'Seasonal link' to birth problems

Women who give birth in winter run a greater risk of suffering a potentially fatal complication of pregnancy, new research reveals.

Women who give birth in winter run a greater risk of suffering a potentially fatal complication of pregnancy, new research reveals.

The condition, which is known as pre-eclampsia, is the result of a defect in the placenta, which joins mother and baby. It occurs in about 10 per cent of pregnancies, and in severe cases it can threaten the life of both the mother and her unborn child during labour.

Little is known about its causes. But a study of 1.9 million births in Norway, which is published in the British Journal of Obstetrics and Gynaecology today, has found a strong seasonal pattern.

The condition, which is symptomless in its early stages and detectable only by checks of the mother's blood pressure and urine, peaks among births during the winter months and falls to a low in the summer.

Most common among babies born in November and December, it declines in prevalence in late spring and is least common among August births.

The authors suggest that environmental factors in early pregnancy, such as cold weather, infections or diet, may account for the winter peak.

Professor Per Magnus, of the National Institute of Public Health in Oslo, says that seasonal trends have also been observed elsewhere in the world.

In Ghana and Zimbabwe more cases occur in the rainy season, in Singapore it is twice as common in the hot, dry months of February, March and April, and in Kuwait it is most prevalent in November, a month of low temperatures and high humidity.

He suggests that cold weather in the first few weeks of pregnancy could affect the blood flow, and infections and dietary deficiencies in early pregnancy could predispose women to pre-eclampsia.

The condition kills 500 to 600 babies in the UK and up to 10 mothers each year. Most women do not feel ill in the early stages, but later symptoms include raised blood pressure, abnormal swelling and protein in the urine.