More than twenty years ago, a physician by the name of Landrum Shettles devised a method for gender selection. The basis of his theory is that the sperm that carries the X chromosome, needed for conception of a girl, swims slower and lives longer than the sperm that carries the Y chromosome, necessary to conceive a boy. So if a baby boy is desired, the couple should have sexual intercourse as close as possible to ovulation. If a baby girl is desired, the couple should perform sexual intercourse 3-5 days before ovulation and then abstain from sex. This will allow the faster but weaker Y male sperm to die off before the ovum is available for fertilisation, thus leaving the path clear for the longer lasting X female sperm to fertilise the ovum as soon as it arrives.

Yet another natural method is based on where the sperms are deposited. Shallow penetration results in the sperms to be deposited at the mouth of the cervix. Here the environment is acidic which is hostile to the Y male sperm. Avoid orgasm in order to maintain the acidic nature of the vaginal environment and you improve the chances of getting a baby girl. Use deep penetration to deposit the sperm above the neck of the cervix where the environment is more alkaline, making it easier for the Y male sperm to survive. Try to achieve orgasm to help foster a more alkaline environment which favors the Y male sperms in order to get a baby boy.

Due to their different characteristics, the X and Y bearing chromosome can be sorted to a certain degree and harvested. This separation of the sperms is done in the laboratory.

In the Ericson method, the semen is laid over albumin solutions. The Y male sperms swim faster and a harvest from the bottom column would yield a high percentage of Y male sperms.

In another procedure, called the Percoll method, the semen is placed in a test tube and spun through a chemical solution of different concentrations. The denser and heavier X female sperm would be spun to the bottom of the tube which would have a high percentage of X female sperms.

One of the latest techniques used to sort Y male sperms from X female sperms is Cytometric Separation Technology. A dye is used to stain the DNA in the sperms.

The harvested X female or Y male sperm bearing fractions from the above laboratory techniques are then implanted into the woman's uterus in a procedure called artificial insemination which is performed close to ovulation. The success rate in most of these techniques is 55-65%.

There is a process called IVF (in vitro fertilisation) where drugs are given to a woman to simulate her ovary to produce more ova (eggs). The mature ova are removed and fertilised by a sperm outside her body. Once the embryo has reached the 8-cell stage, one of the cells is teased off from the embryo (without damaging it) and tested for the presence or absence of the Y male chromosome. The embryo is then inserted back into the woman's uterus. This technique is suitable for couples where the husband's sperms are normal but the woman's fallopian tubes are blocked. Although the success rate for gender selection is 100%, the pregnancy rate is only 15-25%.

In the ICSI (Intra Cytoplamic Sperm Injection) procedure, a single sperm is injected directly into an ovum after micro-sorting the semen using electrophoreses and the fertilised ovum is implanted back into the Uterus. This techinique is suitable fo rmen with very low sperm count, poor motility or a high number of abnormal sperms. The pregnancy rate varies from 21-41%.