by: ASRM Office of Public Affairs
Published in ASRM Press Release
For the first time, in Fertility and Sterility, researchers present age-specific probabilities of live birth after IVF with frozen eggs. Although IVF with frozen eggs results in lower live birth rates than fresh IVF cycles, the technique plays an important part in the treatment of infertility patients for whom embryo freezing presents religious or ethical obstacles and for patients whose cycles are interrupted.
Researchers from New York Medical College and the University of California Davis conducted a meta-analysis of oocyte cryopreservation cycles using individualized patient data to report the probability of live-birth from in vitro fertilization (IVF) cycles with intracytoplasmic sperm injection (ICSI) using eggs frozen by each of the two methods.
Analyzing data from infertility patients who used their own eggs, the goal was to find the range of probabilities of live birth as a function of patient age, the freezing method (slow freezing (SF) or vitrification (VF)), number of oocytes thawed, number of oocytes injected, and the number of embryos transferred. These probabilities are presented in detailed tables covering patient ages 25 to 42, for SF and VF cycles, thawing 2, 4, or 6 eggs, injecting 2, 4, or 6 eggs, and transferring 1, 2, or 3 embryos. These factors are interrelated and it should be recognized that live birth probabilities are not solely dependent on the number of embryos transferred, but are affected by the quality of thawed eggs and resulting embryos as shown in the other parameters.
The researchers found that live birth rates declined consistently with increasing patient age regardless of freezing technique, yet live births did occur with eggs frozen as late as age 42 with SF and age 44 with VF.
They began with a literature search for all clinical studies on oocyte cryopreservation done from January 1996 through July 2011. To be eligible for inclusion in the meta-analysis, studies must have reported pregnancy outcomes from cycles using mature, non-donor SF or VF eggs from infertility patients treated with ICSI and IVF. Case studies and studies including mixed cycles (SF and VF eggs in the same transfer, or combinations of fresh or frozen embryos and embryos from frozen oocytes in the same transfer) were excluded from the meta-analysis.
Ten eligible studies yielded data on 2265 cycles undergone by 1805 patients with 11,122 slow frozen eggs and 1,957 vitrified eggs. At the time of egg freezing, the patients were between 20 and 51 years old, with an average age of 34. Cycles using SF eggs resulted in 253 pregnancies and 163 live births; VF cycles resulted in 75 pregnancies and 61 live births.
While survival and fertilization rates were higher for VF eggs than for SF eggs, patient age was not associated with oocyte survival or fertilization success in either method. However, patient age played a significant role in implantation rates. Women whose SF eggs were preserved before age 30 had a greater than 8.9% likelihood of implantation per embryo which declined to 4.3% for embryos from eggs frozen after 40. For vitrification cycles, implantation success declined from 13.2% for embryos from eggs frozen at 30 to 8.6% for embryos from eggs frozen at 40.
ASRM President Linda Giudice, MD, PhD, commented, “These probabilities based on patient age will greatly enhance our ability to counsel women who are considering egg freezing. Although the data used here came from infertility patients with different diagnoses of infertility, the information will also be useful to women who want to preserve their fertility in the prospect of gonadotoxic therapies for cancer and other conditions and, we hope, be useful in gaining insurance coverage for the procedure.”
Cil, AP et al, Age-specific probability of live-birth with oocyte cryopreservation: an individual patient data meta-analysis, Fertility and Sterility, in press.
The American Society for Reproductive Medicine, founded in 1944, is an organization of more than 7,000 physicians, researchers, nurses, technicians and other professionals dedicated to advancing knowledge and expertise in reproductive biology. Affiliated societies include the Society for Assisted Reproductive Technology, the Society for Male Reproduction and Urology, the Society for Reproductive Endocrinology and Infertility, the Society of Reproductive Surgeons and the Society of Reproductive Biologists and Technologists.