Section 3: ART Cycles Using Frozen Nondonor Embryos
How do percentages of embryos transferred that result in implantation for frozen nondonor embryos differ among women of different ages?
As shown in Figure 25 among women using fresh nondonor eggs or embryos, the percentage of embryos transferred that resulted in implantation decreased as the age of the woman increased. Figure 35 shows the same relationship between implantation percentage and the age of the woman when frozen nondonor embryos were transferred; the percentage of frozen nondonor embryos transferred that resulted in implantation decreased as the age of the woman increased (from about 31% among women younger than age 35 to 12% among women older than age 44). In 2011, the percentage of embryos transferred that resulted in implantation among women using frozen nondonor embryos was higher compared with the implantation percentage among women using fresh nondonor embryos in all age groups except among women younger than age 35.
What is the percentage of transfers that result in pregnancies, live births, and singleton live births for ART cycles using frozen nondonor embryos?
Frozen nondonor embryos were used in approximately 21% of all ART cycles performed in 2011 (32,180 cycles). Figure 36 shows different measures of success for ART cycles using frozen nondonor embryos compared with ART cycles using fresh nondonor embryos. In 2011, percentages of transfers that resulted in pregnancies, live births, and singleton live births for ART cycles using frozen nondonor embryos were similar to those for fresh nondonor embryos.
The average number of embryos transferred was lower for cycles using frozen nondonor embryos than for those using fresh nondonor embryos in all age groups. (See the National Summary table for information on the average number of embryos transferred by age group and cycle type.) Cycles using frozen nondonor embryos are both less expensive and less invasive than those using fresh nondonor embryos because the woman does not have to go through the fertility drug stimulation and egg retrieval steps again.
What is the risk of having a multiple-fetus pregnancy or multiple-infant live birth from an ART cycle using frozen?
Multiple-infant births are associated with greater problems for both mothers and infants, including higher rates of caesarean section, prematurity, low birth weight, and infant disability or death.
Part A of Figure 37 shows that among 13,325 pregnancies that resulted from ART cycles using frozen nondonor embryos, approximately 68% were singleton pregnancies, 21% were twins, and 2% were triplets or more. Approximately 10% of pregnancies ended before the number of fetuses could be accurately determined. Therefore, the percentage of pregnancies with more than one fetus might have been higher than what was reported (approximately 23%).
Part B of Figure 37 shows 10,314 live births in 2011 resulted from ART cycles that used frozen nondonor embryos. Approximately 23% of these live births produced more than one infant. This compares with a multiple-infant birth rate of slightly more than 3% in the general U.S. population.
Although total percentages for multiples were similar for pregnancies and live births, there were more triplet or higher order pregnancies than births. Triplet or higher order pregnancies may be reduced to twins or singletons by the time of birth. This can happen naturally (e.g., fetal death), or a woman and her doctor may decide to reduce the number of fetuses using a procedure called multifetal pregnancy reduction. CDC does not collect information on multifetal pregnancy reductions.