As scientists link a high-fat diet with ADHD, Chloe Lambert reports on the latest advice for expectant mothers
No sooner does a woman break the news that she is pregnant than she is bombarded with a list of things she must eat or avoid, from alcohol to sushi, blue cheese to Parma ham. The advice is ever changing and still controversial. But what’s becoming clear is just how crucial a woman’s diet is to her child’s future health.
Last month, scientists from King’s College London and the University of Bristol reported that a high-fat, high-sugar diet during pregnancy could alter a growing foetus’s DNA, leading to brain changes that raise the risk of attention deficit hyperactivity disorder (ADHD). Here, experts explain the latest thinking on what to eat in pregnancy.
How children’s tastes are set in the womb
At five months, a foetus begins to recognise flavours in the amniotic fluid from the food and drink their mother is consuming. Scientists now believe that the tastes that babies are exposed to in the womb can determine the foods they prefer in later life. In one study, women who drank carrot juice during the last trimester had babies who responded more positively to carrot flavours during weaning. Conversely, animal studies suggest that mothers who eat junk food – fatty, sugary, processed foods and drinks – during pregnancy and breastfeeding have children who prefer these foods.
“Following a healthy, balanced diet isn’t just good for you and your baby’s health – early research suggests maternal diet in pregnancy could have both a positive and negative influence on your child’s taste preferences,” spokeswoman for the British Dietetic Association Sian Porter says.
And while all pregnant women should take vitamin D throughout pregnancy, and folic acid during the first 12 weeks, Porter says it’s better to get vitamins and nutrients from food.
Recently, a review in the journal Drug and Therapeutics Bulletin said multivitamin supplements marketed to pregnant women were “an unnecessary expense”.
Researchers found no evidence to recommend supplementation during pregnancy beyond folic acid and vitamin D.
The myth of eating for two
“You shouldn’t really try to lose weight while you’re pregnant, but it’s important not to eat too much, too,” says Porter. “Normal weight gain for women is about 12kg during pregnancy, but most of that should come from the baby.”
Gaining excessive weight during pregnancy raises the risk of complications such as pre-eclampsia and gestational diabetes, and the need for a caesarean section. Government advice states that pregnant women need to eat only an extra 200 calories per day in the last trimester.
Salmon is in, but sushi is out
A series of studies has shown that oily fish, such as salmon and mackerel, is beneficial in pregnancy: one recent trial by the University of Southampton found that children born to women who regularly ate salmon during pregnancy were less likely to develop asthma.
However, mothers-to-be should limit the amount of oily fish they eat to two portions a week, because it contains pollutants that can harm the development of a foetus.
Some fish, including shark, swordfish and marlin, should be avoided completely because they contain high levels of mercury.
Confusingly, though, sushi is to be avoided during pregnancy, because raw fish, including salmon, can carry small parasitic worms that can cause infection. “We advise avoiding sushi completely. If somewhere along the line the fish has been frozen for at least 24 hours, then the risk is minimal,” Dr O’Brien says.
“I suspect most high-street places will freeze it, but they may not declare it, and if you’re not sure, it’s not a difficult thing to cut out while pregnant to be on the safe side.”
Smoked salmon, on the other hand, is generally considered safe.
A last word on alcohol
Alcohol during pregnancy, particularly in the first 12 weeks, has been linked to miscarriage and an increased risk of premature birth and low birth weight.
Government advice is to avoid alcohol – which concurs with advice in many other countries, including the United States and France – and if you do decide to drink, to consume no more than one to two units once or twice a week.
Not only is exercise safe in pregnancy, it’s also excellent for the health of mother and baby, protecting against depression, weight gain and diabetes, and improving strength and stability, which helps to prevent common problems such as back pain. Yet women are often left confused about what they should do, says Professor Greg Whyte, an expert in sports science.
“There is so much misinformation. I’ve even spoken to women who were told by their midwife to do no exercise in the first trimester. Invariably that’s going to be more damaging.” He says two of the biggest misconceptions are that exercise can trigger a premature birth, or that it reduces oxygen supply to the baby.
Professor Whyte says that in our modern, sedentary culture, pregnant women should be given recommendations on exercise by health professionals in the same way as they are about diet and issues such as avoiding alcohol.
“If you’re someone who already exercises regularly, in the vast majority of pregnancies there should be no reason why you can’t carry on doing it right through the pregnancy.
“Just remember that, unlike a normal exercise plan, where you work harder and harder over time, in pregnancy you need to gradually reduce the intensity and go easier as things progress.”
If you’re pregnant and new to exercise, he adds, “start very easily and progress slowly”. Whatever your exercise, whether it’s running, swimming or weightlifting, it’s important to work at, or below, a moderate intensity to avoid overheating, dehydration and injury. – The Daily Telegraph