Preventing Premature Births

By Christine Haran

Few sights are as heart wrenching as that of a tiny premature baby hooked up to a web of plastic medical tubing. Although more and more of these babies will survive, many will have physical and developmental disabilities.

The only way to prevent these lifelong problems is to prevent premature birth. But premature delivery is on the rise in the United States. According to the March of Dimes, the rate of premature birth increased 21 percent between 1981 and 2001. While some risk factors for premature delivery are beyond our control, prenatal care and lifestyles changes can help women lower their risk of having a premature delivery.

Attention to the early warning signs of premature labor may also help delay premature births. In fact, the American College of Gynecologists has released new guidelines on the use of the hormone progesterone to prevent premature labor in certain women. Below, Nancy Green, MD, medical director of the March of Dimes and an associate professor of pediatrics at the Albert Einstein College of Medicine in New York City, discusses causes of premature birth and how women can help increase the likelihood that their pregnancies will be full-term.and their babies will be healthy.

How does the body know when to go into labor?

Normal labor and delivery are presumably triggered by a complex set of physical and chemical processes. Hormonal levels, which help to maintain pregnancy, are known to change dramatically as labor approaches. Other potential triggers for delivery include signals from the uterus due to stretching as the baby grows. These processes may be the same or may be different for preterm delivery.

What is the normal length of gestation?

The average length is 40 weeks, and normal is considered 38 to 42 weeks. The birth is considered preterm if it is less than 37 completed weeks of gestation.

How big a problem is preterm delivery in the US?

Preterm delivery is an enormous problem in the United States. As of 2002, 12 percent of all deliveries were preterm. That makes the United States about 27th or 28th of industrialized nations in terms of adequate birth weights and gestational lengths. So we're pretty far down there -- around Cuba -- and the problem is getting worse annually over the last 20 years, not better.

What are the causes of preterm delivery?

About half of all the spontaneous deliveries happen for unknown reasons. So when you ask about, "What are the causes?" I can only address that half that we know about. Most preterm deliveries are due to spontaneous preterm labor, but about 10 percent of the total are due to spontaneous rupturing of the membranes, meaning the sac in the uterus that holds the fetus breaks too soon.

About 20 percent or 25 percent of premature deliveries are so-called "medically indicated." For example, inducing preterm labor and delivery is the best treatment for preeclampsia, which is a condition that characterized by high blood pressure, weight gain and swelling. With improved technology, with maternal monitoring and fetal monitoring, those pregnancies are intentionally delivered early for the sake of the health of the mother and baby.

What increases the risk for a preterm birth?

If you've already had a preterm birth you are at about 30 percent increased risk of having another one. If you've had a history of two previous preterm births, then your risk of having a third preterm birth is up to 70 percent.

Twins have about a 50 percent chance of being born premature, and for triplets, it's about an 83 percent chance of being born premature. The rate of twins in the US population has been increasing steadily, in part, due to the increase in the average age of mothers, as well as the use of hormones and other forms of reproductive technologies. The 2001 data, which is the most current for the United States, find that 3.2 percent of all US births are multiples. As the rate of multiples has increased that has, in part, contributed to the rise in preterm births.

Other risk factors are infections in the mom and certain structural defects in the uterus and the cervix. Then there are a bunch of risk factors that are associated with preterm birth but don't necessarily cause preterm birth. Those include women who smoke during pregnancy, women who are at the extremes of weight (either underweight or very overweight), African-American women (for reasons which I wish we knew but don't), women of low socioeconomic status, and women with certain unhealthy lifestyles that involves alcohol abuse and illicit drug use.

Are underlying health problems associated with preterm delivery?

Certainly any underlying health problem can increase risk; hypertension and diabetes are the most common conditions associated with preterm birth, but then other things like autoimmune disorders are associated with an increased risk of preterm birth. Then there are less common problems, like women who have specific bleeding disorders.

Is there anything women can do to reduce risk for preterm birth?

