Risk of major congenital anomalies after assisted hatching: analysis of three-year data from the national assisted reproduction registry in Japan

Objective: To assess perinatal risk of major congenital anomalies in children born after embryo transfer with assisted hatching (AH).

Design: Retrospective cohort study.

Setting: Not applicable.

Patient(s): Cycles registered from 2010 to 2012 and conceived via single-embryo transfer were included for the analysis. Live births, still births after 22 weeks of gestation, and selectively terminated cases because of congenital anomalies were included.

Intervention(s): None.

Main outcome measure(s): Major congenital anomaly.

Result(s): AH was performed in 35,488 cycles among 72,125 included cycles (49.2%). A total of 1,046 major congenital anomalies (1.4%) were identified (1.36% in AH group vs. 1.50% in non-AH group). Overall risks for major congenital anomalies were not significantly different between AH and non-AH groups adjusting for maternal age, calendar year, fetal sex, embryo stage at transfer, and status of cryopreservation. There were 1,009 cases of twins (1.5%) and 10 cases of triplets (0.015%) among all included cycles. No specific organ system demonstrated significant association between AH and non-AH groups. Subgroup analysis demonstrated no significant association between AH and non-AH groups in intracytoplasmic sperm injection cycles or in vitro fertilization in fresh cycles. Similar nonsignificant association was observed between early-cleavage or blastocyst stage at transfer in frozen-thawed cycles.

Conclusion(s): Our results suggest that AH alone does not increase the risk of major congenital anomaly.