Couples who want to choose the sex of their child have historically turned to unreliable methods in an attempt to achieve this goal. Popular but unproven approaches typically rely on the theory that Y bearing sperm swims faster or that X bearing sperm is hardier.
The Whelan and Shettles methods are implemented at a home by timing intercourse to occur on specific days around a woman’s ovulation cycle. Proponents of these techniques sometimes claim that sexual position is also important for success. The idea is to give sperm carrying the desired sex chromosome a better chance of making it to the egg. There is little evidence that these gender selection techniques affect the usual 50/50 chance of having a boy or girl.
The Ericsson method involves collecting sperm from the male partner and sorting it in a lab environment. The sperm is sorted by measuring the speed with which it swims through multiple layers of albumin (a blood component). There have been no large scale, controlled medical trials involving the Ericsson method. Samples tested using this selection technique have consistently been shown to still have a 1:1 ratio of X and Y carrying sperm.
Microsort is advertised as aiding gender selection by sorting sperm in a centrifuge to separate it into X and Y components based on minute differences in molecular weight. An FDA trial of this method was discontinued prematurely and is not approved for use in general fertility treatment. Initial results for this technique have not yet been replicated in large, multi-center trials.
Currently, preimplantation genetic diagnosis (PGD) is the only proven method of gender selection. This approach involves safely removing cells from a 5 day old embryo during an In Vitro Fertilization cycle. PGD sex selection is over 99% accurate. This test leaves the rest of the embryo intact to develop normally.