Treatment for Meconium Aspiration Syndrome Questioned

Study finds flushing of contaminated amniotic fluid makes little difference

THURSDAY, Sept. 1, 2005 (HealthDay News) -- Newborns who pass their first feces into their own amniotic fluid face the possibility of developing meconium aspiration syndrome, a potentially deadly complication, and now a new study says the standard treatment for the syndrome is ineffective.

The report appears in the Sept. 1 issue of the New England Journal of Medicine.

Meconium is the first feces of the newborn. It is thick, sticky and greenish-black in color. Aspiration occurs when the newborn inhales a mixture of the meconium and amniotic fluid, either while in the uterus or just after delivery.

Inhaling meconium happens in about 5 percent to 10 percent of births. It usually occurs when the fetus is stressed during labor, especially when the infant is past its due date. The condition is serious -- meconium aspiration is a leading cause of severe illness and death in newborns.

If the infant breathes while still in the uterus or while still covered by this fluid after birth, the mixture of meconium and amniotic fluid can make its way into the lungs, partially or completely blocking the infant's airways.

The standard therapy for meconium aspiration syndrome is flooding the amniotic cavity with saline, called amnioinfusion, to try to wash away the meconium before it can reach the infant's lungs.

Although widely used in women who have thick meconium staining of their amniotic fluid to reduce the risk of meconium aspiration syndrome or death, amnioinfusion doesn't work, researchers report.

"Amnioinfusion has been used for some time as a method to prevent meconium aspiration syndrome," said lead author Dr. William Fraser, director of obstetrics and gynecology at the University of Montreal. "But we found no evidence of a benefit of amnioinfusion, and no reduction in the risk of meconium aspiration syndrome."

In their study, Fraser's team assigned 1,998 pregnant women who were in labor at 36 or more weeks of gestation, and who had thick meconium staining of the amniotic fluid, to amnioinfusion or standard care.

Fraser's group found that moderate/severe meconium aspiration syndrome or infant death occurred in 44 infants of women in the amnioinfusion group, and in 35 infants of women in the standard care group. Five infants in the amnioinfusion group died, as did five in the standard-care group, the researchers note.

Based on these findings, Fraser said he and his colleagues cannot recommend amnioinfusion as a treatment for meconium aspiration syndrome.

Another recent study found that a different method of trying to prevent meconium aspiration syndrome, namely suctioning the infant's airway before the baby takes its first breath, is also ineffective. "It appears that mechanical methods of removing meconium from the upper airway are not effective," Fraser said.

"Medicine has a history of introducing interventions before they have been carefully evaluated," Fraser said. "Amnioinfusion for the prevention of meconium aspiration syndrome was introduced before its effectiveness was tested."

Fraser believes that to prevent meconium aspiration syndrome, one has to prevent the factors that cause the syndrome. "That's trying to prevent perinatal asphyxia," he said.

One expert agrees with the findings of the study.

It is very likely that infants have aspirated meconium before the condition is recognized, and that is part of the reason that amnioinfusion doesn't work, said Dr. Michael Ross, a professor of obstetrics and gynecology and public health at the University of California, Los Angeles School of Medicine.

"If you see a patient in labor with meconium in the amniotic fluid, you shouldn't do amnioinfusion," Ross, who authored an accompanying journal editorial, said. "What you do want to do is to prevent the baby from becoming hypoxic."

Although it's not the standard of care, Ross believes these babies should be delivered early. "One may not want to let a lot of babies go to 42 weeks, which is still the standard of care, because babies spontaneously pass meconium days before delivery. So maybe you want to deliver before that meconium passes," he said. "It's not the standard of care, but it's something worth considering."

More information

The U.S. National Library of Medicine can tell you more about meconium aspiration syndrome.

SOURCES: William Fraser, M.D., director, obstetrics and gynecology, University of Montreal, Quebec; Michael Ross, M.D., M.P.H., professor, obstetrics and gynecology and public health, University of California, Los Angeles School of Medicine; Sept. 1, 2005 New England Journal of Medicine
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