Life is tough enough without having someone kick you from the inside.
There is very little reliable evidence that you can have any effect on the sex of your future children. One study of 700 pregnant women found that women who ate at least one bowl of breakfast cereal daily were 87% more likely to have boys than those who ate no more than one bowl per week. Women who had boys also ate about 400 calories more daily than those who had girls, on average. However, these results have since been highly criticised.
The only certain way to ensure a certain sex is embryo selection through in vitro fertilisation. In America and Thailand there are clinics that offer the option of choosing your child’s sex, although the process is not easy or cheap (it costs around $18,000).
Aristotle (384 bc-322 bc) thought the diet of the mother and the sexual position used at conception made a difference. Anaxagoras (c. 500 bc–428 bc) thought boys and girls came out of different testicles and recommended tying off the undesirable one before sex. Hippocrates (c. 460 bc–c.370 bc) thought that the male foetus comes from the right ovary and the female from the left.
Aristotle believed hares could get pregnant while they were already pregnant. This has been controversial for two millennia, but he was finally proved right in a study of European brown hares by the Leibniz Institute for Zoo and Wildlife Research in Berlin, published in Nature in 2010. Male hares can fertilise females even when they're heavily pregnant. The new embryo develops four days before the first baby hare is born. Because the uterus is already full, the new embryo waits in the oviduct till ready. It's an evolutionary trick to shorten the time between litters and so produce more babies. Hares are also known as jackrabbits, particularly in America.
This process, known as superconception or superfetation, occurs when two eggs are fertilised during different menstrual cycles. It happens most often among hares, but can also occur (though much more rarely) among badgers, American minks, panthers, buffalos and swamp wallabies. It can only take place if ovulation continues throughout pregnancy, something that normally doesn’t happen. There's a similar trick called superfecundation, which involves two different ova being fertilised during the same cycle.
Aristotle also thought it was possible for humans, and (despite much scoffing over the years) it appears he was right about that, too. In 2010, an Arkansas woman gave birth to twins conceived two weeks apart. This means that two children sharing the same womb could have different fathers.
People are giving birth underwater now. They say it's less traumatic for the baby because it's in water. But certainly more traumatic for the other people in the pool.
Pregnancy cravings are very mysterious – they might be either a response to mineral deficiencies, an instinctive effort to protect against illness, or largely psychological; the evidence is inconclusive.
Craving non-food substances during pregnancy is called 'pica'. A third of cravings these days aren't for food, which suggests that cravings might be to do with texture and smell rather than taste. Cravings vary around the world: almost no Danish women eat clay or earth during pregnancy but in coastal Kenya 56% of women do. In Malawi a woman observed eating clay is assumed to be pregnant – that's how you 'know'. Geophagic (earth-eating) clay is sold in American shops. It's not bad for you – the only risk is the chance of constipation.
Despite the common claim of ‘eating for two’, women need very few extra calories during pregnancy. Mothers-to-be don't need to change their diet at all for the first six months, and even in the last three they need just 200 extra calories a day, the equivalent of a small sandwich.