Medical science proves beyond doubt that a baby's gender is determined by the father. So why is the idea of natural gender selection gaining ground? Rosalind Scutt investigates.

According to mainstream medicine, defining baby's gender is simple: at the moment of ejaculation the male releases a collective of individual sperm (some male, some female). If one of those sperm finds its way successfully to the egg (the egg is neutral, being neither male nor female) and circumstances are favourable, that fertilised egg will develop into a foetus and eventually a baby.

Whether you get a boy or a girl depends entirely on which type of sperm meets the egg first (a male sperm is programmed with the XY chromosomes and a female sperm is programmed with XX chromosomes).

Since women carry XX chromosomes and men carry XY chromosomes, it follows that the man is always responsible for baby's gender. Regardless of the many old wives' tales, the fact remains that the man is the only possible carrier of the Y chromosome and therefore the only participant capable of providing a directive with XY chromosomes).

However, contrary to this is a rapidly growing idea that a couple can increase their chances of conceiving a particular gender by manipulating two main factors: body chemistry and the time of intercourse.

Though unproven, some believe that the manipulation of body chemistry with diet and exercise (and other factors like wearing loose knickers to keep sperm cool) can skew the environment to better favour a particular sperm (male or female).

So, how can you attempt to influence the gender of your baby?

Method one: By manipulating body chemistry (acid/alkaline levels)

A woman's monthly bodily cycle includes alternating pH levels (acidic and alkaline) within her reproductive tract. The changes in the pH environment within is now thought to affect baby's gender. Experts say that alkaline in the follicular fluid will favour Y sperm (conceive a boy) while acidic in the follicular fluid gives preference to the X sperm (conceive a girl).

To conceive a girl you should:

• Eat a diet higher in magnesium, calcium and acidic foods such as corn, meat, beans, fish, plums, coffee, eggs, liver and yogurt.
• Avoid alkaline foods such as bananas, orange, potatoes and watermelon.
• Take supplements such as calcium, folic acid, magnesium and vitamin C to help make the cervical mucus acidic (which will in turn kill the Y sperm).

To conceive a boy you should:

• Avoid dairy products and lower magnesium and calcium supplements
• Increase vegetables and fresh fruits
• Increase foods that contain potassium, like bananas
• Eat plenty of alkalinising foods including figs, cherries, fresh lemons, spelt bread, lentils, avocado, royal jelly, pine nuts, almonds, carrots, red radish, fresh red beets, alfalfa grass, barley grass, sprouted seeds, and wheatgrass.
• The father should also avoid excess heating around the genitals because heat destroys male sperm faster than female ones (also, avoid tight-fitting underwear, saunas, hot tubs etc)

Source for diet information referenced above: www.newbornbaby.com.au

Method two: Manipulate the time of intercourse

According to the well-known theory developed by Dr Shettles (known as The Shettles Theory), sperm with the Y chromosome (boy sperm) travel faster and have a shorter life span than sperm with X chromosome (girl sperm).

The theory says that having sex two to three days prior to ovulation means that by the time of ovulation, the boy sperms will have died off leaving only the girls sperms and hence, a greater likelihood of conceiving a girl.

Shettles theory says that by having sex closer to ovulation you will decrease your probability of conceiving a girl and increase the probability of conceiving a boy.

Method three: Sexual position

The depth of penetration during intercourse will affect where the sperm will be deposited in the vagina. This could be important for two reasons: the distance to the egg and the pH level where the sperm are first placed may give an advantage to one of the sperms types (X or Y).

For a girl, shallow penetration means the sperm will be deposited nearer the entrance of the vagina where the vagina is more acidic. It is thought that the acidity here holds back the weaker boy sperm (the tough girl sperm can survive). Further, this location favours the slower girl sperms because although the boy sperms are faster, they cannot maintain pace all the way to the egg (girl sperm is slower but can go the distance).

To conceive a boy, try depositing sperm closer to the cervix opening which may give the more aggressive and quicker moving "boy" sperm a head start.To do this try deep penetration, preferably with the "doggy style" position. Also, the opening of the cervix is less acidic and more alkaline favouring the survival of boy sperm.

A word of caution:

So far, the ideas above remain unproven although there are is a growing number of followers who claim success by these methods (including Terri and the late Steve Irwin who conceived a boy, apparently after Terri ate foods high in salt and potassium while Steve took to wearing boxer shorts to help keep the male sperm cool).

Confused? Go ahead and try your luck! While medical research has noted a slight decrease in the birth of boys born in western countries over the past few decades, science still maintains your odds are very close to 50/50.

Good luck!

Tell us about your best tips for conceiving for your chance to win $200! Enter here