Comparison of the impact of laser-assisted hatching on fresh cleavage and blastocyst embryo transfer and association with pregnancy outcomes

Assisted hatching (AH) techniques can improve live birth (LB) and clinical pregnancy (CP) rates. Since there are limited data regarding this subject, we investigated the impact of laser-assisted hatching (LAH) on fresh embryo transfer (ET) and association with pregnancy outcomes in unselected patient population.This retrospective study included the fresh ETs performed at our center between April 2010 and April 2019. Among 3.782 fresh ETs, 3.286 underwent LAH (n=1.583 at cleavage stage and n=1.703 at blastocyst stage) while 496 underwent non-assisted hatching (NAH) (n=213 at cleavage stage and n=283 at blastocyst stage). The ETs were performed at the blastocyst or cleavage stages, and single or double embryos were transferred. LB rate was the primary outcome, while secondary outcomes were the pregnancy test, monozygotic twinning (MZT), and CP rates.The LAH and NAH groups showed similar LB, pregnancy test, CP, and MZT rates at cleavage and blastocyst stages. On the other hand, LAH significantly affected LB rates at the blastocyst stage (20.6% at blastocyst stage vs. 16% at the cleavage stage, p=0.001).In conclusion, LAH does not improve reproductive outcomes of fresh blastocyst-stage and cleavage-stage ETs. However, LAH significant impacts LB rates in the blastocyst stage than the cleavage stage.