Preterm Labor and Premature Birth Research

Health care providers consider labor to be preterm if it starts before 37 weeks of pregnancy. Because a fetus is not fully grown at 37 weeks, and it may not be able to survive outside the womb, health care providers will often take steps to stop labor if it starts before this time. Common methods for trying to stop labor include bed rest and medications that relax the muscles in the uterus involved with labor and delivery.

However, the American College of Obstetricians and Gynecologists (ACOG) recently reported that many of the methods used to stop preterm labor are ineffective. The ACOG announcement confirms NICHD-supported research, which found that home uterine monitors were not effective for predicting or preventing preterm labor.

If efforts to stop labor fail, then the baby could be born prematurely. Premature infants face a number of health challenges, including low birth weight, breathing problems, and underdeveloped organs and organ systems. Many infants that are born prematurely need to stay in the hospital until their health is stable, sometimes several weeks or more.

NICHD Research on Preterm Labor and Premature Birth

Despite attempts to stop labor, many cases of preterm labor end in premature birth. Premature birth occurs in between 8 percent to 10 percent of all pregnancies in the United States; it remains one of the top causes of infant death in this country. Infants who survive being born prematurely are at increased risk for certain life-long health effects, such as cerebral palsy, blindness, lung diseases, learning disabilities, and developmental disabilities.

Current NICHD-supported research is trying to identify markers and predictors of preterm labor and premature birth. In one study, researchers are investigating premature rupture of membranes (PROM), a situation in which the membranes that support the fetus in the womb break (sometimes referred to as "when a woman's water breaks") before the fetus is fully developed. PROM can lead to preterm labor and premature birth. Researchers found that, in some cases, the womb and the fetus produce enzymes, proteins that speed up certain chemical reactions, which can cause the membranes to break apart. Further research is now underway to figure out whether other features may make some women more likely to experience PROM. The findings of this research may lead to new methods of preventing PROM and some premature births.

Past research revealed that certain infections can make a woman more likely to experience preterm labor and give birth early. For instance, women who have bacterial vaginosis, the most common vaginal infection for women of reproductive age, are more likely than other women to experience preterm labor and give birth prematurely. Similarly, women who have trichomoniasis, a sexually transmitted infection, are also more likely to give birth prematurely than women who don't have the infection. It would stand to reason, then, that treating these infections would prevent premature births in these cases. But, NICHD-supported studies have shown that treating these infections is not an effective way to prevent premature birth. Further research is now underway to find other options for treating these infections that may reduce the risk of premature birth. For more information on this research, read the news release on the bacterial vaginosis and the news release on trichomoniasis.

One effective way to understand preterm labor and premature delivery is to study the characteristics of women who have given birth prematurely. One group of NICHD-supported researchers found that, among women who had given birth prematurely in the past, a shortened cervix could be a warning sign in preterm labor for a current pregnancy. With this knowledge, scientists can work to develop ways of preventing this shortening of the cervix, which may help to prevent preterm labor and premature delivery. For more information on this research, read the news release about shortened cervix and premature birth.

In addition, research on preterm labor and premature birth is ongoing through the NICHD's Maternal-Fetal Medicine Units (MFMU) Network, a research program that uses 14 sites around the country to conduct studies related to the mechanisms of pregnancy and birth. Researchers in the MFMU Network recently completed a clinical trial, which showed that the hormone progesterone may prevent repeated premature birth in a specific group of women, those who were carrying a single fetus, and who previously gave birth prematurely, between 20 and 26 weeks of pregnancy. In this trial, the progesterone treatment started between the 16th and 20th week of pregnancy, and continued through the 36th week of pregnancy. This finding may help to reduce future premature births among women who have a history of preterm labor and premature delivery.