Her team was looking at data for 7,870 women interviewed multiple times over 14 years, from their teen years to adulthood, as part of the U.S. National Longitudinal Study of Adolescent Health.

About 45 consistently stuck to a story that they had given birth before they ever had sex. …

But science has never demonstrated a human case of parthenogenesis. Herring thinks it may all be a mistake. “It’s self-reported pregnancy,” she says. And the survey, given by computer so the women and girls would feel free to answer questions honestly, didn’t follow up and ask them “Are you sure?” if they reported having had a baby yet not ever having had sex.