Adding a low‐quality blastocyst to a high‐quality blastocyst for a double embryo transfer does not decrease pregnancy and live birth rate

Abstract

Introduction The effect of embryo quality on clinical outcomes of assisted reproductive technology following a double transfer is not well defined, with some studies suggesting that a low‐quality embryo transferred with a high‐quality embryo decreases the live birth rate (LBR), compared with transferring a single high‐quality embryo. Our study examined whether the quality of a second blastocyst transferred affects the outcome, controlling for the number of the available high‐quality blastocysts (HQB). Material and methods A historical cohort study of 2346 fresh blastocyst transfers in a single fertility clinic between 2013 and 2019. The main outcomes were pregnancy, miscarriage, live birth, and multiple gestation rates. Outcomes were compared between single embryo transfers with a high‐quality blastocyst (SET‐H), double embryo transfers with two HQBs (DET‐HH), and transfers with one high‐quality and one low‐quality blastocyst (DET‐HL). Outcomes were also assessed between SET and DET when only low‐quality blastocysts were available. Results With one HQB available, DET‐HL increased LBR (adjusted odds ratio [OR] 1.65, 95% CI 1.09‐2.49) compared with SET‐H, but increased multiple gestation rate (aOR 23.1, 95% CI 3.0‐177.6). With two HQBs available, DET‐HH was associated with a higher LBR (aOR 1.62, 95% CI 1.28‐2.04) and lower miscarriage rate (aOR 0.56, 95% CI 0.40‐0.80), but very high twin rate (aOR 49.8, 95% CI 24.3‐102.1) compared with SET‐H. A SET‐H with at least one or more HQB available to freeze, compared with a SET‐H with no other HQB available, had a higher LBR (aOR 1.69, 95% CI 1.17‐2.45). When there were no HQBs available, compared with SET‐L, a DET‐LL had a higher live birth (aOR 3.20, 95% CI 1.78‐7.703) and twin rate (aOR 3.72 × 10¹⁰) and a lower miscarriage rate (aOR 0.24, 95% CI 0.10‐0.58). Conclusions When there is one HQB available, transferring an additional low‐quality blastocyst would only slightly increase the LBR, but significantly increase the twin rate, therefore SET should be recommended. When two or more HQBs are available, SET‐H would have a reasonably good chance of success without the very high twin rate associated with DET‐HH. DET‐LL when compared with SET‐L, would increase the LBR, but increase the risk of multiple gestation.