Obese women 'more likely to have children with birth defects'

Obese pregnant women are at significantly greater risk of having children with birth defects, a study has shown.

Scientists found that being seriously overweight at the start of a pregnancy was associated with a wide range of congenital abnormalities.

Compared with women of normal weight, obese mothers were more than twice as likely to give birth to children with spina bifida.

The neural tube defect occurs when nerves of the spinal cord are left exposed and unprotected by the vertebrae.

The general risk of babies being born with neural tube defects, which affect the brain and spinal cord, was almost doubled for obese women.

Obesity was also associated with an increased risk of heart defects, cleft palate, hydrocephaly or “water on the brain”, anal abnormalities, and reduction in limb size.

However, the British researchers pointed out that because these defects are rare to start with, even a significant increase in risk meant the chances of them occurring were still small.

An estimate of absolute risk suggested that 0.47 more births per 1,000 were likely to be affected by neural tube defects if the babies’ mothers were obese during pregnancy.

The same calculation for serious heart defects indicated an incident increase of 0.61 per 1,000 births.

Across Europe, around 2% of babies are born with a birth defect that will affect their ability to survive and function normally. The most common birth defects are those affecting the limbs, such as missing or additional fingers and toes or “clubfoot”.

The new research, reported yesterday in the Journal of the American Medical Association, involved pooling data from 57 previous studies looking at body mass index (BMI) and birth defects.

BMI is a measurement that relates height and weight, with a score of 30 or above defining obesity. People with BMIs of 25 to 29.9 are said to be “overweight”.

Dr Katherine Stothard and colleagues from Newcastle University wrote: “Maternal obesity is associated with an increased risk of a range of structural anomalies, although the absolute increase is likely to be small. Further studies are needed to confirm whether maternal overweight is also implicated.”