Can a woman get pregnant if she isn’t menstruating? Or another way of asking it is: Can a woman assume she doesn’t need to use birth control because she isn’t having periods? Or can she get pregnant if she is trying to conceive, even if she isn’t having periods? In both cases, the answer is not as intuitive as you’d think. On the surface, any self-respecting educated person might think “Of course she can’t get pregnant if she’s not having periods! What a ridiculous question.”

Surprisingly, the answer is that yes, she could theoretically, but certainly not as likely as the average woman. Since a woman releases an egg about 14 days before menstruation, in theory it is possible to get pregnant without actually having periods! Thus, women who are not menstruating for whatever reason, (excessively low body fat, breastfeeding, being premenopausal, etc.), are always in a potential state of impending ovulation. This is because the underlying condition causing the lack of menstruation could change at any time, thus unexpectedly triggering the release of an egg.

The bottom line is that women who don’t menstruate cannot count on their condition as reliable contraception, nor should a woman trying to get pregnant assume that she can even though she isn’t cycling. In fact, the only practical way to know if ovulation is approaching is through charting your cycles, and more specifically, observing your cervical fluid evolve into a wet slippery secretion, followed by a thermal shift.

Of course for those couples desiring to get pregnant, the reality is that you will definitely want to resolve the underlying problem preventing menstruation. Until you do so, your chances of conception will be extremely low.

So the next time you’re at a cocktail party, try this menstrual puzzle on others and see what they think. Or not.