The Shettles Method is a child conception

Fertilisation

Fertilisation is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo...

 idea that is reputed to help determine a baby's

Infant

A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...

 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

David Rorvik

David Michael Rorvik is an American journalist and novelist who was the author of the 1978 book In his Image: The Cloning of a Man in which he claimed to have been part of a successful endeavor to create a clone of a human being....

. 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. Proponents claim between 75 and 90 percent effectiveness, but 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

New England Journal of Medicine

The New England Journal of Medicine is an English-language peer-reviewed medical journal published by the Massachusetts Medical Society. It describes itself as the oldest continuously published medical journal in the world.-History:...

concludes that "for practical purposes, the timing of sexual intercourse in relation to ovulation has no influence on the sex of the baby."

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

Ericsson method

The Ericsson Method is a child conception idea that is reputed to help determine a baby's sex, developed and patented by Dr. Ronald Ericsson. The method has been in use since the mid 1970s. Dr...

, in which the semen is deposited outside the woman and time is given for the fast/slow swimmers to separate before artificial insemination

Artificial insemination

Artificial insemination, or AI, is the process by which sperm is placed into the reproductive tract of a female for the purpose of impregnating the female by using means other than sexual intercourse or natural insemination...

 takes place.

Timing of Intercourse

In order 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 theory. When seeking a girl insemination the couple should seek to 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 theory. To allow the Y sperm to reach the egg first (which supposedly moves at a faster rate), deeper penetration should be sought, to deposit the sperm at the least acidic area near the uterus opening.

Orgasms

Female Orgasm

Orgasm

Orgasm is the peak of the plateau phase of the sexual response cycle, characterized by an intense sensation of pleasure...

favors male sperm because they make the vaginal environment more alkaline.