P-711 Female age at embryo creation and embryo transfer do not impact the ongoing pregnancy rates in single euploid frozen embryo transfers
Authors: Lawrenz B , Kalafat E , Ata B , Del Gallego R , Melado L , El Khatib I , Bayram A , Fatemi H 
Published: July 2024

Study question

Which factors influence the ongoing pregnancy rate in single euploid frozen embryo transfer (seFET) cycles?

Summary answer

Ongoing pregnancy rates in seFET cycles are significantly influenced by parity, BMI, embryo quality, trophectoderm biopsy day and endometrial preparation, but not by female age.

What is known already

The probability of a pregnancy is influenced by several factors and female age is the major determinant as the ovarian reserve decreases and embryo aneuploidy increases with age. Preimplantation genetic testing for aneuploidy and embryo selection was considered to mitigate the effect of female age on ART treatment outcomes by selecting euploid embryo(s) for embryo transfer (ET). Previously published data point to a decline in pregnancy rates with increased maternal age even when a euploid embryo is transferred. However, other factors besides embryo ploidy might play a role in the chance of achieving an ongoing pregnancy.

Study design, size, duration

Retrospective study, including 1923 women who underwent a seFET between 04/2017 and 08/2023. Patients’ (age at oocyte-pick-up and seFET, BMI, parity, endometrial preparation type) and embryo characteristics (Day of biopsy, embryo quality (EQ)) were considered for the analysis. Ongoing pregnancy was defined as viable pregnancy beyond 12 weeks of gestation.

Participants/materials, setting, methods

Women, undergoing a seFET either in a true natural cycle (NC) t or in a hormonal replacement cycle (HRT). Only cycles with embryos being biopsied on day 5 or day 6 and a known outcome of the cycle were included.

Main results and the role of chance

There were 990 (51.48%) ongoing pregnancies among 1923 included transfers. The ongoing pregnancy rates were 51.8%, 47.4%, 52.3% and 52.8% for women aged ≤35, &gt;35 to ≤ 37, &gt;37 to ≤ 40, and &gt;40 years-old at seFET, respectively. Cochrane Armitage test did not show a significant trend for decreasing pregnancy rates with increasing female age at OPU (P = 0.679) or at transfer (P = 0.609). Multivariable regression analyses showed primiparous, and multiparous women were more likely to have an ongoing pregnancy compared to nulliparous women (OR: 2.96, 95%CI:2.22-3.94 and 2.73, 95%CI:2.10-3.55, respectively, P &lt; 0.001 for both) and those who had a natural endometrial preparation (OR: 1.53, 95%CI: 1.24-1.88, P &lt; 0.001). Transfers with good quality embryo had higher ongoing pregnancy rates compared to those who had a fair quality embryo (OR: 2.0, 95%CI: 1.37-2.91, P &lt; 0.001). Being overweight or obese at the time of transfer were associated with lower ongoing pregnancy rates compared to normal weight (OR: 0.71, 95%CI: 0.56-0.89, and 0.68, 95%CI: 0.52-0.88, respectively, P = 0.003 for both). Age categories at the time of transfer did not show a significant effect on ongoing pregnancy rates in multivariable analyses (P &gt; 0.05 for all) and there was no significant interaction between age at OPU and embryo quality categories either (P = 0.881 and 0.601).

Limitations, reasons for caution

The retrospective design of the study is a limitation.

Wider implications of the findings

This analysis did not confirm the otherwise reported negative impact of female age on the outcome of seFET cycles. Outcomes are significantly influenced by BMI, parity, EQ-related factors as well as the endometrial preparation. As BMI and endometrial preparation can be influenced, the adequate choice might improve seFET outcomes.

Trial registration number

not applicable