A good friend of mine was ecstatic to have the baby girl she had always wanted when she found out she was pregnant last year. Her excitement had her feeling like she knew for sure that a little girl was on the way, so you can imagine her disappointment when the telltale ultrasound appointment crushed her hopes. She was having a boy. Now, she couldn’t be happier, but I can tell it’s only a matter of time before she tries again. After all, you can’t buy dresses and bows for a little boy—at least not without a few stares in public.
When I started thinking about her situation, I wondered if controlling the gender of your baby naturally was possible. She would never pay for gender selection under a doctor’s procedure, but I know she’d be disappointed if baby number two was also a boy. As it turns out, research shows that controlling your baby’s gender naturally is not impossible. Unfortunately, it’s difficult to measure which methods worked because there are so many factors that could affect a baby’s development, but the timing of fertilization is the most reliable method, and it makes sense biologically.
Before understanding how the timing works, you should first understand how a baby’s gender is determined in the first place. To conceive, a woman needs to be ovulating, which means her egg needs to become available for fertilization. This happens in the middle of every menstrual cycle. Then, a man’s sperm, which either carries an X chromosome for a boy or a Y chromosome for a girl, must fertilize the egg. Male carrying sperm are fast swimmers but die quickly. Female carrying sperm are resilient.
If you and your partner try to conceive on the day of ovulation, it is more likely that you will have a baby boy because the X chromosome sperm will reach the egg first. On the other hand, having intercourse one or two days before ovulation means sperm will have to live inside the reproductive tract for a while, at which point the male sperm will die off and the female sperm will thrive.
When you’re trying to have a baby girl with your partner, plan to make your attempt before ovulation once you have calculated that. If you’d prefer a baby boy, try conceiving during ovulation. It isn’t guaranteed, but it certainly can’t hurt to try either way.
Source: AM Noorlander et al: Female Gender Pre-Selection by Maternal Diet in Combination with Timing of Sexual Intercourse – A Prospective Study. Reproductive BioMedicine Online Volume 21 Issue 6 pp. 784-802 December 2010