Women who have miscarried or had an abortion run three times the normal risk of having a subsequent low birthweight baby, suggests research in the Journal of Epidemiology and Community Health.

The more miscarriages or abortions a woman has, the greater are her chances of giving birth to a child that is underweight or premature in the future, the research shows.

Low birthweight (under 2500 g) and premature birth (less than 37 weeks) are two of the major contributors to deaths among newborn babies and infants.

The authors used data from the United States Collaborative Perinatal Project, which was set up in 1959 to look at the associations between factors during pregnancy and birth and childhood development.

In total, more than 45,500 mother and child pairs were assessed. Nearly 40% of the mothers had one or two children and almost two thirds were between 20 and 29 years of age.

Rates of low birthweight and premature birth were highest among mothers who were black, young or old, poorly educated, and unmarried.

But there was a strong association between miscarriage and abortion and an early or underweight birth, even after adjusting for other influential factors, such as smoking, high blood pressure and heavy drinking.

Women who had had one, two, or three or more miscarriages or abortions in the past were almost three, five, and 9 times as likely to give birth to an underweight child as those without previous miscarriages or abortions.

Similarly, women who had one miscarriage or abortion were 67% more likely to have a premature birth, while those who had had three or more were over three times as likely to do so compared with those with no history of miscarriage or abortion.

The authors acknowledge that previous research has been inconclusive, with some studies reporting no increased risk while others have found a significantly increased risk.

Nevertheless, women and healthcare professionals should be aware of the potential risks, they conclude.

Source: British Medical Journal