Girl or Boy: What Determines the Gender of a Baby?

    Artwork Jane Choi|CC

    Can a mother influence whether she has a boy or a girl, or is it all up to dad?  Read about what determines the gender of a baby, and the biological odds of changing that one special sperm.

    What Determines the Gender of a Baby?

    Genetics determines whether a baby will be a girl or a boy.  Girls have two X chromosomes (XX), and boys have one X and one Y chromosome (XY).

    Whether a baby will be a boy or a girl is determined at the time of conception. This is when a single male sperm fertilizes the female egg.

    Read more about What is a Chromosome?

    Does the Mother or Father Determine the Baby’s Gender?

    A father’s sperm determines a baby’s gender.

    A mother’s egg carries only an X chromosome, while a father’s sperm either carries either an X chromosome, or a Y chromosome.

    The average male ejaculation contains a whooping number of 200 million – 500 million sperm.  But only one of these sperm will ultimately fertilize an egg. That’s about 1/250,000,000!!!

    With so many sperm, it is statistically impossible to change the 50:50 ratio of girl (X chromosome) to boy (Y chromosome) sperm. The natural biological odds for a girl or a boy is always 50/50 — though a little prayer and good luck certainly won’t hurt.  Read more…Myths of Natural Gender Selection: The Sperm Race to Nowhere

    There are no diets, or exercises, or underwear, or acrobatic sex acts that can change that ONE sperm in 250,000,000. To scientifically change the odds of having a girl or a boy, there are only two methods proven via clinical trials:  sperm sorting or preimplantation genetic diagnosis (IVF/PGD).

    Parents throughout the centuries have tried all kinds of tricks to influence the natural 50:50 ratio of X and Y chromosomes in sperm. These old wife’s tales about gender prediction are quite entertaining, though scientifically, they’re poppycock!