Dec. 21 (HealthDay News) -- Women who've had a miscarriage or an abortion are much more likely than women who haven't to experience a low-birthweight or premature baby in the future, new research shows.

A team at Virginia Commonwealth University looked at data on more than 45,500 mother-and-child pairs enrolled in the United States Collaborative Perinatal Project.

About 40 percent of the mothers had one or two children, and almost two-thirds of the mothers were between ages 20-29. The researchers found that rates of low-birthweight (under 2,500 grams or 5.5 pounds) and premature babies (less than 37 weeks gestation) were highest among women who were black, young or old, poorly educated, and unmarried.

The study also found that women who'd had one, two, or three or more miscarriages or abortions in the past were almost three, five and nine times, respectively, more likely than normal to have an underweight baby.

Women who'd had one miscarriage or abortion were 67 percent more likely to have a premature baby, while women who'd had three or more miscarriages or abortions were more than three times as likely to have a premature baby, compared to women who hadn't had a miscarriage or an abortion.

The study is published in the Journal of Epidemiology and Community Health.

The researchers noted that previous studies have been inconclusive, with some reporting no increased risk and others identifying a significantly increased risk of low-birthweight or premature babies among women who've had a miscarriage or abortion. Despite the conflicting evidence, women and doctors need to be aware of the potential risks, the authors concluded.

SOURCE: BMJ Specialist Journals, news release, Dec. 18, 2007