Influence of delayed blastulation and expansion grade on clinical outcomes of high-quality blastocyst transfer: an analysis of 1751 frozen-thawed cycles

Abstract

The aim of the study was to compare retrospectively the extent of blastulation timing (Day 5 or later) and expansion grade to predict the ability of blastocysts to give rise to a pregnancy. Blastocysts frozen on day 5 with a lower expansion grade (group D5) or day 6 with a higher expansion grade (group D6) were included. A single embryo was thawed and transferred on day 5 after ovulation or progesterone supplementation. Differences in patient baseline characteristics, endometrial preparation and pregnancy outcomes between groups were stratified by patient age and anti-Müllerian hormone (AMH) levels. Logistic regression was used to analyse the results. A total of 617 blastocysts in group D5 and 1134 blastocysts in group D6 were assessed. Stratified analyses showed higher biochemical pregnancy, clinical pregnancy and live birth rates for patients aged less than 30 years old, and higher ongoing pregnancy rate for patients with AMH ≥ 1.1 ng/ml. For patients aged less than 30 years old, the biochemical pregnancy, clinical pregnancy and live birth rates in group D5 were higher than those in group D6.

Keywords:

• Blastocyst morphology
• blastocyst expansion
• pregnancy outcomes
• frozen-thawed transfer
• delayed blastulation
• embryo selection

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Key R&D Program of China under Grant [number 2017YFC1001603]; National Natural Science Foundation of China under Grant [number 81871214]; Guangdong Science and Technology Department ‘Overseas Master Teacher’ Project under Grant [number 005291764027]; and the Medical Scientific Research Foundation of Guangdong Province under Grant [number A2021026].