National Obesity Forum - Children of obese mums ‘more likely to have birth defects'

Obese women are more at risk of having babies with birth defects, say researchers. At least seven types of health problem are more likely to occur if a woman is grossly overweight when she becomes pregnant. The risk of spina bifida is doubled. Other conditions including heart and limb defects and hernia in the diaphragm are between 33 per cent and 63 per cent more prevalent in fat mothers.

Almost one in four women in the UK is obese - defined as having a BMI over 30 - and a further third are overweight. This puts them at higher risk of dying in pregnancy and needing a Caesarean section. Obstetricians are so concerned they have set up a special study group to investigate the problem. Professor Adam Balen, of the Royal College of Obstetricians and Gynaecologists, said: "Being obese has a negative impact on the mother's metabolism and potential health of the early developing foetus. "There are a number of possible contributing factors, but it does seem that obesity is an independent risk factor for some birth defects."

The latest study, reported today in the Archives of Pediatrics and Adolescent Medicine, was carried out by U.S. epidemiologists at the Texas University School of Public Health. They looked at more than 10,000 women who had babies with birth defects and compared them with around 5,000 mothers of healthy children between 1997 and 2002. Seven defects - including spina bifida, heart deformities, missing limbs and protrusion of abdominal organs through the navel - were significantly associated with the mother's obesity.

Professor Kim Waller, who led the study, said: "The study provides another reason for women to maintain a healthy weight." The study excluded women with diabetes - which has already been linked to birth defects - and those with diagnosed gestational diabetes, a condition caused by pregnancy. However, they suspect a similar metabolic mechanism to that occurring in diabetes may be affecting the offspring of obese women. Other explanations could be differences in the type of food eaten by obese women during pregnancy, weight-loss techniques they use or difficulty in scanning them because of their weight, which means birth defects are not diagnosed at an early stage.