When I was pregnant with my first child 17 years ago, I had the usual worries compounded by my knowledge as an obstetrician and high-risk pregnancy specialist. I knew first-hand the impact of prematurity and other complications. Like other moms-to-be, I hoped to deliver a healthy baby. As a research physician, I was eager for evidence-based knowledge to make this a reality.
Because it was my first pregnancy, my doctor couldn't tell me whether my risks were any higher than other expecting moms. Beyond the basic risks known at the time--smoking, drinking, and prior history--the medical field just didn't have the evidence back then.
Over the ensuing years, I have witnessed the advances in our understanding of preterm birth. Now, not only can we identify, measure, and track many of the warning signs, we also have some preventative therapies. Today, I am able to tell my patients about their risks for delivering a baby too early, and I can offer several effective interventions. In recognition of Prematurity Awareness Month, and specifically, World Prematurity Day, November 17, I share some thoughts and observations on what we've learned and what we hope to learn still through ongoing research.
Preterm birth: What is it and who's at risk?
Normally, a pregnancy lasts 40 weeks. A baby born before 37 weeks of gestation is defined as premature. Each year, 1 out of every 10 infants is born prematurely in the United States. Globally, the rates are higher. Around 1 million preterm babies die each year, and too many suffer some type of lifelong physical, neurological, or educational disability, often at great cost to families and society. Complications from preterm birth are the leading global cause of death among children under 5 years of age.
Risk factors for preterm birth include low and high maternal age and low socioeconomic status. Historically, African-American women have been at a high risk for preterm birth. There also are medical risk factors, such as a history of preterm birth, carrying more than one baby, infection, high blood pressure, and problems with the cervix.
Prevention: What research has taught us
Studies have prompted us to change the way we define "full-term" pregnancy, to reduce elective deliveries, and to develop new treatment strategies for preterm birth complications. The last weeks of pregnancy are defined by four categories: "early term," beginning at 37 weeks; "full term," starting at 39 weeks; "late term" at 41 weeks; and "post term" at 42 weeks and beyond. We know that babies born at 39 weeks have fewer respiratory problems and are better able to feed and control their temperature. These findings have strengthened the recommendation to wait until at least 39 weeks before delivering, unless there is a medical reason. We recognize that despite enormous medical advances, sometimes delivering a baby early is the best option for the survival of mom and baby.
We now have markers to evaluate for risk of early delivery, such as monitoring the length of the cervix. A short cervix in the late second trimester, around 20 to 24 weeks, is associated with a high risk of preterm birth. We also can evaluate the secretions of the cervix to detect a much-needed protein that can predict delivery within the next 7 days.
Research has given us many treatment options that weren't available a decade ago. We now have evidence to support progesterone therapy for women at high risk of preterm birth. This includes women with a prior spontaneous preterm birth or a very short cervical length. Another intervention is low-dose aspirin for women at high risk of preeclampsia, a condition associated with preterm birth. Women who are morbidly obese and have high blood pressure and a history of preeclampsia can reduce their risk of developing preeclampsia again by taking low-dose aspirin. Generally, aspirin isn't recommended during pregnancy.
In the coming years, NIH will sharpen its focus on preventing preterm birth. We are launching a study in mothers who are at high risk because of a shortened cervix and are expecting twins. We recently announced $46 million in research grants for the Human Placenta Project, an initiative that aims to monitor the growing placenta in real-time throughout a woman's pregnancy. Many problems of pregnancy--such as preeclampsia, preterm birth, and even stillbirth--can occur because of placental problems. These grants promise to help researchers develop new tools to monitor the placenta from the earliest stages of pregnancy, enabling physicians to identify problems sooner and intervene more quickly.
In addition to understanding prematurity and developing preventative therapies, we also focus on optimizing the outcome for babies born too early. Preterm birth and all it involves is a subject of great interest both nationally and globally. These infants are at high risk for heart disease, diabetes, and, potentially, even cancer as they grow.
In my new role as acting director of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, I am honored to lead efforts to understand all causes of preterm birth: genetic, environmental, behavioral, and social. I also recognize that preventing preterm birth will improve outcomes not just for babies and families, but also for the health of the nation.