Quick: When should you have sex if you’re trying to get pregnant? Feel pretty sure about that answer? So did the 204 “infertile” women in a study conducted by researchers at two Australian infertility clinics. Unfortunately, almost all of them were wrong. In fact, only 13 percent of the women could identify the precise days on which they were most likely to conceive. This despite the fact that 68 percent of them insisted they’d properly and accurately timed having sex to maximize conception before seeking help at the clinics.

In fact, lead study investigator Kerry Hampton of Australia’s Monash University says a lack of awareness of when in a woman’s menstrual cycle she’s most likely to conceive could be a major cause of infertility, which affects one in six Aussie couples and 11 percent of couples in the U.S. “Accurately timed intercourse on fertile days of the menstrual cycle may reduce the time it takes a couple to get pregnant,” Hampton said, and could help them avoid assisted reproductive technology like in vitro fertilization.

Eighty-seven percent of the women in the study said that after they decided they were infertile—which is clinically defined by a lack of conception within a year of trying—they sought information on when they were most likely to conceive. The most common informational sources were the Internet and books.

Considering that a lack of decent, factual sex ed may actually be keeping women from conceiving, you’d think right-wingers would be in favor of it, wouldn’t you?

So, anyway … you’re most likely to become pregnant when you have sex on the day you ovulate and the two days preceding ovulation, which most often occurs 14 days before the start of your period. How’d you do?