Woman's WorldWoman's World
By Jean Talbert, M.D.
Preterm birth-delivery before 37 weeks gestation can be one of the most devastating complications of pregnancy. It is the leading cause of infant mortality in industrialized nations and a major cause of developmental delay such as cerebral palsy, chronic lung disease and visual and hearing impairment in children.
In 2004, half a million babies in the United States were born early. Despite improvements in health care technology, preterm birth rates in Massachusetts have risen more than 40 percent in the past 10 years. Currently, more than 12 percent of births in the United States are premature. Eighty percent of these are as a result of spontaneous preterm labor or rupture of membranes, the rest are deliveries performed early due to maternal or fetal health concerns, such as poor fetal growth.
To reduce the incidence of preterm birth rate, we must have an understanding of why preterm labor occurs and how to prevent or arrest it in its early stages.
The physiologic changes that trigger contractions both term and preterm are not yet fully understood. We suspect that inflammation, intrauterine bleeding and/or overdistension of the uterus may play a part, but the majority of preterm births are unexplained. Women with previous preterm births and multiple gestations (twins, triplets) are at the greatest risk. In fact, approximately 60 percent of multiple births deliver early.
Infertility treatments such as in-vitro fertilization and ovulation induction are major contributors to multiple births in this country. And efforts are under way to reduce this tendency.
A number of behavioral and medical risk factors for preterm birth have been identified. These include cigarette smoking, substance abuse (especially cocaine), less than 18 months between deliveries, low pre-pregnancy weight, poor weight gain, some genital and urinary tract infections, and previous cervical surgery.
Prenatal care affords providers an opportunity to identify risk factors and attempt to modify them. Pregnant women should be counseled regarding the risks of tobacco and drug use during pregnancy. Plus routine nutrition counseling, monitoring of weight gain and testing for genital and urinary tract infections may allow for treatment before complications occur.
A biochemical test for fetal fibronectin in vaginal secretions recently has been introduced as a screen for women at risk for preterm birth. Unfortunately, we do not have any clearly effective interventions to alter the outcome.
Traditionally women with preterm labor or early cervical changes have been placed on bed rest. This is difficult physically and emotionally for most women and often presents a financial burden if the woman was employed outside the home or has other children to care for. Although, bed rest can reduce contractions, increase uterine blood flow and improve fetal growth, it has not been proven to effectively reduce the incidence of preterm birth. Nonetheless, there is as yet, no other proven effective strategy. Recently, some studies have shown some benefit of progesterone therapy in women with prior preterm births. This involves weekly injections or daily vaginal suppositories from 18-37 weeks gestation. This has not been shown to be effective after signs and symptoms of preterm labor appear. Several studies have reported a decreased incidence of preterm birth in high and low risk women taking fish oil or docosahexaenoic acid supplements but the data, so far, are inconclusive. Diets low in saturated fats and rich in fish, low-fat dairy products, whole grains, fruits, vegetables and legumes may also be beneficial but the data have not been confirmed.
Once preterm labor is diagnosed, a number of medications are used to arrest the labor. These medications include terbutaline, magnesium, nifedipine and in some cases, indomethacin. These medications generally are administered in a hospital setting and are effective in prolonging pregnancy for several days. Longer use adds little additional benefit and has some risks to the mother and in some cases the fetus.
Antibiotics are of no benefit unless a specific infection has been identified. Women at significant risk of proceeding to preterm delivery also receive a course of corticosteroids. This effectively reduces the incidence and severity of respiratory distress, brain hemorrhage and bowel complications in the newborn. Fortunately, significant advances have been made in the care of preterm babies in specialized neonatal intensive care units (NICUs). Women who arrive at community hospitals with a threat of preterm delivery often are stabilized and transferred to centers with NICUs.
Prevention of preterm birth remains one of the greatest challenges in obstetrics. The costs to society in terms of the medical care and special needs of children born prematurely are tremendous. Identification and modification of risk factors is helpful, but it appears we will need to have a better understanding of the physiology of preterm labor before we can effectively reduce the escalating rate of preterm birth.
(Dr. Talbert is a board certified OB/GYN specialist practicing with Cape Obstetrics, Midwifery & Gynecology in Falmouth and Sandwich, 508-457-0088.)