In the dark: what pregnant women should know – but don't

According to a survey, expectant mothers are confused about what they should and shouldn't do, and too embarrassed to ask for advice. Health Editor Jeremy Laurance has the answers

Having a baby ought to be the most natural experience in the world – but for many women it is a part of their life marked by confusion and embarrassment.

A survey by the baby charity Tommy's has found almost half of the women asked said they received conflicting information about their pregnancy that left them unclear what they should and should not do.

The confusion extended to what they should eat and drink, whether they could continue having sex, fly in an aeroplane or dye their hair. One in three women also experienced unexpected physical changes, ranging from bladder weakness to mood swings and memory loss, but half of those affected felt too embarrassed to share their experience with anyone.

Jenny Carter, a Tommy's research midwife, said the survey of 1,300 women, conducted with Johnson's Baby, revealed the difficulties women had in obtaining consistent advice during pregnancy, even from professionals.

"The National Institute of Clinical Excellence (Nice) has issued guidelines to ensure we are all singing from the same hymn sheet," she said. "But women also get advice from their friends and families that can be out of date."

What is safe to eat?

One of the commonest areas of confusion is diet. Women's taste buds become more sensitive during pregnancy and many develop cravings for particular foods, including in rare cases items such as chalk and coal.

Official advice is to avoid foods that are undercooked or uncooked, including soft boiled eggs, rare steaks and Parma ham (which is cured, not cooked) to reduce the risk of food poisoning. Women are told fatty acids are good in pregnancy but many get them from cod liver oil, which contains potentially harmfully high levels of vitamin A. Liver and liver products should be avoided. Certain fish, including swordfish, shark and marlin should also be off the menu because of their tendency to absorb mercury from the sea. Tuna should be restricted to one fresh steak or two tins a week, for the same reason.

How much alcohol can you drink?

Not even the experts have been able to agree on this. Nice said the first three months should be teetotal but one to two drinks a day was safe thereafter in guidance issued last March. That clashed with advice from the Department of Health last year which said there was no safe limit throughout pregnancy.

Tommy's advice is that alcohol is best avoided altogether, on the ground that the risks of heavy drinking during pregnancy are well known: an increased incidence of miscarriage and low birth weight. "But if you have the odd glass of wine it is unlikely to cause a problem," said Ms Carter. "It is just that we can't say for sure because we don't have the evidence."

Is it OK to have sex during pregnancy?

The myth that having sex may in some way damage the developing baby is widespread. But Ms Carter was emphatic. "There is absolutely nothing wrong with having sex during pregnancy. Some women may feel more sexy and some less – libido can change. Often in the early months when women feel tired and sick they are less interested in sex. But the basic message is it is absolutely fine – there should be no confusion about that."

Is it safe to dye your hair?

The skin can become more sensitive in some women during pregnancy, making them more prone to allergic reactions. It is wise to test the dye on a small patch of skin first. There is no evidence that it poses a risk to the baby but equally it is impossible to say it is totally safe.

Ms Carter said: "If you really want to do it, it is probably OK, but test it first. You could have an allergic reaction and you don't want to end up with a big red patch. To reduce exposure to the chemicals it is probably best to get someone else to do it."

Is it OK to travel by plane?

It is safe to fly but there is an increased risk of deep-vein thrombosis in pregnancy. Tommy's advises wearing special socks on long-haul flights and moving about to prevent DVT. Some airlines require a letter from a GP for women more than 28 weeks pregnant, others require it for flyers over 36 weeks.