One evening at the end of my second trimester, I was standing in the dairy aisle of the grocery store, with one hand on my back and the other over the kicking baby in my distended belly. A young man approached me, initiated a conversation about the World Cup, and, casually, asked me if I'd like watch the game with him that weekend. "You're pretty!" he whispered. I was shocked.

I wasn't putting out a sexy vibe. (Not at all.) I had assumed that any male I receive in late , including that from my husband, would be friendly, not sexual. Why would a man who is not the expectant father think pregnancy is sexy? But then other women told me similar stories about how they got hit on in third trimester. So I decided to look into it, and it turns out that a study on sexual to pregnancy has recently come out.

A team of Swedish and Italian doctors, led by Emmanuele Jannini and Magnus Enquist, recruited nearly 2,200 men who had joined online fetish groups such as alt. .fetish and alt.sex.fetish.breastmilk. They presented a questionnaire that asked the respondents questions about their preferences for pregnant and lactating women. The survey also asked for the sex and age of each , and whether the sibling is a full sibling or not (half-sibling or adopted child). Most respondents reported both a pregnancy and a lactation preference. The average age at which respondents became aware of their preference was about 18 years.

What Jannini and Enquist and their colleagues were searching for was evidence that there was something special about the upbringing of men that are sexually aroused by pregnancy. They knew that a specific stimulus early in life can elicit sexual behavior when that animal reaches sexual maturity. For instance, goats that are raised by sheep are sexually aroused by sheep only. This is called sexual imprinting.

Is it possible that boys that are raised by women who are pregnant (or nursing) are especially attracted to pregnant (or nursing) women?

It turns out, what's good for the goat is good for the guy. The more exposed a man was to his mother being pregnant and breastfeeding when he was between 1.5 and 5 years old, the more likely he is to be sexually attracted to pregnant and breastfeeding women.

A younger sibling is the key to early exposure. The respondents who eroticized pregnancy and breastfeeding had significantly more younger siblings than expected by chance. Respondents with one sibling were older than their sister or brother in 66 percent of cases. Interestingly, siblings born of a different mother does not appear to be related to respondents' sexual preferences (likely because a stepmom, for instance, isn't a boy's primary mother figure). Only a boy's own pregnant mother seemed to leave a sexual imprint.

's "oedipal phase," from about 3 to about 5-6 years of age, only overlaps partially with the sensitive period suggested by this study's data, the researchers are careful to point out. Sexual imprinting is different in that it's motivated not by sexual drive but because the individual learns what's normal during a sensitive phase of development and later seeks sexual partners that resemble his (or her) own parents.

What does this mean for women who are pregnant or plan to be pregnant? It means you may be able to predict how attracted your partner will be to you in late pregnancy. Does he have sibling who was born within five years after him? If so, he's likelier to be turned on by your pregnant self.

As for the guy I met in the dairy aisle, I'd wager he had a younger brother or sister. I'd bet more on getting this right than the winner of the next World Cup.