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Holly Willoughby has said that she chose not to find out the sex of her third baby because she already has 'one of each' (five-year-old son Harry and daughter Belle, three). But not everyone achieves the same balance - dad of three boys Bear Grylls has spoken of his desire to add a girl to the family.
So, is it ever possible to influence the sex of your baby? From eating more cheese to buying your partner tighter pants, we investigate the methods that can, supposedly, help you do so...
Timing is everything
Some scientists believe your chances of having a particular sex is influenced by when and how often you make love.
In his book, 'How to Choose the Sex of Your Baby', Dr Landrum Shettles claims you can choose your baby's gender by having sex on certain days of your cycle.
To boost your chances of conceiving a girl, you need to have sex two to three days before ovulation, as female sperm have more staying power. To increase your chances of having a boy, it's best to have sex as close to ovulation as possible because the Y-sperm is faster and gets to the egg first.
Although there's no strong scientific evidence to support Shettles' claims, proponents claim the technique is 75% effective. However other experts dispute this and a recent computer analysis of sperm failed to find the supposed differences between male and female sperm.
The Whelan method directly contradicts the Shettles method. The theory here is that biochemical changes that may favour boy-producing sperm occur earlier in a woman's cycle.
So if you want a boy, you should have intercourse four to six days before your basal body temperature - your temperature when you wake up - goes up; or two to three days before you ovulate for a girl.
The Whelan method is claimed to be 68 per cent effective for boys and 56 per cent for girls but again this is disputed.
If you want to try either technique it's important to know when you're ovulating, so you'll need to keep a temperature chart (your temperature goes up on ovulation) or use an ovulation test kit.
Start the day right
Skipping breakfast reduces blood glucose levels and it's known from IVF research that high levels of glucose encourage the growth and development of male embryos over female ones. (Although a balanced diet is obviously best to aid conception.)
Watch your calorie intake
A study of 740 women found those who ate a high-calorie diet around the time they were ovulating were 10 per cent more likely to have a boy.
The researchers also reckon the trend for lower-calorie diets may explain why, over the past 40 years, there's been a slow but consistent decline of around one boy per 1,000 births every year.
Go bananas for boys
A study from the Netherlands found women who had diets with high levels of sodium and potassium (bananas and tomatoes) made conceiving a boy more likely. Want a girl? The same study found women who cut out salty foods and consumed lots of calcium and magnesium (beans and nuts) were 80 percent more likely to have girl.
If you're going to give it a try make sure you don't exceed 6g a day of salt and avoid obesity or eating too little – both can have lifelong health consequences for your child.
Keep cool for a girl
Some say a man's testicles should be cool before sex if you want a daughter so choose boxers over tighty-whiteys; for a son, go for the latter. And you need to keep your cool too - according to some, being relaxed when you conceive means you'll have a girl whereas if you're a worrier, you should start buying blue babygros.
Get in the right position
The ancient Greeks believed men who had sex while lying on their right side were more likely to have a son, while Italian folklore says the missionary position is best for a girl.
They might have been on to something too - female sperm cope better than male sperm with the acid environment lower down the vagina so the missionary position is said to work a treat.
For a boy, deep penetration could boost your chances. This deposits sperm near the opening of the cervix which favours fast-moving male sperm.
Spring for a girl, autumn for a boy
In Western Europe, statistics show April's the best month for conceiving a girl, while October and November bring forth boys. Nature's way of giving boys a helping hand? Baby boys tend to be weaker than girls and more vulnerable to illness so this way they'll be born before the bitter winter months...
'Oh, oh, oh!' for a boy
Go for the big-O if you want a boy as it's been claimed the body produces chemicals after orgasm that make the vaginal environment more alkaline, favouring Y-sperm. Also, when a woman reaches orgasm, contractions of the womb draw sperm towards the cervix, giving faster male sperm a boost.
As you can see, these are some interesting ideas, but the important thing is that your baby and you are happy and healthy.
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