Mom's blood reveals baby's hemorrhage risk.

Mom's blood reveals baby's hemorrhage risk

Clinicians have developed an improved means for evaluating a pregnant woman's risk of delivering a baby with a potentially fatal bleeding disorder. Reliably determining which pregnant women face a low risk of carrying such babies could also prevent thousands of unnecessary caesarean sections annually.

An estimated 7.6 percent of all pregnant women have reduced numbers of blood platelets, cell fragments that facilitate clotting. Most of these women have developed a benign pregnancy-related disorder of unknown origin. But some suffer from a serious autoimmune disease, immune thrombocytopenic purpura (ITP). The antibodies of its victims mistakenly destroy blood platelets. The antibodies can also wipe out many of these important clotting agents from a developing child.

Infants born with a severe deficiency of platelets can develop massive brain hemorrhages during the first few weeks after birth. This is especially true of infants delivered naturally, since the birth canal compresses a baby's head. To limit an infant's risk of potentially fatal bleeding, some obstetricians have advised all patients with low platelet counts to schedule caesarean deliveries.

But previous research hinted that infants of women with the benign low-platelet disorder run no such risk. Philip Samuels and his co-workers at the University of Pennsylvania School of Medicine in Philadelphia and colleagues now confirm that observation. They also report identifying a means for detecting those pregnant women who pose a hemorrhage threat to their newborns.

Between 1979 and 1989, the researchers studied 162 pregnant women with lower-than-average platelet counts -- less than 150,000 platelets per cubic millimeter of blood. Though 88 women had been diagnosed with ITP prior to pregnancy, the rest hand no history of abnormal bleeding or signs of ITP. Among the 88 women with obvious ITP, 18 delivered babies with dangerously low blood-platelet levels. By contrast, children born to the 74 women who appeared only to have the benign pregnancy-related platelet abnormality faced no risk of severe hemorrhage, the team reports in the July 26 NEW ENGLAND JOURNAL OF MEDICINE.

"Unless the mother has a known history of ITP, one doesn't need to worry about the fetus and one doesn't need to perform a caesarean section," Richard H. Aster, a hematologist at the Medical College of Wisconsin in Milwaukee told SCIENCE NEWS. Aster wrote an editorial accompanying the research report.

Furthermore, the researchers found that among pregnant women with a history of abnormal bleeding, testing for the ITP antibodies could help determine whether they also pose a hemorrhage risk to their child at birth. Women with ITP whose blood carried on detectable levels of the platelet-destroying antibodies delivered children with sufficient platelet levels to prevent massive bleeding, they report. However, the researchers say the test's predictive power needs confirmation before physicians can rely on it to assess the safety of natural deliveries among these women.