Assisted hatching decreases pregnancy outcomes in vitrified donor oocytes.

Objective: To evaluate the impact of assisted hatching on implantation and pregnancy rates among fresh embryo transfers using vitrified donor oocytes.

Design: Retrospective cohort study.

Setting: Twenty-nine IVF centers involved in the Donor Egg Bank United States of America database between 2015 to 2020.

Subjects: Oocyte donor recipients.

Exposure: Assisted hatching.

Main Outcome Measure(s): Rates of implantation, clinical pregnancy, spontaneous abortion, and ongoing pregnancy.

Results: Among the 2,617 embryos, 1,668 (64%) underwent assisted hatching. The biochemical pregnancy rate per transfer and clinical pregnancy rate per transfer were significantly lower for the assisted hatching group vs non-assisted hatching group (72% vs 76%, aRR 0.94, 95% CI 0.9-0.99, p<0.01 and 61% vs 66%, aRR 0.92, 95% CI 0.86-0.97, p<0.01). The assisted hatching group also had a lower ongoing/sustained pregnancy rate (57% vs 62%, aRR 0.91 95% CI 0.78-0.91, p=<0.01) compared to the non-assisted hatching group. Spontaneous abortion may be higher for the assisted hatching group compared to the non-assisted hatching group, although not statistically significant (13% vs 11%, p=0.32).

Conclusions: Assisted hatching may be associated with decreased clinical and ongoing pregnancy rates in donor oocyte cycles.