Conceiving is all about having sex at the right time this week, but if you're hoping to have a child of a specific gender, the timing could be even more important. Some experts claim there is a link between when you have sex and the baby's gender.

Recent research suggests that women who have a high calorie intake (especially if they eat that most phallic of fruit, the banana) are marginally more likely to bear a boy. Those who skip breakfast or have a low calorie intake are more likely to have a girl. One reason for this is thought to be that the extra calories consumed affect vaginal secretions and help to give the Y sperm that makes baby boys a vital boost.

The Shettles method, devised by Dr. Landrum Shettles, is based on the fact that Y sperm (for boys) are smaller, faster, and less resilient than X sperm (for girls), and are less able to withstand an acidic environment in the vagina.

The Whelan method, devised by Dr. Elizabeth Whelan, suggests that having sex earlier on in the cycle, some four to six days before ovulation, is more likely to result in a boy. Sex nearer the time of ovulation is more likely to result in a girl. Curiously, the Whelan way is more or less the opposite of the advice given by Shettles.

But what works? The mainstream medical view, supported by reports in journals such as the New England Journal of Medicine, is that the timing of sex has little or no bearing on gender. The possible exception is that having sex two days before ovulation may be slightly more likely to favor a girl.

If you already have two same-sex children, you're 75 percent more likely to conceive a child of that sex again.

Although the sex of the baby conceived is random, conceiving children of the same sex could be due to the fact that some men produce better quality X sperm, which makes baby girls, or Y sperm, which makes baby boys.

Statistically, couples who have two children of different sexes are less likely to try for a third child.