Pick Your Pregnancy

Your baby's gender is still a game of chance.

Can you defy the odds? Though the sex of a child seems random, it may all boil down to natural selection. A recent hypothesis believed that women are able to adjust their offspring’s sex based on their state of health. But based on the mating patterns of bighorn ewes, moms-to-be don’t seem to have much choice in the matter (without a helping hand from a fertility doctor, that is.) As biologist Peter Neuhaus states, “Evolution is very complex. To understand how it works, you need to take into account as many factors as possible that could influence reproduce potential.”

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  • Kiley

    This is bizarre. The sex of a baby is determined by the sperm, the eggs are always gonna be x whereas sperm can carry x or Y chromosome. How on earth can a woman somehow change this? Also using gender and sex incorrectly in this article. Please do your research.

    • Heather!

      Great question! I am by no means any kind of expert, but was fascinated by your question. I also remember a very old study that find female mice who experienced great stress during pregnancy tended to have more daughters than sons, and that has always interested me. I found some info that might clarify how the Trivers-Willard Hypothesis works. Basically, it ain’t quite as simple as basic biology classes would indicate.

      There are several conditions that can determine or influence the sex of offspring. First, there are people whose chromosome set differs from phenotype (physical expression). So somebody might be seen as and considered to be male, but ‘his’ chromosomes suggest femaleness. I don’t know anything about this myself, so please forgive if my vocabulary is misleading or inaccurate. Neither do I know how often this happens.

      Also, the development of male offspring actually requires more than just a Y chromosome. The Y carries a gene (SRY, I think?) that sort of flips a switch to activate male development and Y expression. This doesn’t always happen, which could affect the expression of ‘maleness’. And female offspring have undergone the process of X-inactivation, which suppresses the expression of one set of X chromosomes. This means that sex can be said to be partly determined by the behavior of X chromosomes, too.

      These are just ideas rolling around in my head. You might find this guy a lot more informative:

  • Meaghan Berry

    It’s absolutely bizarre. God decides the sex of your baby not man. Nice try though daily aha!

  • Dilcia

    To Rebekka Spiller This must have been your daily ha ha for us. Thanks 🙂 you’ve left me chuckling.

  • Aimee Kelly

    If you cited the original article, (which you did not) you’ll see that this theory is not well supported. Some of these You Beauty articles are so stupid. You just pluck any old research regardless of how credible it is and peddle it as truth. Considering how your audience is that’s a bit irresponsible. You don’t even read the original research! Surely Dr Oz can hire better people than this!

  • MissEntropy

    It really isn’t that bizarre. Baby boys are more fragile than baby girls, just look at the sex ratio in any NICU. The healthier the mother is, the more resources are available for the fetus. Many females are necessary for the perpetuation of the species while significantly few males are needed and therefore the resulting male should be the healthiest it can in order to survive to sexual maturity and pass on its genes. While the male is responsible for producing X or Y sperm, the mother’s body can help or hinder the sperm by changing pH, the thickness of the cervical mucus, etc to ultimately affect whether and X sperm (which is heavier) or a Y sperm successfully fertilizes the egg, determining the baby’s sex.

  • Cme

    Science or opinion? Valid reports typically site their sources. What happened to chromosomes determining gender. Does a woman’s body attract y chromosomes if it’s healthy?

  • Erin B

    My last comment was removed, for some strange reason, so I’ll try again. This time I’ll be more specific.

    If you click on the research link reported in this article, you will find that it doesn’t support what the article is saying. Swiss researchers looked at bighorn ewes, to test the hypothesis that healthy ewes would have more sons, and they found that it didn’t happen. “Healthy females did not produce more male offspring.”

    Am I missing something? Because it seems like this article is saying the opposite of what the supporting research says.

    • YouBeauty

      Thanks so much for bringing this to our attention, Erin—we truly welcome and appreciate thoughtful reader feedback and criticism. We have corrected this mistake, and apologize for the oversight in reporting. Have an awesome Friday!