P-781 Elective single cleavage-stage embryo transfer in IVF patients with suboptimal ovarian response is not detrimental to cumulative pregnancy and reduces multiple pregnancy rates
Authors: Paffoni A , Cesana S , Kunderfranco A , Wyssling H , Bianchi M.C 
Published: June 2022

Abstract

Study question
To compare elective single embryo transfer (eSET) with double embryo transfer (DET) in patients with suboptimal response to ovarian stimulation in terms of pregnancy rates.

Summary answer
Elective single embryo transfer in patients with suboptimal response to ovarian stimulation is not detrimental to cumulative pregnancy and delivery rates.

What is known already
Even though higher-order pregnancies in in vitro fertilization (IVF) programs have dropped significantly in recent years, the incidence of twin pregnancies is currently not negligible. The greatest efforts to promote eSET have been made in the IVF population with a good prognosis but results obtained in this population can hardly be extrapolated to patients with lower chances of success, such as those with low oocyte yield. Although still under discussion, it has been suggested that in patients with poor or suboptimal response to ovarian stimulation, eSET could achieve acceptable cumulative live birth rates with negligible risk of twin pregnancy.

Study design, size, duration
A matched case-control pre and post intervention study including IVF patients with poor or sub-optimal response to ovarian stimulation (≤9 oocytes) receiving a double embryo transfer (2016-2018) or elective single embryo transfer (2018-2020). Matching was performed 1:1 for female age (±18 months), AMH ≥1.2 or &lt; 1.2 ng/ml and number of previous cycles. A sample size of 215 patients per group was foreseen to obtain ±5% variability of the main outcome (clinical pregnancy rate per cycle).

Participants/materials, setting, methods
A strict policy regarding single embryo transfer was introduced in our clinic from September 2018 to reduce twin pregnancy rates independently from ovarian response or embryo quality. Couples undergoing standard IVF or ICSI with ≤9 oocytes and at least 2 viable embryos were divided in two groups and matched for main variables known for influencing results: pre-intervention with DET (controls) and post-intervention with eSET (cases). In both groups, cryopreserved supernumerary embryos were always transferred individually.

Main results and the role of chance
A total of 463 patients with at least 2 viable embryos undergoing fresh embryo transfer after the recovery of 2 to 9 oocytes were retrospectively evaluated and, according to matching criteria, 212 cases (eSET) and 212 matched controls (DET) were included for data analysis. The cumulative clinical pregnancy rate per cycle was the same in the two groups (26%, 95%CI: 20-32%) with a crude OR = 1.00 (95%CI: 0.65-1.54), p = 1.00 and a mean female age of 37.4 and 38.0 years, respectively. The mean number of mature oocytes was 4 ±2 in both groups. Live birth rate was similar in cases and controls (22% and 21%, respectively) while twin pregnancies were significantly reduced in women receiving single embryo transfer (18% versus 0%, p = 0.008). Women receiving eSET were more likely to undergo a subsequent frozen embryo transfer (26% versus 14%, p = 0.002). Considering the main confounding factors, a binomial logistic model indicated that the cumulative clinical pregnancy rate was not significantly affected when a single embryo transfer was performed in women recovering up to nine oocytes. Similar results were obtained comparing cases and controls within subgroups: 2-4 or 5-9 oocytes; &lt;35 or 35–39 or &gt; 39 years female age).

Limitations, reasons for caution
This study does not have the statistical power to highlight small differences between the two groups. It was conducted on a specific population of women with 9 or less oocytes therefore results cannot be generalized to other populations, particularly those with a better or poorer prognosis.

Wider implications of the findings
eSET results are mainly based on good prognosis couples. Despite a trend for better success after fresh DET, cumulative results are not affected by eSET at the cleavage stage with significantly reduced incidence of twins and moderate delay in time to pregnancy also in poor/suboptimal responders.

Trial registration number
not applicable