Problem/condition: Since the first U.S. infant conceived with Assisted Reproductive Technology (ART) was born in 1981, both the use of advanced technologies to overcome infertility and the number of fertility clinics providing ART services have increased steadily in the United States. ART includes fertility treatments in which both eggs and embryos are handled in the laboratory (i.e., in vitro fertilization [IVF] and related procedures). Women who undergo ART procedures are more likely to deliver multiple-birth infants than those who conceive naturally because more than one embryo might be transferred during a procedure. Multiple births pose substantial risks to both mothers and infants, including pregnancy complications, preterm delivery, and low birthweight infants. This report provides state-specific information on U.S. ART procedures performed in 2011 and compares infant outcomes that occurred in 2011 (resulting from procedures performed in 2010 and 2011) with outcomes for all infants born in the United States in 2011.
Reporting period covered: 2011.
Description of system: In 1996, CDC began collecting data on all ART procedures performed in fertility clinics in the United States as mandated by the Fertility Clinic Success Rate and Certification Act of 1992 (FCSRCA) (Public Law 102-493). Data are collected through the National ART Surveillance System (NASS), a web-based data collecting system developed by CDC.
Results: In 2011, a total of 151,923 ART procedures performed in 451 U.S. fertility clinics were reported to CDC. These procedures resulted in 47,818 live-birth deliveries and 61,610 infants. The largest numbers of ART procedures were performed among residents of six states: California (18,808), New York (excluding New York City) (14,576), Massachusetts (10,106), Illinois (9,886), Texas (9,576), and New Jersey (8,698). These six states also had the highest number of live-birth deliveries as a result of ART procedures and together accounted for 47.2% of all ART procedures performed, 45.3% of all infants born from ART, and 45.1% of all multiple live-birth deliveries, but only 34% of all infants born in the United States. Nationally, the average number of ART procedures performed per 1 million women of reproductive age (15-44 years), which is a proxy indicator of ART use, was 2,401. In 11 states (Connecticut, Delaware, Hawaii, Illinois, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, and Virginia), the District of Columbia, and New York City, this proxy measure was higher than the national rate, and of these, in three states (Massachusetts, New Jersey, and New York) and the District of Columbia, it exceeded twice the national rate. Nationally, among ART cycles with patients using fresh embryos from their own eggs in which at least one embryo was transferred, the average number of embryos transferred increased with increasing age (2.0 among women aged <35 years, 2.3 among women aged 35-40 years, and 2.9 among women aged >40 years). Elective single-embryo transfer (eSET) rates decreased with increasing age (12.2% among women aged <35 years, 4.7% among women aged 35-40 years, and 0.7% among women aged >40 years). Rates of eSET also varied substantially between states (range: 0.7% in Idaho to 53% in Delaware among women aged <35 years). The number of ART births as a percentage of total infants born in the state is considered as another measure of ART use. Overall, ART contributed to 1.5% of U.S. births (range: 0.2% in Puerto Rico to 4.5% in Massachusetts) with the highest rates (≥3.5% of all infants born) observed in four states (Connecticut, Massachusetts, New Jersey, and New York state), and the District of Columbia. Infants conceived with ART comprised 20% of all multiple-birth infants (range: 4.7% in Puerto Rico to 41.3% in New York state), 19% of all twin infants (range: 4.1% in Mississippi to 39.7% in Massachusetts), and 32% of triplet or higher order infants (range: 0 in several states to 71.4% in Hawaii). Among infants conceived with ART, 45.6% were born in multiple-birth deliveries (range: 23.1% in Delaware to 61.3% in Wyoming), compared with only 3.4% of infants among all births in the general population (range: 1.9% in Puerto Rico to 4.8% in New Jersey). Approximately 43% of ART-conceived infants were twins, and 3% were triplets and higher order infants. Nationally, infants conceived with ART comprised 5.7% of all low birthweight (<2,500 grams) infants (range: 0.6% in Puerto Rico to 15% in Massachusetts) and 5.9% of all very low birthweight (<1,500 grams) infants (range: 0.8% in Mississippi to 17.3% in Massachusetts). Overall, among ART-conceived infants, 31% were low birthweight (range: 18% in District of Columbia to 