Pregnant women should eat fish weekly to raise baby's birth weight, says study

Pregnant women who eat fish once a week reduce the risk of a premature birth or having an underweight baby, a new study suggests.

Women who seldom or never eat fish are three times more likely to have a pre-term delivery or a baby with a low birth weight, the research published in today's British Medical Journal indicates.

The Danish study, which monitored 8,700 pregnant women, concluded that even a small weekly intake of fish or fish oil supplements during early pregnancy could increase birth weight and prolong the period of gestation.

A higher intake of fish – the equivalent of 15g a day or about 4oz a week – increased the chance of a full-term pregnancy or average birth-weight baby.

Doctors from Skejby University Hospital, in Aarhus, asked women receiving ante-natal care to record how much fish they ate from the 16th to the 30th week of pregnancy. The fish could be in hot meals, salads or sandwiches.

The occurrence of premature delivery fell from 7.1 per cent in women who had not eaten fish to only 1.9 per cent in those who ate fish at least once a week. The protective effect rose as women ate more fish, up to the equivalent of 15g a day.

Dr Sjurour Frooi Olsen, of the Maternal Nutrition Group at the Danish Epidemiology Science Centre, Copenhagen, said: "For women with zero or low fish intake, small amounts of omega-3 fatty acids provided as fish or fish oil may confer protection against pre-term delivery and low birth weight."

Dr Olsen added that a low intake of the fatty acids found in fish may result in higher levels of prostaglandins, the hormones that trigger labour.

WellBeing, the research arm of the Royal College of Obstetricians and Gynaecologists, said the findings could have implications for the 70,000 British women who gave birth prematurely each year.

Professor David Taylor, of WellBeing's research advisory committee, said: "Lifestyle factors, such as nutrition, are recognised to play a role in the causation of pre-term birth and this Danish group has focused on the role of fish in the diet. This study ... should be a stimulus for research in populations other than Denmark."

A second study in the British Medical Journal found that "denied pregnancies" – where a woman has not acknowledged or has been unaware she is carrying a child – were not that rare, occurring once in every 475 pregnancies. Of the 62 cases surveyed in which women did not recognise they were pregnant until after 20 weeks, 12 admitted not realising until they went into labour.