Amniotic fluid infections linked to premature births

Times Staff Writer

Microbes in the wrong place at the wrong time -- a woman’s amniotic fluid during pregnancy -- may play a role in causing premature births, according to a study published in the online journal PLoS ONE.

Using sensitive molecular techniques, researchers found a greater quantity and variety of bacteria and fungi in a significant portion of women who gave birth prematurely. The more severe the infection, the earlier the women were likely to give birth.

The amniotic sac, which surrounds a fetus, has long been considered a protected, almost inviolable, site.

“Certain kinds of organisms have been known to get in and not necessarily cause any harm,” said Dr. David Relman, an infectious disease specialist at Stanford University School of Medicine and the study’s senior author. “But in general, bugs don’t belong there.”


One in eight American infants is born before full term, which is defined as 37 completed weeks.

The high rate is attributed in part to assisted reproduction, which often results in twins or triplets. But the cause of about half of all spontaneous premature births is a mystery.

Babies born too early can have learning disabilities, neurological problems, lung diseases and cerebral palsy. Prematurity is the leading cause of infant mortality in the United States, accounting for more than a third of all infant deaths, according to the national Centers for Disease Control and Prevention.

Dr. Dan DiGiulio, a research associate in Relman’s laboratory, used two techniques of molecular biology -- polymerase chain reaction and DNA sequencing -- to look for microbes in amniotic fluid samples from 166 women in preterm labor. Of these women, 113 went on to deliver prematurely and 53 carried their babies to full term.


DiGiulio found evidence of infection in 15% of the samples, all from women who gave birth early. The microbes found represented one fungal and 17 bacterial species, including one that had never been identified, according to the report published Monday.

One of the most common was Leptotrichia, which can be found in the mouth and the vagina. Both gum disease and bacterial vaginosis have been linked with a higher risk of premature delivery.