Finding the causes of prematurity

About half of premature births result from spontaneous preterm labor, the causes of which are unknown. Infections have long been suspected among the putative causes, however many studies attempting to establish this have been unsuccessful. Although no specific bacterium has been linked to preterm labor, studies suggest that the body's natural immune response to infections may play a role. Infections lead to inflammation, which in turn may cause the release of substances that may trigger labor.

A number of March of Dimes grantees are seeking to improve understanding of a possible pathway from infection to preterm labor. For example, PRI grantee Michal Elovitz, MD, of the University of Pennsylvania School of Medicine, is studying substances that are involved in the early stages of the inflammatory process in order to develop a blood test that could identify women at special risk. Emmet Hirsch, MD, a PRI grantee at North Shore University Health System in Evanston, Illinois, is investigating how a family of immune system proteins may regulate the processes by which infection may lead to preterm labor.

Which bacteria or other microorganisms can set off this process remains uncertain. Cultures of the reproductive tract of pregnant women have not revealed any consistent microorganism that could be related to preterm labor. Absence of bacterial growth in cultures has been accepted traditionally as evidence of absence of infection. Recently, however, it has become possible to find microorganisms that may not grow in the traditional culture media. Linda Giudice, MD, PhD, a PRI grantee at the University of California at San Francisco, and David Relman, MD, a PRI grantee at Stanford University are using new genetic technologies to identify microorganisms in the reproductive tract that have eluded traditional cultures. If these efforts identify previously unculturable microorganisms, it will be possible to approach the older question of infection as a cause of preterm labor.

Most common questions

Is premature birth a serious health problem?

Yes. Premature babies are at increased risk of newborn health complications, including breathing and intestinal problems and bleeding in the brain. They also are at increased risk of death and lasting disabilities, including intellectual disabilities, behavioral problems, cerebral palsy and vision and hearing loss.

What is late-preterm birth?

Late-preterm birth refers to babies born between 34 and 36 weeks of pregnancy. More than 70 percent of premature babies are born at this time. While these babies are usually healthier than babies born earlier, they are 3 times more likely to die in the first year of life than full-term infants. They also are at increased risk of newborn health problems, including breathing and feeding problems. Some late-preterm births result from early induction of labor or cesarean delivery due to pregnancy complications. However, in some cases, early delivery may occur without good medical justification. Unless there are medical problems, women should wait until at least 39 weeks to schedule an induced labor or c-section to prevent possible prematurity-related problems in their babies.

Which women are at greatest risk for premature birth?

Three groups of women are at greatest risk. These include women who have had a previous premature birth, women who are pregnant with twins or more, and women with certain abnormalities of the uterus and cervix. Treatment during pregnancy with the hormone progesterone can help reduce the risk of another premature birth in some women who have had a previous premature birth. These women should discuss with their health care provider whether this treatment is right for them.

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