Perinatal outcome of children born after vitrification of blastocysts (5434 Cycles: 11 years experiences)

OBJECTIVE: Vitrification has been recognized as a useful method for cryopreservation of human blastocysts (BLs). However, a major drawback is the use of a relatively high concentration of cryoprotectants, and the higher incidence of MZT(monozygotic twinning). Therefore, we analyzed perinatal incidence after 13 weeks of gestation including the rate of MZT in infants born after vitrified BL. DESIGN: Retrospective analysis. MATERIALS ANDMETHODS: Perinatal outcome were summarized for all patients who had vitrified BL transfer cycles between 2000 and 2010. Vitrification involved the exposure DMSO and EG during the cooling step, and 0.25/0.5 M sucrose solution for warming. The blastocoelic cavity was collapsed with laser pulse, prior to vitrification. After warming, zona hatching was carried out. MZT was defined that the number of FHB was more than that of embryos transferred. RESULTS: A total of 8960 vitrified BLs from 5434 cycles were warmed and 8432 survived (94.1%). In 5347 transfers, 2568 resulted in pregnancy (48.0%). A total of 7532 vitrified BLs were transferred and 2882 were implanted (38.3%). A total of 1751 children(899boys & 852girls) were born in 1533 deliveries. Forty one clinical pregnancies were confirmed as MZT(2.7%). Thirty three cases had either congenital birth defects or perinatal complications (1.9%), including six chromosomal abnormalities (two 18, four 21 trisomy), six multiple anomalies, one stillbirth due to hydropus, four stillbirths of unknown causes, one anencephaly, one spina bifida, nine congential heart malformations, one esophageal and one biliary duct obstruction, one Cornelia De Lange, and one Treacher Collins syndrome. CONCLUSION: The perinatal results of 1517 deliveries of 1735 babies, the incidence rate of MZT (2.7%) and rate of congenital defect and neonatal complication (1.9%) that were both similar to fresh BL transfer as we reported previously (2.3% & 2.0%), confirm the safety of vitrified BL program. Also, the high implantation rate encourages us to establish single BL transfer.