摘要：PROBLEM/CONDITION :Since the first U.S. infant conceived with assisted reproductive technology (ART) was born in 1981, both the use of ART and the number of fertility clinics providing ART services have increased steadily in the United States. ART includes fertility treatments in which eggs or embryos are handled in the laboratory (i.e., in vitro fertilization [IVF] and related procedures). Although the majority of infants conceived through ART are singletons, women who undergo ART procedures are more likely than women who conceive naturally to have multiple-birth infants because multiple embryos may be transferred. Multiple births can pose substantial risks for both mothers and infants, including obstetric complications, preterm birth (37 years). This year, single-embryo transfer (SET) rates among all embryo-transfer procedures are presented instead of elective single-embryo transfer procedures previously reported. Nationally, SET rates were 67.3% (range: 38.9% in South Dakota to 90.4% in Delaware), 65.0% (range: 23.6% in Puerto Rico to 89.4% in Delaware), and 60.0% (range: 28.6% in Puerto Rico to 83.1% in Delaware) among women aged 37 years, respectively. In 2017, ART contributed to 1.9% of all infants born in the United States (range: 0.4% in Puerto Rico to 5.0% in Massachusetts). Approximately 73.6% of ART-conceived infants were singleton infants. Overall, ART contributed to 14.7% of all multiple births, including 14.7% of all twin infants and 17.3% of all triplets and higher-order infants. ART-conceived twins accounted for approximately 96.5% (18,890 of 19,570) of all ART-conceived infants born in multiple deliveries. The percentage of multiple births was higher among infants conceived with ART (26.4%) than among all infants born in the total birth population (3.4%). Approximately 25.5% of ART-conceived infants were twins, and 0.9% were triplets and higher-order infants. Nationally, infants conceived with ART contributed to 4.5% of all low birthweight (<2,500 g) infants. Among ART-conceived infants, 20.2% had low birthweight, compared with 8.3% among all infants. ART-conceived infants contributed to 5.3% of all preterm (gestational age <37 weeks) infants. The percentage of preterm births was higher among infants conceived with ART (27.8%) than among all infants born in the total birth population (9.9%). The percentage of low birthweight among singletons was 8.1% among ART-conceived infants and 6.6% among all infants born. The percentage of preterm births among ART-conceived singleton infants was 14.0%, compared with 8.1% among all singleton infants. The percentages of small for gestational age infants was 7.6% among ART-conceived infants, compared with 9.9% among all infants. INTERPRETATION :Although singleton infants accounted for the majority of ART-conceived infants, multiple births from ART still contributed to a substantial proportion of all twins, triplets, and higher-order infants born in the United States. Variations in SET rates among states and territories were noted, reflecting variations in embryo-transfer practices among fertility clinics, which might in part account for higher multiple birth from ART observed in some states and territories. PUBLIC HEALTH ACTION :Reducing the number of embryos transferred and increasing use of SET, when clinically appropriate, can help reduce multiple births and related adverse health consequences for both mothers and infants. Because infants from multiple births are at increased risk for numerous adverse sequelae that cannot be ascertained from the data collected through NASS alone, long-term follow-up for ART infants through integration of existing maternal and infant health surveillance systems and registries with data available from NASS might be useful for monitoring adverse outcomes on a population basis.
