Dieting women who get pregnant put their babies at risk, says expert

Women who diet could be harming their baby when they get pregnant, an Auckland expert in fetal development says.

"How the baby is looked after from the moment of conception, when it's just one egg, to birth [and] in the neo-natal period can affect its destiny for the rest of its life," Professor Peter Gluckman, director of the Liggins Institute at Auckland University, said.

It was too late for a woman to stop dieting by the time she realised she was pregnant because fetal development started from day one, he told the Channelnewsasia website.

He said the problem of dieting mums-to-be was especially worrying in Asia: a Japanese study had shown that newborn babies were now 150g to 200g lighter than 10 years ago, because their mothers were dieting.

During each pregnancy, expectant mothers should ideally gain about 10kg, he said.

"The foetus is preparing for its life after birth so everything that the mother does sends signals to the foetus, which tell the foetus about the world out there," Professor Gluckman said.

Women who were dieting or otherwise undernourished would have smaller babies which might suffer from health problems later in life.

"Small babies are more likely to get obese because what they did is to prepare themselves inside the womb for a world without much food," he said.

Such nutritional signals, especially in early pregnancy, would turn some genetic switches on or off for the rest of the child's life.

These would make the child more prone to storing fat so as to prepare itself for the signalled threats in the outside world.

Women who only started taking care of their nutrition when they found they were pregnant might be too late in reversing the genetic switching, studies had shown.

Compounded with a high-fat diet and sedentary lifestyle, these children were even more likely to become obese - a cause of diabetes and cardiovascular disease later in life.

Smaller babies also had fewer brain cells, particularly those needed for memory and learning.

Similarly, women should not smoke during their pregnancy as this would alter the child's lung development, among other things, which would change physically to adapt to a perceived world filled with carbon monoxide.

Professor Gluckman, who chairs the World Health Organisation technical committee on getting the best available outcomes from pregnancy, said women should have a balanced diet and maintain a reasonable body mass index.

They should not get pregnant in the four to five years after their first period as they still needed nutrients for growing, and when the baby was born, breastfeeding was recommended until the baby was six months old.

Parental involvement and stimulation in the first year of the child was important, as was the intake of vitamin B12 and folate.

Stress would not affect the fetus unless it was severe, such as the effects of a natural catastrophe, he said.

In New Zealand, draft food and nutrition guidelines just released by the Health Ministry said the nutritional content of a pregnant woman's diet was critical.

"Women who eat energy-dense nutrient-poor junk food may gain adequate or excessive weight but may have compromised nutritional intake and be at increased risk for an adverse pregnancy outcome," the guidelines said.

- NZPA