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Premature Birth: Managing Risk Factors

Created: 11/03/2011
Last Updated: 05/27/2014

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Pregnancy is an exciting time for most women, but it can also be a time of uncertainty. Will my baby be OK? What can I do to ensure a safe and healthy pregnancy? You may have heard stories about babies that arrived weeks before their due dates and wondered if there was anything you could do to make sure this didn’t happen to you.

Premature births present a major public health concern in the United States. "Preterm" or "premature" birth refers to any baby that arrives at 37 weeks or earlier, at least three weeks before its due date. The most serious problems with preterm births tend to arise with babies born at 34 weeks or earlier, but even babies born a week or two early can face complications. Today, 12 percent of U.S. births are premature—that is, one in every eight babies. 

Fortunately, the vast majority of babies in the U.S. are not born too early, but it does make sense to keep this risk in mind and to take whatever steps you can to avoid premature delivery. This is important because prematurity is the leading cause of death among newborn babies and also poses some serious long-term health risks. Babies born prematurely may face lifelong challenges including intellectual disabilities, breathing and respiratory problems, asthma, cerebral palsy, and vision and hearing loss.

Premature births also create a substantial economic burden for families and health care systems. Infants born prematurely have much higher survival rates than they used to, but they are still at increased risk for poor health outcomes. Premature infants cost the United States $26.2 billion, or roughly $51,600 per infant, two-thirds of which is spent on medical care.

The primary risk factors for preterm delivery include having had at least one previous preterm delivery, multiple gestation (twins or triplets), low maternal weight, being African American and short cervical length.

Research has shown that cervical length is a significant predictor of preterm birth. The cervix is the lower, narrow part of the uterus where it joins the vagina. Having a shortened cervix too soon reflects the early effacement, or thinning, of the cervix, creating risk for premature delivery. The shorter your cervix is, the higher the risk of premature birth.

Normal cervical length mid-pregnancy is 30 to 40 millimeters. Women with a cervical length below 30 millimeters may require closer observation or testing because of their risk of spontaneous preterm delivery, although many women with a short cervix still deliver at term. Your health care professional can identify a shortened cervix by taking measurements during the second and third trimesters of pregnancy. The exact stage at which doctors conduct cervical measurements may vary, but they typically begin at some point in the second trimester, around 20 to 24 weeks of gestation. Ask your health care professional about measuring your cervix at least twice during your second trimester, because your cervix may become shortened as the pregnancy advances.

For many years, transvaginal ultrasound (TVU) was the standard method for cervical measurement. This involves inserting an ultrasound wand into the vaginal canal to reach the cervix, making it possible to measure its length. TVU requires a trained ultrasound technician and specialized equipment.

An obstetrician has designed a device that can be used by a physician or midwife to measure the cervix during an office visit. A speculum is inserted, followed by the device, which is then used to measure the vaginal cervix length. Studies have shown that this device, called CerviLenz, is accurate and may provide an easier and less expensive way of measuring the cervix.

If your health care professional finds that you have a shortened cervix, you will be observed more closely throughout your pregnancy, and there are several treatment options that may be recommended. Recent research has shown a decrease in premature births with the use of progesterone therapy in some women. Progesterone can be administered in a number of ways, including as a vaginal gel, capsule or suppository, or intramuscularly as a shot. One recent study of a vaginal progesterone gel found that treatment started before 24 weeks for women with a short cervix was associated with a 45 percent reduction in the rate of preterm birth before 33 weeks and with improved outcomes for the babies.

Cervical cerclage is another treatment that has shown significant reductions in preterm births and infant mortality. Cerclage is a surgical procedure that involves placing a stitch through the cervix, essentially sewing it shut to prevent it from opening too early.

If a woman is in preterm labor, steroids may be given to help mature the baby's lungs and reduce the risk of respiratory distress syndrome in premature babies.

If you are pregnant, find out if you are at high risk for premature birth. Talk to your health care professional about getting your cervical length measured at least twice during the second trimester of your pregnancy. Conducting a cervical measurement is relatively simple and may help ensure a healthier start for your baby.