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Prevention of spontaneous preterm birth

INTRODUCTION

Twelve percent of births in the United States occur before 37 weeks and are considered preterm. Approximately 20 percent of preterm deliveries are iatrogenic; they are performed due to medical or obstetrical complications that are believed to put the health of the mother or fetus in jeopardy (eg, intrauterine growth restriction, preeclampsia, placenta previa, nonreassuring antenatal fetal testing). The remaining 80 percent of preterm deliveries are spontaneous, related to preterm labor or preterm premature rupture of the membranes.

Potential interventions for reducing the incidence of spontaneous preterm birth can be classified as primary (aimed at all women), secondary (aimed at eliminating or reducing risk in women with a previous preterm birth), or tertiary (aimed at preterm infants) [1]. While the ability of obstetrical care providers to identify women at risk for preterm birth has improved over the past three decades, application of primary and secondary interventions has not reduced the incidence of preterm delivery, which has actually increased. In the vast majority of cases, it is beyond the capabilities of obstetric medicine to prevent preterm delivery. Neonatal outcome, however, has improved during this interval as a result of widespread use of antenatal glucocorticoids and advances in neonatal care (eg, exogenous surfactant treatment, new methods of mechanical ventilation).

Strategies for the prevention of spontaneous preterm labor and delivery will be reviewed here. Other issues relating to preterm labor and birth are discussed separately (partial list):

IDENTIFICATION OF RISK FACTORS FOR PRETERM BIRTH

In theory, identification of risk factors for preterm delivery before conception or in early pregnancy provides an opportunity for intervention to prevent this complication (table 1). However, many preterm births occur among women with no risk factors and there are few interventions that have been proven to prolong pregnancy in women at risk. (See "Risk factors for preterm labor and delivery".)
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