Between 70 and 80 per cent of pregnant women suffer from morning sickness, yet it is still not known exactly why. One theory is that it is caused by the high levels of certain hormones, especially BhCG and progesterone. The latter relaxes smooth muscles, including those of the digestive tract, and this results in food taking longer to pass through the stomach and intestines. Another theory is that it tends to occur at the times of the day when women might have low blood sugar and/or are tired, such as first thing in the morning or in the late afternoon.

Finally, some people think that it is nature's way of making women avoid certain foods and liquids that could be harmful to the developing fetus at what is a developmentally crucial time. But this, too, cannot be proved, particularly since not all women suffer from morning sickness; and of those that do, there is such a wide range of foods that they go off completely that it is impossible to make any sort of firm link.

There are a several myths surrounding morning sickness, none of which is based on scientific evidence.

One is that suffering from morning sickness is a sign of a healthy pregnancy and a healthy fetus. This is absolutely not the case and there is no link at all between a lack of symptoms and a higher rate of miscarriage. Another is that you will have a boy or a girl depending on whether or not you suffer from morning sickness. Again, this is totally without foundation.

Tips for alleviating morning sickness:

The following advice has come about as a result of dealing with pregnant women over many years who are suffering from morning sickness. They may not work for everyone, but could nonetheless be worth a try:

  • Eat small amounts every one or two hours to limit the build-up of stomach acid.
  • Aim for small, easy-to-digest meals, or even tablespoon-sized portions.
  • Stick to bland, starchy foods, such as toast, plain pasta or plain biscuits.
  • Place a bland snack (eg plain biscuits, oatcakes) by your bedside at night, so that you can nibble on it first thing if your nausea is worse in the morning.
  • Boost your diet with plain, non-sugary cereals, such as cornflakes with skimmed (ie non-fat) milk, as many cereals are fortified with vitamins and minerals and the milk contains important calcium.
  • Avoid rich, fatty or spicy foods.
  • Avoid acidic drinks, such as fruit juices, and drink water and herbal teas (eg peppermint, camomile) instead.
  • Wear acupressure wrist bands (sold in pharmacies to prevent motion sickness); these should be worn at all times and preferably until you are about 16 weeks pregnant for best effect.
  • Take ginger (a known remedy for nausea) in tablet or capsule form (ginger flavoured biscuits or tea do not have enough concentration to make a difference).
  • Keep away from kitchen smells and avoid cooking, if possible, until your morning sickness improves.
  • Rest as much as you can (ask family/friends to help, especially if you have small children).
  • This is an edited extract from One Born Every Minute: Expecting a Baby? by Dr Penelope Law (Quadrille, £25).Text © 2013 Dr Penelope Law