TUESDAY, Nov. 27 (HealthDay News) -- Single-child mothers who develop preeclampsia during their pregnancy are more likely to die from heart disease later in life than mothers with multiple children who developed the blood pressure condition during their first pregnancy, a large, new study suggests.

The study was published online Nov. 27 in the journal BMJ.

This is the first time that this increased risk among single-child mothers has been reported and suggests that these women require special monitoring, according to a journal news release.

Preeclampsia is a serious condition in which high blood pressure and protein in the mother's urine develop in the second half of pregnancy.

Researchers looked at data from more than 836,000 Norwegian women who gave birth to their first child between 1967 and 2009. By 2009, nearly 3,900 of the women had died from heart disease.

Overall, women with preeclampsia in their first pregnancy had a higher risk of heart-disease-related death than women who did not have preeclampsia. But the risk was up to nine times higher among women who had one child, compared with 2.4 times higher among those who had more children.

The vast majority of women with preeclampsia can expect a normal lifespan, according to Rolv Skjaerven, a professor at the University of Bergen in Norway, and colleagues.

Although current guidelines say all women with preeclampsia are candidates for special monitoring, these findings suggest that further consideration should be given to single-child mothers, the researchers said.

Women may only have a single child because of underlying health problems such as diabetes -- that discourage or prevent further pregnancies rather than due to preeclampsia itself, the authors concluded.

Although the study found an association among preeclampsia, having one child and maternal death from heart disease, it did not prove a cause-and-effect relationship.

More information

The March of Dimes has more about preeclampsia.