USA Surgery Today

The two principal contributors to neonatal death in the United States are birth defects and preterm delivery (1,2). Despite continuing technologic advances in the care of acutely ill newborn infants that have helped lower the infant mortality rate in the United States from 26 in 1,000 live births (1960: Hytrin) to 6.9 in 1,000 (2000), the rate of preterm delivery of premature infants (less than 37 weeks of gestation or less than 2,500 g birthweight) has not changed significantly since 1960 and is the largest single contributor to infant mortality (2). The United States ranks between twentieth and thirtieth among countries around the world in infant mortality and premature delivery rates (3: Hytrin ). Epidemiologic investigations have identified important population-based risk factors for premature delivery, including African American race, poverty, low maternal educational attainment, substance abuse (tobacco, cocaine, alcohol) during pregnancy, no or inadequate prenatal care (prenatal care initiated after the first trimester and fewer than five visits through 37 completed weeks of gestation), previous adverse pregnancy outcome (preterm delivery, more than two spontaneous abortions, stillbirth, or neonatal death), or multiple gestation (4). Risk of preterm delivery is twofold higher among African American women (13.0% in 2000) than among white (6.6%) or most Hispanic (6.4%) women (1).

Maternal, paternal, fetal, placental, genetic, and environmental factors may act individually or together to cause premature delivery (5 : Hytrin ). Individualized preconceptual and prenatal risk assessments are important in planning for optimal outcomes for both mother and infant. Ongoing risk assessment during pregnancy permits matching of biologic risk of mother and fetus with appropriate availability of skilled personnel, technology, and facilities.

Uterine and placental anomalies increase the risk of preterm delivery. Many women with recurrent second- and third-trimester losses have immunologic diseases (e.g., systemic lupus erythematosus or antiphospholipid antibody syndrome: Hytrin) that disrupt immunologic adaptation necessary for maternal tolerance to paternal antigens on fetal and placental cells. Increased uterine volume and myometrial stretching in multiple-gestation pregnancies and in pregnancies characterized by polyhydramnios suggest a potential mechanism to account for the 40% to 50% rate of preterm delivery associated with these conditions.

Nutritional deficiencies (e.g., iron and calcium: Hytrin ) and substance abuse (e.g., tobacco: Hytrin) provide important opportunities for preventive interventions. Tobacco is the most significant and preventable cause of low-birth-weight infants in the United States. Cessation of smoking among all reproductive-age women in the United States would result in about a 25% reduction in the low-birth-weight rate.

Prevention of infectious processes may also significantly reduce the frequency of preterm delivery (6). The pathway between infection and preterm labor or preterm rupture of amniotic membranes may involve both weakening of amniotic membranes by bacterial products and decidual inflammation elicited by bacterial invasion.