There's a lot that a woman can do to reduce her risk of having a premature baby, even though that doesn't guarantee she won't have one. Certainly before pregnancy is the best time to detect and treat any kind of underlying health problem, such as diabetes, weight problems, smoking or hypertension. So "preconception" health and health care is very important. Once a woman is pregnant, she can maintain a healthy lifestyle, have good prenatal care, be screened for underlying medical conditions.

What are the signs and symptoms of preterm labor?

The signs and symptoms of preterm labor are largely the same as those of normal labor, including contractions, changes in vaginal discharge or vaginal bleeding, and lower back pain. Sometimes it's subtle, so it's hard to recognize, or it's just so unexpected, it's not necessarily connected with any risk of preterm delivery. But even when they have those signs and symptoms, they may not recognize them or seek medical help.

What should a woman do if she's having these symptoms?

She should contact her obstetrical provider immediately, and if she can't get in touch with that person, she should go to a hospital or emergency service to be checked. Sometimes it's false labor, and she can be examined and reassured and sent home. But if it's real, then there are things that can be done to improve the outcome of her and the baby. For example, if she has an infection, the doctor can treat the infection with antibiotics.

What are some strategies to avert premature delivery?

Usually the woman would be given tocolytics drugs to help delay delivery for anywhere from one to seven days, usually. And then that would give her time to be treated with antibiotics or whatever, for other kinds of problems such as an infection. If the baby is very preterm, the mother may be given an injection of steroids which can help increase the maturation of the baby's lungs because the lung maturation takes a couple of days with the treatment.

Why is progesterone sometimes used to prevent preterm birth?

Progesterone is one of the hormones that helps maintain a pregnancy, and it's known that levels go down before delivery. That's why progesterone has been tried to prevent prematurity. But we don't really know if that's how progesterone is working. It may have to do with reducing the stretch effects on the uterus and/or the softening of the cervix that contribute to the onset of labor.

In a recently conducted multi-center trial of progesterone, women who had had a previously preterm birth were given weekly injections of progesterone. The women who received the progesterone had about a 30 percent decrease in their rate of premature delivery, and that translates into a big impact in terms of the length of gestation and the effect on the health of the babies who are born.

In response to that study and another one that's related, the American College of Gynecologists came out with clinical guidelines in November. They state that for those women who have had a previous preterm delivery, it appears that progesterone treatment may be effective for decreasing their risk of having another preterm delivery. Who would respond to the progesterone and who wouldn't and the way to deliver the progesterone still needs to be investigated.

What would you say is the biggest misconception about preterm birth?

We've done national surveys of the general public for their perceptions of prematurity, published in the American Journal of Preventive Medicine in the January-February 2003 issue. The two major misperceptions are that prematurity is not a serious problem and that it's the woman's fault if she delivers prematurely. There are ways that women can reduce their risks, but they can't eliminate them.

What kinds of problems do premature babies face?

Depending upon how premature and how small they are, they're at greater risk of a number of serious, immediate and in some cases long-term effects of being premature. Most of these effects are seen in the very premature baby (less than 32 weeks), and those include death and immediate neurologic problems, and then that translates into risks of cerebral palsy, mental retardation, learning and behavior problems. It's been estimated that about half of all long-term serious neurologic problems in childhood are related to prematurity and low-birth weight. So that's huge, and if you think about hospitalization costs and costs to the family and special schools and equipment and difficulties, that translates into an enormous impact on society.

Very premature babies are also at risk for lung problems, trouble with feeding and growth, and trouble fighting off infections. Some of them have risks of permanent problems with vision and hearing.

The babies between 32 and 37 weeks have fewer risks, but they still have increased risks of some of these immediate and long-term ill effects compared to full-term babies.

Christine Haran is a staff medical writer/editor. Haran has been a health journalist for more than seven years, and her work has appeared in Woman's Day, MAMM Magazine, Bride's Magazine, Publishers Weekly and other publications. In 2003, she received an Excellence in Women's Health Research Journalism Award from the Society for Women's Health Research. Haran has a master's degree in journalism from New York University and a bachelor's degree in english from Skidmore College.

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