Live birth rates achieved with assisted reproductive technologies can approach the natural fecundity rate in the general population, as long as patient and embryo characteristics are favorable "and there are no barriers to treatment continuation," according to a report in the June 28 issue of the New England Journal of Medicine.
However, when such barriers arise – when women terminate treatment because of financial constraints, stress, lack of treatment success on the first two or three tries, or other reasons – live birth rates associated with ART decline considerably, said Barbara Luke, Sc.D., of the departments of ob.gyn. and reproductive biology, Michigan State University, East Lansing, and her associates.
Discontinuation rates are high even when insurance covers the cost of ART, ranging from 17% to 65% in several studies. "Our results suggest a substantive potential benefit of additional cycles of treatment in many cases, unless physiologically contraindicated," the investigators noted.
To quantify live-birth rates achieved with ART, Dr. Luke and her colleagues analyzed detailed deidentified information in the Society for Assisted Reproductive Technology’s reporting system database, which covers more than 90% of all clinics that provide ART in the United States. They assessed outcomes for 246,740 women who underwent 471,208 treatment cycles over a 5-year period and delivered 140,859 live infants.
Approximately 47% of these women were younger than age 35 years, and 15% were older than age 40.
Overall, live births occurred in 30% of the treatment cycles. A total of 57% of the women had a live birth.
Under optimal conditions, by the third treatment cycle the live birth rate was 65% for transfer of cleavage embryos and 81% for transfer of blastocyst embryos from fresh autologous oocytes.
"The estimated natural fecundity rate of the general population is about 20% per month, and estimated rates of conceiving naturally are 45%, 65%, and 85% after 3, 6, and 12 months, respectively.
"Our optimal estimates – representing the likelihood of a live birth when there are no barriers to treatment continuation – support the hypothesis that similar rates can be achieved by means of ART, in the context of favorable patient characteristics, embryo quality, and treatment method," Dr. Luke and her associates said (N. Engl. J. Med. 2012;366:2483-91).
As an example, the overall cumulative live-birth rate after two treatment cycles was higher than 70% in most women, depending on numerous patient, embryo, and treatment factors.
"Currently, many U.S. states have laws requiring insurance coverage for infertility treatment," but the number of covered cycles "is typically limited to two or three. Our findings show that when autologous oocytes are used, the success rates continue to rise beyond these limits," the researchers noted.
Among the study’s other findings:
• Cycles using donor oocytes were consistently associated with higher rates of live birth than were cycles with autologous oocytes.
• Live-birth rates declined as maternal age increased when autologous oocytes were used, but not when donor oocytes were used. With donor oocytes, live-birth rates were 60%-80% for women of all ages.
• Cycles in which "extra" embryos were cryopreserved – "an imperfect proxy measure of embryo quality" – produced more live births than cycles without cryopreservation.
• Transferring an embryo at the blastocyst stage yielded higher live-birth rates than did transferring at an earlier stage. "This may be an indirect measure of embryo quality or favorable patient characteristics," the investigators said.
• For both autologous and frozen donor oocytes, live-birth rates were highest when two embryos, rather than one or three, were transferred. However, transfer of two embryos also increased the likelihood of multiple gestations.
• For cycles using donor oocytes, the live-birth rate was higher for fresh than for thawed embryos.
This study was supported by the National Cancer Institute, the National Institutes of Health, and the Society for Assisted Reproductive Technologies. Dr. Luke reported no potential financial conflicts of interest, and one of her associates reported ties to Ferring, EMD Serono, MSP Organon, and Theralogix.