Blastocoele re-expansion time in vitrified-warmed cycles is a strong predictor of clinical pregnancy outcome.

ABSTRACT

AIM: To assess the predictive value of blastocoele re-expansion time in clinical pregnancy outcome in vitrified-warmed cycles. METHODS: Data on 468 single vitrified-thawed blastocyst transfer cycles (in patients aged <38 years) carried out from January 2012 through December 2012, at the Reproductive Medicine Center, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, were analyzed. Vitrified-warmed blastocysts were divided into three groups according to blastocoele re-expansion time group A, <1 h; group B, 1-2 h; and group C, >2 h, and the clinical pregnancy outcomes (i.e. live birth rate, miscarriage rate and occurrence of singleton pregnancies) compared between the groups. RESULTS: Significant differences were observed in the implantation/clinical pregnancy rate between groups A, B and C (70.10%, 51.76% and 28.74%, respectively, P < 0.01). There was a significant linear decline in this rate with increasing blastocyst re-expansion time. The rate of miscarriage also tended to increase with increasing blastocyst re-expansion time, but the difference was not statistically significant (P > 0.05). Of the pregnant patients, no significant difference was observed in the rates of monozygotic twins and ectopic pregnancy between the three groups. For the newborns, similar live birth, low-birthweight and premature delivery rates were observed between the groups. CONCLUSIONS: Timing of blastocoele re-expansion in vitrified-warmed cycles is a strong predictor of clinical pregnancy outcome. The faster the re-expansion of the blastocoele, the higher the developmental potential of the blastocysts.