Today nearly 13 percent of the more than 4 million babies born in the United States each year arrive prematurely—which means moms deliver them earlier than 37 weeks into their pregnancies. That's up from 10.6 percent in 1990. That may not sound like such a big deal, but the younger babies are at birth, the greater their risk of medical conditions such as cerebral palsy and mental retardation. In the long term, premature birth can also affect education level attained and even income earned as an adult. The increase in premature births is due, in part, to the boom in infertility treatments, which can increase the number of multiple births. Improved technology that keeps more premature babies alive is also a factor. "If more babies survive, you have more complications," says neonatologist Maureen Hack, professor of pediatrics at Case Western Reserve University and at Rainbow Babies and Children's Hospital. A study published this week in the New England Journal of Medicine found dramatically higher rates of cerebral palsy (9.1 vs. 0.1 percent) among babies born at 23 to 27 weeks compared to babies born at 37 weeks or later. According to the study, which looked at the health records of 903,402 Norwegian babies born between 1967 and 1983, the preemies received disability pensions at more than six times the rate of the 37 week babies. Karen Springen spoke with Dr. Cathy Spong, chief of the pregnancy aand perinatology branch of the National Institute of Child Health and Human Development. Excerpts:
NEWSWEEK: What can we do to prevent preterm births?
Cathy Spong: Part of the issue is despite everything that we have done and know, preterm births are increasing. It keeps going up a little bit. What's pushing that rise? What can we do to prevent that? Some of it is due to artificial reproduction technology. Babies who are born after assisted reproductive technology (ART) are at increased risk of being born preterm even if they're singletons, but especially if they're multiples.
Do we know why?
We don't know why. Is it due to whatever caused them to be infertile to require ART or is it to the ART itself? That's just one segment of it. Another segment is there's an increase in late preterm births, births between 34 and 37 weeks. That's where the majority of the increase is occurring. Is that due to more medical problems or more at-risk moms? Is it because moms are older? Is it because some might be trying to deliver a little bit earlier because they want to avoid risk? We don't know that answer.
Who's having premature babies?
Your highest risk group is women who have had a prior preterm birth. Those are the women we've targeted for intervention. We have shown that if you give them progesterone, starting at about 16 weeks, you'll reduce their rate of having a subsequent preterm birth by about a third.
But progesterone isn't a cure-all. Last year a study in The New England Journal of Medicine showed that it did not prevent preterm birth in twin pregnancies, right?
Exactly. It's not beneficial for women with multiples. We are currently studying women with a short cervix [another risk factor for premature birth], randomized to progesterone or no progesterone.
Why would a shortened cervix cause women to deliver early?
The cervix is the mouth of the uterus. Normally it's about 4 centimeters long. Perhaps at 20 weeks of pregnancy or halfway through, some people's cervix is only half a millimeter. Once the cervix shortens and dilates, you then deliver. The cervix will thin.
Does a woman know she has this?
No, she doesn't.
What can women actually do to help prevent premature births?
Especially for a woman who's never had a pregnancy before, it's really hard to know. We're planning to do a study on the woman who's never had a baby before. We have right now a solicitation, a request for applications for people to participate in this study. It will hopefully start in the end of 2009.
What about smoking and other things that women can control?
We know cigarette smoking makes your baby small and can make you deliver preterm. If I see a woman right now, what do I say to her? It's important to get good prenatal care and be healthy. If you have any medical condition, get that under control. If you have high blood pressure, get on a medication that's safe for pregnancy before you get pregnant. Start your prenatal vitamins early. Even if you're not ready to get pregnant, start taking a complex vitamin. There was an interesting abstract presented looking at preconceptual folate. Women who supplemented their diet with folate before they became pregnant had lower rates of preterm birth, so I would encourage women to take their folate. Eat a well-balanced diet. Be healthy going into pregnancy. Once you're pregnant, get good prenatal care. Know what your dates are so you know your due date so the baby can be followed better, to know if the baby is growing normally.
What bad habits, other than smoking, increase the risk of premature delivery?
Certain drugs such as cocaine cause the placenta to separate from the wall of the uterus. You could deliver early. Alcohol is strongly associated with fetal alcohol syndrome and fetal alcohol spectrum disorder, which affects the baby's ability to learn. I strongly recommend to my patients to abstain from alcohol from the moment they decide they want to become pregnant.
Does age make a difference?
Women who are at the extremes of age do have higher risks of premature birth. We don't know why. It may be that their uterus isn't conducive to having the placenta develop as well. We don't really know why. It simply may be that for the very young, it hasn't developed to the point that it's ready to carry a baby. Teen moms and older moms are more at risk of pre-eclampsia, which is thought to be due to the placenta not growing into the wall of the uterus as well as it could. Pre-eclampsia is one of the indicated causes of premature birth. It's also known as toxemia. It's when the woman will develop high blood pressure, their kidneys will get affected and spill protein into her urine. She can get other side effects. Her liver can get affected. In the worst-case scenario, she can have seizures. Your highest risk is going to be with your first baby and again, if you have other complications such as high blood pressure or diabetes.
What about obesity?
That's an interesting question. The studies are a little bit conflicting. The majority of the studies would suggest obesity may be a bit protective against preterm birth. But there are so many other problems associated with obesity with pregnancy. It's difficult to monitor, there are much higher risks of heart and congenital abnormalities like spina bifada. Obesity itself is a much greater risk than your potential risk of preterm birth.
What about multiple births?
You want to minimize multiples. Work with the infertility doctor to try to reduce the chances of having multiples.
What else do you wish women knew about premature births?
It's a public-health problem. It affects the baby in the short term and in the long term. Babies who are born preterm don't have optimal fetal development. If we could do more to understand this, we'd improve the health of the nation. If women have the chance to participate in a study to try to understand it, they should do it. Check out the NICHD Web site or talk to their doctor.