pregnant claim to have made similar vows.
36 of the 45 women claiming virgin pregnancies told researchers their parents never or very rarely spoke with them about sex or birth control. When researchers interviewed the parents of the women studied, 28% suggested they had insufficient knowledge of sex and contraception to discuss those subjects with their daughters.  Only 5% made this claim among the parents of those who said they had intercourse.
The authors of the "Like a virgin (mother)" say that in the wake of these scientifically impossible claims, researchers must interpret self-reported behavior by taking into account fallible memory, beliefs and wishes.