When it comes to conception, there are plenty of rumors floating around about the best sex positions if you want to end up with a boy or tricks to conceiving a girl. The problem is they’re just that — rumors — and not in any way informed by science or medicine.
And it’s not just me discounting your friend’s advice to have sex against the wall, upside down, then jump on one leg for 10 minutes — it’s coming from doctors. According to Dr. Aaron Styer, a reproductive endocrinologist, founding partner and co-medical director of CCRM Boston, there is currently no evidence that conceiving a boy or a girl is more likely with specific sexual positions.
“Sperm has the same size and weight, and same speed of swimming whether it contains [an] X or a Y chromosome, and there are no known sex positions, foods, etc., that affect which chromosome[s] containing sperm are more likely to end up in the woman’s womb and fallopian tube,” Dr. Salli Tazuke, the co-founder and co-medical director of CCRM San Francisco told SheKnows. “It is pure chance of 50-50.”
So what can you do if you want to conceive naturally and attempt to control the biological sex of your baby?
Not much, it turns out.
“In reality, there are no foods, lifestyle habits or methods before, during or after sex that will influence the sex of the baby conceived,” Styer explained. Rather, the sex of the baby is determined at the time when the woman’s egg is fertilized by sperm. The unfertilized egg carries an X chromosome, while the sperm can carry an X or a Y chromosome.
“If sperm carrying an X chromosome fertilizes the egg, a girl or female (XX) will be conceived,” he added. “If the sperm carrying a Y chromosome fertilizes the egg, then a boy or male (XY) will be conceived.”
Aside from the idea that certain sex positions will result in conceiving boys or girls, there are plenty of other fertility myths floating around. One Tazuke has encountered in practice is the notion that sperm that will result in conceiving a boy will swim faster and die sooner, so if you want a boy, it’s best to have sex on the day of ovulation in the missionary position to allow the sperm to be closer to the egg.
Turns out, sperm can survive in the genital tract up to six days in a woman, while the egg is only good for fertilization for about 24 hours after ovulation. She said that this myth is not true and again, “a pure chance.”
What do these physicians tell their patients who may believe in these myths/claims that come with no medical evidence?
“Wish we had so much control over our body and biology!” Tazuke said. “There is always ‘natural selection’ and the best egg/sperm ends up as an embryo that grow[s] and implant[s] to hopefully become a healthy baby, whether it is a girl or a boy.” She added that in the end, it’s a good thing we don’t “because in certain cultures, a certain sex offspring is favored and we would end up with too many of boys (or girls) and be very skewed.”
Styer has heard it all when it comes to myths surrounding foods to eat to control conception. Specifically, to influence the sex of the baby, he has heard misconceptions including that foods rich in potassium and sodium help you conceive a boy, while foods that are high in calcium and magnesium increase your chances of having a girl. Again, these are just myths.
Styer said he begins his discussion with his patients “by reviewing what we know is most effective for conception: The ideal time of intercourse should ideally begin four days prior to the day of ovulation and continue through the day of ovulation.” He then reassures them that myths surrounding conception are very common, yet unproven, and will not improve their success and reviews that there is no reliable evidence to support the benefits of specific foods, medications or sexual activities.
Is there anything that does work?
According to Styer, “The best lifestyle interventions to optimize fertility include a well-balanced diet, taking a multivitamin supplement which include[s] folic acid, daily recommended vitamin D and calcium, maintaining an appropriate body weight, abstinence from tobacco and recreational drugs and avoiding excessive caffeine intake.”
This is also a great time to point out that no matter what genitalia your baby emerges with from the womb, it may not match their gender identity. All these myths surrounding influencing the biological sex of your baby can be damaging and hurtful to those dealing with gender dysphoria, so let’s keep that in mind when discussing conception and reproduction.
A version of this article was originally published in August 2017.