The impact of laser-assisted hatching on the outcome of frozen human embryo transfer cycles

Abstract

SummaryBiochemical modifications of zona pellucida (ZP) result in zona hardening. Zona hardening (ZH) is induced by several factors such as advancing maternal age, in vitro culture conditions and cryopreservation and adversely effects implantation. The objective of the clinical study was to determine whether or not laser-assisted hatching (LAH) applied on day 3 frozen embryos improves the outcome of frozen embryo transfer (FET) cycles in patients with recurrent implantation failure and/or advanced female age. In total, 413 patients of different ages with recurrent implantation failure (maximum three cycles) were involved into the study. Patients were allocated randomly into LAH and control groups. On the day of FET, after thawing and just before FET, the ZP was thinned using a laser system. In the control group no treatment was applied on frozen embryo before transfer. The main outcome measures were clinical pregnancy rate. Overall, the results indicate a tendency that LAH increased (P = 0.08) clinical pregnancy. However, for patients older than 37 years, LAH increased pregnancy rates significantly (P = 0.03). In the LAH and control groups, the age of patients and the number of transferred embryos influenced pregnancy rates (P = 0.01). For patients older than 37 years, no effect of number of transferred embryos was detected (P = 0.14). The incidence of multiple pregnancies also increased in the LAH group (P = 0.01). In conclusion, in older woman, to overcome the negative effect of zona hardening, LAH could be performed on frozen embryos as a routine strategy before FET in frozen cycles in order to increase the possibility of pregnancy formation.

Effects of three-area laser-assisted zona thinning in 8-cell human embryos on pregnancy outcomes in vitro fertilization

“…For this reason, FT embryos have been considered prime candidates for AH [ 2 ], but the benefits of AH in FT embryos have been controversial. Two recent studies showed LAH to have positive effects on clinical pregnancy outcomes [ 9 10 ]. The present study also showed that LAH could significantly increase the pregnancy rate in FT ET cycles.…”

“…Regarding older women, a recent meta-analysis suggested that AH has little effect on the clinical pregnancy rate in patients with an advanced maternal age of 38 years or older [ 2 ]. However, Kanyo et al [ 10 ] reported that LAH significantly increased the pregnancy rate in patients older than 37 years. In this study, LAH did not have different effects on older and younger patients.…”

Thinning and drilling laser-assisted hatching in thawed embryo transfer: A randomized controlled trial

“…The stimulation protocols, oocyte recovery, and ET techniques were used as previously described [315]. Briefly, all patients were treated with controlled ovarian stimulation by a gonadotropin-releasing hormone antagonist protocol using a starting dose of 225 IU of recombinant follicle-stimulating hormone (rFSH) (Gonal F; Merck Serono, Darmstadt, Germany).…”

“…Cryopreservation of embryos helps increase the cumulative pregnancy rate in in vitro fertilization (IVF) cycles [1]. However, embryo cryopreservation can cause zona pellucida (ZP) hardening, which leads to impaired embryo hatching and a lower implantation rate [23]. Scanning electron microscopy data have shown that the number and size of holes in the ZP of vitrified embryos were smaller than in fresh ZPs [4].…”

“…One of the reasons for this is that vitrification may impair hatching of the embryo. Theoretically, assisted hatching (AH) may facilitate the hatching process and subsequently increase the implantation rate [236]. Many authors have suggested that perforating or thinning the ZP of frozen-thawed embryos by AH facilitates embryonic implantation by making it easier for the embryo to exit the surrounding ZP [78].…”