Drug-induced labor increases the risk for a very rare -- but often fatal -- delivery complication known as amniotic-fluid embolism, a new study confirms.
Researchers in Canada concluded that labor induction doubles a woman’s risk for developing the complication, which is a leading cause of delivery-related maternal death.
About one in five births in the U.S. involves medical induction, and the researchers believe the practice may be responsible for as many as 40 cases of amniotic-fluid embolism and 15 deaths each year in this country.
Labor induction is often medically necessary, such as when the baby is full-term and continuing the pregnancy presents a risk to either mother or baby.
But labor induction is also increasingly performed when there is no medical reason for it, usually for the convenience of either the physician or the parents-to-be.
Michael S. Kramer, MD, one of the study’s researchers, says anyone considering elective labor induction should be aware of the risk.
“This finding should give people pause when they are contemplating an induction that is not medically indicated,” he tells WebMD. “This complication is very rare, but it is also very serious.”
Risk of Fatal Embolisms
The causes of amniotic-fluid embolism are not well understood.
The condition occurs with little warning during or shortly after delivery, when amniotic fluid enters the mother’s bloodstream, causing life-threatening respiratory distress, a drop in blood pressure, and shock.
In an effort to get a better idea of who is most at risk for the condition, Kramer and colleagues at Montreal’s McGill University and the Canadian Institute of Health Research examined more than 3 million Canadian hospital deliveries performed between 1991 and 2002.
The researchers identified 180 cases of amniotic-fluid embolism, 24 of them fatal. That equaled six cases per 100,000 deliveries, and just under one death per 100,000 deliveries.
The researchers found that overall risk for an embolism was twice as high among women whose labors were medically induced.
The risk of a fatal embolism was 3 1/2 times higher among women who had induced labors than among those who did not.
Other risk factors associated with the delivery complication included having diabetes, increased maternal age, and vacuum- and forceps-assisted deliveries.
While the absolute risk associated with labor induction was low -- no more than five cases and two deaths per 100,000 induced births -- it was not insignificant, critical care specialist Jason Moore, MD, tells WebMD.
“More and more deliveries involve medical induction,” says the University of Pittsburgh Medical Center assistant professor. “This is an important study because it refines our understanding of the risk factors.”
Early diagnosis of amniotic-fluid embolism is difficult. Because it progresses so quickly, diagnosis is often confirmed only after the patient has died.
In an editorial accompanying the Canadian study, Moore wrote that a clearer understanding of the risk factors associated with amniotic-fluid embolism could help clinicians identify at-risk women earlier.
But he tells WebMD there is no guarantee this would lead to fewer deaths.
“We really can’t say that, because the only treatment we have to offer is supportive care,” he says.
By Salynn Boyles, reviewed By Louise Chang, MD
SOURCES: Kramer, M. The Lancet, Oct. 21, 2006; vol 368: pp 1444-1448. Michael S. Kramer, MD, scientific director, Institute of Human Development and Child and Youth Health, Canadian Institute of Health Research; medical faculty, department of pediatrics and department of epidemiology and biostatistics, McGill University, Montreal. Jason Moore, assistant professor of critical care medicine, University of Pittsburgh Medical Center.