To investigate the effects of laser-assisted hatching (LAH) on clinical pregnancy outcomes and maternal and infant safety of frozen-thawed embryo transfer (FET).

A retrospective cohort study was conducted at Reproductive Center of Lianyungang Maternal and Child Health Care Hospital from January 2017 to January 2020. The clinical data of 641 FET cycles were analyzed, which were divided into the cleavage stage and blastocyst stage embryo transfer. The FET cycles of different embryo stages were divided into LAH group and Non-LAH group based on the method used with or with-out LAH. Clinical outcomes and maternal and infant information were compared using univariate analysis between LAH group and Non-LAH group. Multivariate logistic regression analysis was used to control other confounding factors and analyzed the effects of LAH on live birth rate. The primary outcome was live birth rate. Secondary outcomes included clinical pregnancy rate, implantation rate, multiple births rate, abortion rate, ectopic pregnancy rate, premature delivery rate, perinatal maternal complications and neonatal outcomes.

The characteristics of patients were not significantly different between the two groups (P>0.05). In cleavage-stage embryo transfer group, there were no significant differences in clinical outcomes between LAH group and Non-LAH group (P>0.05). In the blastocyst embryo transfer patients, the clinical pregnancy rate [71.2% (109/153)], the implantation rate [61.2% (126/206)] and the live birth rate [66.7% (102/153)] in LAH group were significantly increased compared with the Non-LAH group [56.2% (59/105), P=0.013; 46.4% (65/140), P=0.007; 48.6% (51/105), P=0.004] and the rates of multiple pregnancy, abortion, ectopic pregnancy and preterm birth were similar between the two groups (all P>0.05). There were no statistical differences in perinatal maternal complications and neonatal outcomes between LAH group and Non-LAH group (all P>0.05). Multivariate logistic regression analysis showed that LAH had no effect on the live birth rate of FET patients at cleavage stage, but could increase the live birth rate of FET patients at blastocyst stage (OR=2.656, 95% CI=1.505-4.689, P=0.001).

LAH can improve the clinical pregnancy outcomes in FET at blastocyst stage, but there was no benefit to improve the pregnancy outcomes in FET cycles at cleavage stage with LAH. In our results, no adverse effect of LAH on perinatal maternal and infant safety has been observed.

Blastocyst; Frozen-thawed embryo transfer; Laser-assisted hatching; Cleavage embryo; Clinical outcomes; Maternal and fetal security