Can We Select the Sex of Our Baby?

Since ancient times mankind has attempted to choose the sex of a child before its birth. Countless myths, folk remedies and magical potions were offered as solutions. Some authorities advised couples to change the time of intercourse, apply douches or alter their diet to ensure the conception and birth of either a male or female infant.

Sperm cells carry either an X chromosome, resulting in a female, or a Y chromosome, resulting in a male.

Sperm cells carrying X chromosomes have different biophysical properties from those carrying Y chromosomes. The sperm cells carrying Y chromosomes have smaller heads, are lighter and have 3% less DNA. Their different properties can be used to separate X and Y chromosome-bearing sperm cells.

The scientific study of sex selection techniques dates from the 1970 discovery that a male, or Y chromosome-bearing, sperm could be stained with a dye allowing for sperm identification. Techniques for the separation of X and Y chromosome-bearing sperm have been tested in selected populations, with varying results.

The most common sex selection technique is based on the premise that sperm cells bearing a Y chromosome move faster than those bearing an X chromosome. Sperm cells are incubated in a sperm wash column, a tube with a viscous protein liquid, to separate the two populations of sperm cells.

During this process, more Y-bearing sperm will speed through the sperm wash column than X-bearing sperm. By repeating this process, a higher percentage of Y-bearing sperm (or X-bearing sperm) may be separated out from the original specimen.

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