Optimal number of high-quality cleavage-stage embryos for extended culture to blastocyst-stage for transfer in women 38 years and older.

PURPOSE: We aimed to evaluate the pregnancy outcomes of cleavage-stage embryo transfers (ETs) for the first time and explore optimal number of high-quality cleavage-stage embryos for extended culture to blastocyst-stage in women of advanced maternal age (AMA).

METHODS: We retrospectively identified 1646 AMA women ≥ age 38 years for the first fresh ETs between January 2014 and December 2020 at our hospital. Double ETs were divided into three groups as follows: DET-HH (two high-quality embryos), DET-HL (one high-quality and one low-quality embryo), and DET-LL (two low-quality embryos) groups. We mainly analyzed the pregnancy outcomes of double cleavage-stage ETs with different embryo grades and blastocyst-stage ETs with different number of high-quality cleavage-stage embryos on day 3.

RESULTS: Our data indicated that the DET-HH group had significantly higher clinical pregnancy, ongoing pregnancy, and live birth rates than DET-HL and DET-LL groups ( p  < .05). For extended culture to blastocyst-stage with 2 (D3-2H), 3 (D3-3H), and 4 (D3-≥4H) high-quality cleavage-stage embryos, the D3-≥ 4H group had significantly higher ongoing pregnancy and live birth rates than D3-2H and D3-3H groups ( p  < .05). We observed that the number of high-quality embryos on day 3 was independently associated with live birth rate for blastocyst transfers (OR: 1.133, 95% CI 1.023-1.256, p  = .017). There were no significant differences in the clinical pregnancy, ongoing pregnancy and live birth rates among DET-HH, D3-2H and D3-3H groups ( p  > .05).

CONCLUSIONS: Extended culture to blastocyst-stage for transfer was safe and recommended for AMA women with ≥ 4 high-quality embryos on day 3.