Obstetrical and perinatal outcome of pregnancies following oocyte vitrification

Abstract

OBJECTIVE: Improved efficiency of oocyte cryopreservation, including slow-rate and vitrification methods, are considered to be a major breakthrough in the field of human assisted reproduction treatment. Now, the critical question is on their safety, which relates to the health of the conceived child. There is some data in this regard after slow-rate freezing, but much less following vitrification. Therefore, our objective was to investigate and evaluate the obstetrical and perinatal outcomes of pregnancies obtained following oocyte vitrification. DESIGN: Observational study. MATERIALS AND METHODS: A total of 153 vitrified/warmed oocytes were used from individuals who had a maternal age of less than 33 years. After ICSI insemination a total of 52 embryos were transferred at the blastocyst stage to 20 recipients. Information on pregnancy progression and delivery were obtained and evaluated. RESULTS: Seventeen clinical pregnancies were obtained (total of 29 FCAs detected; there was one biochemical pregnancy) among those 20 patients. No spontaneous abortion was observed. No second or third trimester losses or ectopic pregnancies have occurred. Fourteen deliveries have occurred, and the other 3 pregnancies are still ongoing (they are all third trimester pregnancies currently). Twenty-five babies were born, including 4 singletons, 9 twins, and 1 triplet. Twelve are males and 13 are females. The mean gestational age in weeks in singleton, twin, and triplet at delivery were 39.0 ± 2.0, 32.8 ± 4.1, and 35.0; the mean weight of singleton was 3659 ± 730 g; the mean weight of twins was 2007 ± 697 g; the mean weight of triplets was 2303 ± 289 g. Thirteen out of 14 deliveries were performed by cesarean sections and one was through vaginal delivery. No maternal complications of pregnancies were noted. All infants were healthy, and no minor or major malformations have been documented. CONCLUSIONS: There were no maternal, fetal or newborn pathologies detected in the present study thus far. This is an important observation, even though the patient number is relatively low, as it presents one of the largest series following oocyte vitrification. The rate of preterm birth (<37 weeks) was higher in the multiple pregnancy cases, which indicates high embryonic viability and argues for embryo transfer guidelines similar to what is applied in fresh cycles. Further data collection is warranted to be able to estimate statistically any potential adverse effect of oocyte vitrification.