Contribution of assisted reproductive technology and ovulation-inducing drugs to triplet and higher-order multiple births--United States, 1980-1997.

In the United States, pregnancies associated with assisted reproductive technology (ART) or ovulation-inducing drugs are more likely to result in multiple births than spontaneously conceived pregnancies (1). In addition, triplet and higher-order multiple births are at greater risk than singleton births to be preterm (< or = 37 completed weeks' gestation), low birthweight (LBW) (i.e., < or = 2500 g), or very low birthweight (i.e., < 1500 g), resulting in higher infant morbidity and mortality (2). Because preterm and LBW infants often require costly neonatal care and long-term developmental follow-up, the continuing increase in triplet and higher-order multiple births causes concern among health-care providers and policymakers (3). This report provides estimates of the contribution of ART and ovulation-inducing drugs to these birth outcomes for 1996 and 1997, and summarizes trends during 1980-1997, which indicate that the ratio of triplet and higher-order multiple births has more than quadrupled and that a large proportion of this increase can be attributed to ART or the use of ovulation-inducing drugs.