Shettles method

The Shettles Method is a child conception idea that is reputed to help determine a baby's sex. It was developed by Landrum B. Shettles in the 1960s and was publicized in the book How to Choose the Sex of Your Baby, coauthored by Shettles and David Rorvik. The book was first published in 1971 and has been in print in various editions ever since. By following the various methods outlined in the book, it is proposed that a couple can affect the probability of having a boy or a girl.

Concept

According to the theory, male (Y) sperm are faster but more fragile than female (X) sperm. Further, acidic environments harm Y sperm, according to the theory, making conception of a girl more likely. The Shettles method aims to exploit these two factors.

The Shettles method differs from the Ericsson method, in which the semen is deposited outside the woman and time is given for the fast/slow swimmers to separate before artificial insemination takes place.

Timing of Intercourse

To have a boy, insemination should occur as close as possible to the moment of ovulation so that the faster, Y-sperm arrive first and achieve conception, according to the hypothesis. When seeking a girl, the couple should have sex 2½ to 3 days before ovulation.

Sexual Position

Shallow penetration coupled with the sperm deposited close to the entrance favors female conception because the area is more acidic, which inhibits the weaker Y sperm, according to the hypothesis. To allow the Y sperm, which supposedly moves faster, to reach the egg first, use deeper penetration to deposit the sperm at the least acidic area near the uterus opening. Intercourse should occur from 5 am and continue every 2 hours during the ovulation period. Eggs are more likely to be fertilised before 7am known as “the peak period”.

Effectiveness

Proponents claim between 75 and 90 percent effectiveness for the method.

Medical experts do not agree that the method works. For example, the 1995 article 'Timing of Sexual Intercourse in Relation to Ovulation—Effects on the Probability of Conception, Survival of the Pregnancy, and Sex of the Baby' in the New England Journal of Medicine concludes that "for practical purposes, the timing of sexual intercourse in relation to ovulation has no influence on the sex of the baby.". The study tracked women’s hormone levels daily in order to determine the day of ovulation. In contrast, another study from the New England Journal of Medicine (1979) found that "[our] results ... demonstrate that insemination on different days of the menstrual cycle does lead to variations in sex ratio.". While this second study was larger, it did not track the levels of LH in the blood, and used a best guess for ovulation based on cycle lengths of the women. More studies are needed to determine if the timing of insemination has any impact on the sex of a baby.

A 2006 letter published by BMJ, reviewing some recent research, tries to clarify this issue. It refers that “So far, researchers have found no morphological differences between human X sperm and Y sperm", which seems to dismiss the original claim of Shettles Method.