Pregnant women are warned by doctors about the possible risk of a preterm labor and birth. Since the cause of most preterm births remain unknown, early “water breaking” during pregnancy can occur in any pregnant woman before 37 weeks of gestation. However, according to a recent study, high levels of naturally-occurring bacteria in the chorion membrane, can make it susceptible to thinning and splitting, leading to a premature birth.

The preterm premature rupture of membranes (PPROM) — composed of two fetal cell layers — the amnion and chorion — accounts for one-third if not all premature births. The amnion layer provides the majority of tensile strength, which is in direct contact with the amniotic fluid while the chorion is metabolically active, and protects the maintenance of pregnancy against infection and regulation of apoptosis, or cell death, says Tulane University. The layers both work to keep maintain a healthy pregnancy throughout gestation. Researchers at Duke University Medical School believe the premature rupturing of the fetal membrane may be a direct cause of the high levels of naturally-occurring bacteria at the site.

Published in the journal PLOS One, study author Amy Murtha and her colleagues, sought to examine the role of bacterial colonization on the fetal membranes and its role in membrane rupture. The membrane samples of 48 women who had just given birth, including those with PPROM, those who had an early birth for other reasons, and those with babies born at full term, were observed. The thickness of the chorion layer as well as bacterial presence at sites both on and far away from the rupture site were compared by the researchers. In addition, the team looked to see if bacteria were present in the membranes and whether bacteria levels correlated with the thinning of the cell layers in the membranes.

The findings revealed the chorion was the thinnest at the rupture site in all of the participants, but the thinning was more commonly found in women who has experienced PPROM. Chorion thinning was not found to be isolated to the rupture site in these patients. “Interestingly, bacteria were present in all fetal membranes, refuting the traditional understanding that fetal membranes are sterile environments. The amount of bacteria present at the rupture site was higher, which the researchers were not surprised to find," according to the news release.

Although they found a probable cause to preterm births, the study authors admit they still know little about the changes occurring within the fetal membrane in the presence of bacteria. However, the findings suggest the thinning of the chorion could be the breeding grounds for these changes to happen. The team of researchers are working to identify the bacteria to determine if specific bacteria is found in PPROM patients. Through identifying this specific bacteria, the researchers may be able to learn about the role of bacterial presence which may lead to preventative treatments.

“For instance, if we think that certain bacteria are associated with premature rupturing of the membranes, we can screen for this bacteria early in pregnancy. We then might be able to treat affected women with antibiotics and reduce their risk for PPROM,” Murtha said. The study highlights possible therapeutic interventions that could target premature births in obstetrics.

The Centers for Disease Control and Prevention reports one of every eight babies is born premature each year in the U.S. The earlier a baby is born, the more severe their health problems they are likely to have, such as cerebral palsy, breathing and respiratory problems, hearing loss, and feeding and digestive problems. More infants die from preterm-related problems than from any other single cause.


Bentley RC, Feng L, Fortner KB, Grotegut CA, Heine PR, Murtha AP et al. Bacteria Localization and Chorion Thinning among Preterm Premature Rupture of Membranes. PLoS One. 2014.