The effects of number and quality of transferred blastocysts and female
age on pregnancy outcomes in frozen-thawed cycles: a retrospective study
Abstract
Abstract Objective To evaluate the effects of number and quality of
transferred blastocysts and female age on pregnancy outcomes. Design A
retrospective study. Setting Two IVF centers. Population Women
undergoing first blastocyst transfer in frozen-thawed cycles. Methods
6096 frozen-thawed blastocyst transfer cycles were divided into five
groups based on blastocyst number and quality and three groups according
to female age. Main Outcome Measures Implantation rate (IR), clinical
pregnancy rate (CPR), multiple pregnancy rate (MPR), live birth rate
(LBR) and neonatal characteristics. Results Female age, quality and
number of transferred blastocysts had significant effects on pregnancy
outcomes. IR, CPR and LBR of the same blastocyst transfer groups
decreased gradually with age. Increasing the transferred number of same
grade blastocysts did not obviously increase CPR and LBR, however, it
significantly increased MPR. For double blastocyst transfer, the
better-quality the transferred blastocysts were, the higher the IR, CPR,
MPR and LBR were. Singleton group had the best neonatal characteristics
followed by dizygotic twins and monozygotic twins. There was a positive
correlation between sex ratio and the proportion of good-quality
blastocysts, and the difference was significant between good-quality and
poor-quality blastocyst groups (1.35 vs 0.98, P/CI = 0.002/1.123-1.687).
Conclusions Selective single good-quality blastocyst transfer may serve
as an effective embryo transfer strategy to reduce MPR while maintaining
LBR and obtain good pregnancy outcomes, but, the strategy may result in
an unbalanced sex ratio of newborns. Funding None. Keywords: Blastocyst
transfer, age, multiple pregnancy, live birth rate, neonatal
characteristics.