Sex Question Friday: Can Intercourse Position And Timing Affect The Sex Of Your Child?
Dr. Justin J. Lehmiller Posted on Friday, August 10, 2012 at 6:01AM 
Every Friday on the blog, I answer people’s questions about sex, love, and relationships. This week, we’re talking about whether you can pick the sex of your baby by having sex in certain positions or by timing how closely you have sex to when a woman ovulates. It appears that a lot of people are interested in learning about this topic because questions of this nature have come up with surprising frequency among students in my classes!
Can different sexual positions determine the sex of a child?
Can timing intercourse in relation to ovulation affect whether you have a boy or girl?
People have believed for centuries that when, where, and how a heterosexual couple has intercourse can determine their baby’s sex. Such beliefs persist today, where it’s easy to find how-to guides for conceiving a boy or girl in bookstores and online. I just did a quick Internet search and found a huge number of pages advocating everything from “how to conceive a girl in three steps” to “how to have a boy.” These and numerous other articles promote the idea that you can pick your baby’s sex by modifying a woman’s diet (eat more red meat if you want a boy and more cheese and yogurt if you want a girl), changing the timing of intercourse (have sex closer to ovulation for a boy and further from ovulation for a girl), and limiting yourself to a specific sexual position (shallow penetration for girls and deeper penetration for boys).The websites I consulted made it sound as if all of this information was factual and scientific—but is any of it true?
According to actual research, no. First, there is no link between timing of intercourse relative to ovulation and the sex of the child conceived.1 Having sex close to ovulation obviously increases your chances of becoming pregnant—but timing it closer or further from ovulation won’t affect your child’s sex. Second, although some scientists have claimed that the mother’s diet is associated with a child’s sex, the research I’ve seen on this topic is fraught with problems. For example, one recent study received a lot of media attention because it found that 80% of women following a specific diet ended up conceiving girls. However, this was a correlational study, which means we can’t draw any conclusions about cause and effect. Plus, nearly 88% of the women participating in the study dropped out before the end, which means that the findings were ultimately based on a total of just 21 women, which hardly makes for a random or representative sample. Thus, it’s hard to draw firm conclusions from research like this. And finally, as for sexual position, I was unable to find any published research suggesting that how you make love might impact a child’s sex.
So why are these beliefs so widely held and promoted even though they’re clearly wrong? Part of the reason is because people are much more convinced by personal anecdotes than they are by actual data (i.e., people trust the stories that their families and friends tell them more than what’s published in scientific journals).2 Thus, if a certain diet or position “worked” for your friend, you’ll be tempted to believe that there’s something to it, even if the statistical data doesn’t support it. Another reason these ideas are promoted so heavily is because many people are desperate to have a child of a certain sex and some disingenuous individuals are taking advantage of others’ desperation in order to make a quick buck.
The only want you may be able to determine the sex of your child with a high level of accuracy is to engage in some high-tech sex selection (i.e., in-vitro fertilization in which only embryos of the desired sex are implanted). However, such procedures are expensive, they aren’t guaranteed to work, and they raise some important ethical questions (e.g., Is it really appropriate to value one sex over the other? And if this became a widespread practice, what would it do to the sex ratio?).
The take home message from all of this is to steer clear of all of those “how to have a girl/boy” guides. The reality is that we have little control over the sex of our children, so it’s not worth stressing yourself out over it. So just sit back, relax, and enjoy the surprise!
For past Sex Question Friday posts, see here. Want to learn more about The Psychology of Human Sexuality? Click here for a complete list of articles or like the Facebook page to get articles delivered to your newsfeed.
1Wilcox, A. J., Weinberg, C. R., & Baird, D. D. (1995). Timing of sexual intercourse in relation to ovulation: Effects on the probability of conception, survival of pregnancy, and sex of the baby. New England Journal of Medicine, 333, 1517-1521.
2Fagerlin, A., Wang, C., Ubel, P. A. (2005). Reducing the influence of anecdotal reasoning on people’s health care decisions: Is a picture worth a thousand statistics? Medical Decision Making, 25, 398–405.
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Reader Comments (2)
Interesting! Another great read. What is the scientific explanation for the unequal ratio of girls (49%) to boys (51%). Is this ratio even correct?
Is it true that the y-chromosome carrying sperm "swim" faster?
Thanks!
Great follow-up questions! Regarding the sex ratio, it's a fairly consistent finding around the world that more boys are born than girls. Why is that? We don't know for sure, but one reason I've often heard is that sex selective abortion in China and India favor more male births. However, even if you look at countries where sex selection is far less likely to occur, you still find a lopsided sex ratio with more male births, so there's something else going on, which points to sperm differences. I've read some theories (and keep in mind that these are just theories) that humans have evolved a tendency to conceive more males than females because boys are much more likely to die during childhood and adolescence (e.g., because they are more likely to go off to war, to engage in risky behaviors, etc.). So, maybe this is nature's way of "evening out" the sex ratio, which currently favors men at birth and women in old age. So are more boys conceived because Y-carrying sperm "swim" faster? I think that's unlikely because the research I've seen has found no differences in swimming speed between X- and Y-carrying sperm (Penfold, Holt, Holt, Welch, Cran, & Johnson, 1998). But there may be other differences between these sperm cells we have yet to discover than explain why male conception is more likely.