44.6% in Puerto Rico), compared with 8.1% among all infants (range: 6% in Alaska to 12.5% in Puerto Rico); 5.7% of ART infants were very low birthweight (range: 0 in North Dakota to 8.5% in Hawaii), compared with 1.4% among all infants (range: 0.9% in Alaska to 2.2% in Mississippi). Finally, ART-conceived infants comprised 4.6% of all infants born preterm (<37 weeks; range: 0.5% in Puerto Rico to 13% in Massachusetts) and 5.2% of all infants born very preterm (<32 weeks; range: 0 in Wyoming to 17.1% in Massachusetts). Overall, among infants conceived with ART, 36.2% were born preterm (range: 12.5% in Vermont to 56.9% in Puerto Rico), compared with 11.8% among all infants born in the general population (range: 8.8% in Vermont to 17.6% in Puerto Rico); 6.7% of ART infants were born very preterm (range: 0 in Wyoming to 12.5% in Alaska), compared with 1.9% among all infants born in the general population (range: 1.3% in Wyoming to 3.0% in Puerto Rico). The percentage of infants conceived with ART who were low birthweight varied from 8.8% (range: 3.9% in the District of Columbia to 17.9% in Puerto Rico) among singletons, to 56.4% (range: 34.6% in Vermont to 70.4% in Mississippi) among twins, and 95.7% (range: 79.5% in North Carolina to 100% in several states) among triplets or higher-order multiples; comparable percentages for all infants were 6.4% (range: 4.5% in Idaho and Oregon to 11.3% in Puerto Rico), 56.3% (range: 47.7% in Vermont to 72.1% in Puerto Rico), and 93.9% (range: 50% in Wyoming to 100% in several states), respectively. The percentage of ART infants who were preterm varied from 13.2% (range: 7.3% in the District of Columbia to 28.6% in Puerto Rico) among singletons, to 61.8% (range: 46% in the District of Columbia to 82.7% in Oklahoma) among twins, and 97.1% (range: 76.9% in Iowa to 100% in several states) among triplets or higher-order multiples; comparable percentages for all infants were 10.1% (range:7.5% in Oregon to 16.6% in Puerto Rico), 57.3% (range: 46.8% in New Hampshire to 68.8% in Louisiana), and 93.4% (range: 73.3% in Rhode Island to 100% in several states), respectively. Only nonsuppressed values from reporting areas are provided to protect confidentiality.
Interpretation: The percentage of infants conceived with ART varied considerably by state (range: 0.2% to 4.5%). In most states, multiples from ART comprised a substantial proportion of all twin, triplet, and higher-order infants born in the state, and the rates of low birthweight and preterm infants were disproportionately higher among ART infants than in the birth population overall. Even among women aged <35 years, for whom elective single embryo transfers should be considered (particularly in patients with a favorable prognosis), on average, two embryos were transferred per cycle in ART procedures, influencing the overall multiple infant rates in the United States. Compared with ART singletons, ART twins were approximately 5 times more likely to be born preterm, and approximately six times more likely to be low birthweight. Singleton infants conceived with ART had slightly higher rates of preterm delivery and low birthweight than among all singleton infants born in the United States. However, all multiple-birth infants, regardless of whether they were ART-conceived or not, were more likely to be preterm and low birthweight compared with singletons. Further, ART use per population unit was distributed disproportionately in the United States, with 11 states showing ART use above the national rate. Of the four states (Illinois, Massachusetts, New Jersey, and Rhode Island) with comprehensive statewide-mandated health insurance coverage for ART procedures (e.g., coverage for at least four cycles of in vitro fertilization, three states (Illinois, Massachusetts, and New Jersey) also had rates of ART use >1.5 times the national level. This type of mandated insurance has been associated with greater use of ART and might account for the differences in per capita ART use observed among states.
Public health actions: Reducing the number of embryos transferred per ART procedure and promoting eSET procedures, when clinically appropriate, are needed to reduce multiple births and related adverse consequences of ART. Improved patient education and counseling on the health risks of having twins might be useful in reducing twin births given that twins account for the majority of ART-conceived multiple births. Although ART contributes to increasing rates of multiple births, it does not explain all of the increases, and therefore other explanations for multiple births not investigated in this report, such as the possible role of non-ART fertility treatments, warrants further study.