P–774 Clinical effectiveness of elective single versus double blastocyst transfer in women aged 36 years or older
Authors: Cai H , Mol B W , Gordts S , Wang H , Shi J 
Published: August 2021

Abstract

Study question
If the elective single-blastocyst transfer (eSBT) strategy can be applied to women aged 36 or older.

Summary answer
In women ≥36 years old with at least two blastocysts, eSBT increased cumulative livebirth rate (LBR) while minimizing twins compared with double blastocyst transfer (DBT). What is known already: In young women with a good prognosis, eSBT policy is an accepted strategy to maintain LBR while decreasing multiple gestation. However, in many areas of the world DBT is still applied in older women.

Study design, size, duration
We performed a retrospective cohort study of 429 women aged ≥36 years or older who received IVF ovarian stimulation cycles between Jan 2015 and Oct 2018 and who had at least two blastocysts. Women were followed up until Oct 2020 for their fertility outcomes including cumulative live birth and multiple pregnancies. The study was performed at the Northwest Women and Children’s Hospital, Xi’an, China.

Participants/materials, setting, methods
Out of 429 women, 240 underwent a fresh cycle of eSBT and 189 DBT. The subsequent frozen-thawed embryo transfer cycles were a combination of single- and double- blastocyst transfers, more commonly the latter. Analysis was stratified for patients in age groups 36–37, 38–39 and ≥40 and quality of the blastocyst transferred, as graded by morphological examination. Outcomes were the LBR in the fresh cycle, cumulative LBR and multiple rate after fresh and frozen embryo transfers.

Main results and the role of chance
The cumulative LBR was 74.2% (178/240) for eSBT versus 63.0% (119/189) for DBT (OR = 1.69, 95%CI 1.12–2.56), irrespective of female age. The multiple rate was 9% (16/178) after eSBT versus 29.4% (35/119) after DBT (P- value &lt; .001). The total number of children born was 194 after eSBT versus 154 after DBT. Stratified by female age, the cumulative LBRs in women aged 36–37 (78.9 vs 70.5%), 38–39 (68.9 and 61.1%) and ≥ 40 years (59.3 and 47.5%), were higher after eSBT compared with DBT, however, the differences did not reach statistical significance in each subgroups. LBRs in the fresh cycles were comparable for patients with eSBT compared with DBT (52.1% vs. 52.4%, OR = 0.99, 95%CI 0.68–1.45). In women &lt; 40 years, DBT resulted in a small non-significant increase in LBR in the fresh transfer (63.2% vs. 61.2%, 95%CI=0.64–1.85, 36–37 years; 48.1% vs. 41.0%, 95%CI=0.64–2.80, 38–39 years) at the expense of a marked increase in twinning rate (0–5.4% vs. 31.7–34.6%). For women ≥40 years, no significant differences were observed in the LBR (37.0% vs 45%, 95%CI 0.47–4.07) or twinning rate (0 vs 7.7%) between eSBT and DBT group. The findings persisted with and without accounting for quality of the blastocyst transferred.

Limitations, reasons for caution
This study is limited by its observational character.
Wider implications of the findings: In women ≥36 years with two blastocysts, eSBT should be the preferred treatment which maximizes the cumulative LBR for a decrease in the rate of multiple pregnancies.

Trial registration number
Not applicable