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?

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    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

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    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!