Maternal AB Blood Type May Multiply Risk of Preeclampsia


WASHINGTON — Blood type AB appears to be a risk factor for preeclampsia, based on the findings of a population-based study of 100,000 consecutive pregnancies in Finland.

Maternal blood type, routinely recorded in pregnancy, may be another way of identifying women at risk for preterm preeclampsia, especially those with other risk factors such as a high body mass index, first pregnancy, or twin pregnancy, said Dr. Hannele Laivuori of the department of medical genetics at the University of Helsinki and colleagues. The results were presented as a poster at the annual congress of the International Society for the Study of Hypertension in Pregnancy.

To examine whether ABO blood type and factor V Leiden clotting factor are associated with preeclampsia risk, the researchers reviewed data from a national registry of blood types of pregnant women and a national registry of medical records.

The nested study population included 248 women who met criteria for preeclampsia and 679 women without preeclampsia who were control subjects. The women gave blood samples and completed questionnaires to supplement the information from their medical records.

Overall, women with the AB blood type were more than twice as likely to develop preeclampsia (odds ratio, 2.1) and nearly four times as likely to develop preterm preeclampsia (OR, 3.8) as were women with blood types A, B, or O. Preterm preeclampsia was defined as preeclampsia at less than 34 weeks' gestation. When only a first pregnancy was analyzed, the association between blood type AB and preeclampsia was significant only for preterm preeclampsia.

“Factor V Leiden was not a risk factor for preeclampsia in this study population,” the researchers noted.

Age, education level, and place of residence (rural vs. urban) were similar for those with and without preeclampsia. After investigators controlled for confounding factors, a high body mass index before pregnancy, first pregnancy, and twin pregnancy were significantly associated with an increased risk of preeclampsia.

The findings support those of the few previous studies on this topic, including an Italian study that found women with blood type AB were three times as likely to develop preeclampsia as were women with other blood types (J. Hum. Hypertens. 1995;9:623–5).

The study was supported in part by the Red Cross Finland Blood Service.

Dr. Laivuori stated that she had no relevant financial conflicts to disclose.

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