Preventing Premature Birth: Interventions

Frederick R. Jelovsek MD

Preterm births (less than 37 weeks gestation) occur in 11% of all pregnancies. Births before 32 weeks gestation, however, account for most of the newborn deaths and these occur in about 2% of pregnancies. The incidence of preterm birth in the U.S. seems to be slowly rising from about 9.5% to almost 11% in the last 15 years. No one is sure why. Of all preterm births, 50% result from spontaneous preterm labor, 30% from spontaneous rupture of the membranes, which later proceeds into labor and 20% with maternal or baby medical problems in which labor is induced early for the benefit of the baby or mother.

Just because an intervention doesn't prevent preterm delivery doesn't mean it shouldn't be used. Many of the above interventions actually improve outcome by causing increased fetal weight gain or increased lung maturity at a given gestational age even though they don't change the average weeks gestation at delivery.

Calorie supplementation helps if near starvation conditions exist and smoking cessation causes babies to weigh more. Remember at any gestational age, the more a baby weighs the more likely the baby is to survive. Antenatal care doesn't cause less preterm births, but women who have more prenatal visits must take care of themselves in other ways because they will have a lower preterm delivery rate than women who seek less antenatal care.

Many women have stories of how tocolytic medications (terbutaline, ritodrine, magnesium sulfate) prevented them from delivering early, but in fact there are many studies indicating that they don't really prevent labor for more than 48 hours. Similarly, the woman who says "I had to be at bedrest" the entire pregnancy, statistically, probably didn't. That doesn't mean the bedrest didn't help the outcome; the baby probably weighed more when it was born and thus had a better chance at surviving and a lower chance at acquiring some of the prematurity related problems, but the time of delivery was probably what it would have been if mother's activity had been unrestricted.