Abstract
Background: Zona pellucida(ZP)hardening caused by prolonged in vitro culture and exacerbated by the freeze–thaw process making ZP hatching difficult; In theory, assisted hatching may facilitate the hatching process and have the potential to increase implantation and/or pregnancy rates in frozen embryo transfer (FET) cycles. However, a number of studies have shown controversial results on the clinical benefit of laser-assisted hatching (LAH) in FET cycles. This study firstly investigated the efficacy and safety of LAH using vitrified-thawed embryos with different post-thaw culture duration in FET cycles.Methods: Data from the center’s IVF database were retrospectively analyzed, only embryos thawed for the first FET cycle of each ovarian pick-up were eligible for this study, and only cycles in which at least one embryo was available for transfer were included in the present study. Finally, a total of 1225 infertile couples who underwent 1225 FET cycles between July 2013 and March 2015 were analyzed in this study. According to the duration of post-thaw culture in FET cycles, these patients were allocated to three subgroups: the short culture (4-5 h) group (LAH, n=205; control, n=201), overnight culture (20-24 h) group (LAH, n=197; control, n=203), and blastocyst culture (44-48 h) group (LAH, n=210; control, n=209), respectively.Results: In the short culture(4-5 h) subgroup, no statistically significant differences were found related to the implantation, clinical pregnancy and live birth rates between the two groups (28.0% versus 27.8%, 38.0% versus 36.8%, and 30.7% versus 30.3%, respectively, P＞0.05). When the perinatal outcomes of two groups were compared, there was no significant difference in the gestational weeks (37.96±2.23 versus 37.59±2.35, P＞0.05), birth weight (2.70±0.56 versus 2.82±0.62, P＞0.05), as well as the preterm birth (15.4% versus 17.6%, P＞0.05), ectopic pregnancy (2.6% versus 1.4%, P＞0.05), and miscarriage rates (16.7% versus 16.2%, P＞0.05).In the overnight culture(20-24 h) subgroup, no statistically significant differences were found regarding the implantation, clinical pregnancy and live birth rates (29.5% versus 29.1%, 40.1%versus 37.4%, 33.0%versus 30.5%, respectively, P＞0.05).As to the perinatal outcomes, there was no significant difference in the gestational weeks (36.86±2.28 versus 35.69±2.95, P＞0.05), birth weight (2.73±0.76 versus2.62±0.52, P＞0.05), as well as the preterm birth (15.2% versus 17.1%, P＞0.05), ectopic pregnancy (3.8% versus 2.6%, P＞0.05), and miscarriage rates (13.9% versus 15.8%, P＞0.05).In the blastocyst culture(44-48 h) subgroup, the two groups did not differ significantly in the implantation, clinical pregnancy and live birth rates (56.3% versus 59.3%, 68.6% versus 66.5%, and 55.7% versus56.5%, respectively, P＞0.05).Furthermore, there were also no significant difference in the gestational weeks (38.68±2.76 versus 36.95±2.59, P＞0.05), birth weight (2.78±0.74 versus 2.72±0.59, P＞0.05), as well as the preterm birth (8.3% versus 11.5%, P＞0.05), ectopic pregnancy (2.8% versus 2.2%, P＞0.05), and miscarriage rates (16.0% versus 12.9%, P＞0.05).Conclusions: Our results suggested that LAH does not improve the clinical outcomes in FET cycles, irrespective of the duration of post-thaw culture. Though the risk of perinatal period did not increase, it is still necessary to conduct further investigations to validate the safety of LAH.
The impact of assisted hatching on live birth rates and outcomes of assisted conception: a systematic review
