The late Dr. Landrum Shettles developed a baby gender selection method that he felt was "best supported by scientific evidence."
He wrote a million copy best selling book explaining his methods called How To Choose The Sex Of Your Baby which you will find a link to by visiting my website below. Dr Shettles claims a 75%-90% success rate using his simple, all natural, at home methods, and many thousands of couples have enjoyed an even higher (up to 98%) success rate using these very same methods to help them choose to have the baby boy or girl they wanted.
The Shettles method is based on the fact that it's the man's sperm that determines whether a baby is a female or male. This is because the woman's egg carries only the (x) or (girl) chromosome, and the man's sperm comes in two varieties, one carrying the (x) or girl sperm (which results in a girl baby) and the (y) or boy sperm (that results in a boy baby.) Dr Shettles also realized that the girl sperm was physically larger, stronger (longer lived), and a slower swimmer (slower to reach the egg.) The boy sperm is smaller, more fragile (dies off quicker), and is a much faster swimmer (will win the race to fertilize the egg most of the time.)
The doctor also realized that timing of intercourse, and the depth of penetration during conceptual intercourse could help to determine if the resulting baby was a boy or girl. To mother-to-be will have to track her day of ovulation precisely in order to time conceptual intercourse precisely as well.
If a boy baby is desired abstain from sex until the day before ovulation, and abstain again the second day after ovulation. Also when trying to conceive a boy sexual positions that allow deep penetration are best ("doggie style" or missionary position with the woman's legs extended up towards her head.) Why is this? Because of the differences in the two sperm. This timing, and deep penetration allows the fast swimming boy sperm to win the race to the fresh waiting egg, resulting in the boy baby you want.
If a girl baby is desired, the couple should have sex practicing only shallow penetration, and abstain from sex for a couple of days before ovulation and until a couple of days after ovulation. Here again this gives the short lived boy sperm to much time and distance to survive and allows the slow but longer lived girl sperm a time and distance advantage, and assures (hopefully) conceiving a girl baby.
Dr Shettles determined that vaginal acidity also plays a role in which sperm succeeds in fertilizing the egg. He found that a lower ph (higher acidity) favored the girl sperm and a higher ph (lower acidity) favored the survival of the boy sperm.
Although these are pretty simple concepts, you will find a guide to be indispensable! There are three ebooks offered online that will take you step by step through the entire process, and if followed diligently tip the odds of success from about 50/50 to well over 90%!
If you are serious about choosing the gender of your next baby to complete your family, spend the money it would cost you for a night out for a pizza, pick up Rebecca Washburn's eBook and give yourself the best chance to choose whether you conceive a baby girl or boy.