Artificial shrinkage of blastocoel using a laser pulse prior to vitrification improves clinical outcome

Abstract

Purpose Blastocysts contain a large amount of fluid in the blastocoel, which may pose a risk for ice crystal formation during vitrification. This study aimed to evaluate the effectiveness of laser-induced artificial shrinkage of blastocoel before vitrification on clinical outcome. Methods Patients were divided into two groups: a control group with untreated, expanded blastocysts (n = 115) and a study group with blastocoel artificially eliminated by a laser pulse prior to vitrification (n = 309). Blastocyst survival, clinical pregnancy, and implantation rates were compared. Result(s) The survival rate was significantly higher in the study group compared with the control group (97.3 and 74.9 %, respectively; p > 0.01). The clinical pregnancy and implantation rates of the study group were significantly higher (p < 0.01) than that of the control group (clinical pregnancy, 67.2 vs. 41.1 %; implantation, 39.1 vs. 24.5 %. Conclusion(s) This study demonstrated that the removal of blastocoel fluid before vitrification by laser pulse of in vitroproduced human blastocysts significantly improves blastocyst survival, clinical pregnancy, and implantation rates.

Laser collapse performance in blastocysts applied before vitrification

“…Several papers whose authors experimented the application of the laser collapse technique in expanded blastocysts demonstrated its efficiency, with improvement in survival rate, pregnancy rate and implantation rate, reducing cancellations of transfers after thawing. 12,20,31 On the other hand, in the research conducted by Marcos et al, 32 the authors affirm that the collapse reduced the implantation potential of the transferred blastocysts. They reported that the collapse could act adversely in the implantation, either because it affects the quality of the embryo or by directly reducing its implantation capacity resulting in lower rates of clinical pregnancy.…”

“…1,5,7,9 The first pregnancy obtained by transfer of frozen and thawed embryos was reported by Trouson and Mohr in 1983 and since then, the cryopreservation of embryos has been used as standard procedure in human reproduction clinics. [10][11][12] Thus, three main methods of cryopreservation have been employed: slow freezing, ultra fast freezing and vitrification.…”

“…The transfer of blastocysts obtained on this way, has become promissory for increasing pregnancy rates. 12 On the other hand, the technique of embryo vitrification of blastocysts encounters an important limitation. Blastocysts present an internal cavity (blastocele) composed mainly of water that can therefore form ice crystals when the temperature is reduced and can cause internal cell mass and trophectoderm damage.…”

“…4 In order to overcome this problem many researchers presented methods for obtaining collapse of the blastocele prior to vitrification, with purpose of increasing the success of the technique. 12,[18][19][20][21] The collapse of blastocysts can be induced by mechanical means such as repeated pipetting with micropipettes of different diameters or by drilling the blastocyst using micro needles of different calibers. 19 Recently, the directed laser pulse was proposed as an alternative to mechanical collapse, and its use is currently widespread.…”

Effect of different artificial shrinkage methods, when applied before blastocyst vitrification, on perinatal outcomes

“…All these AS methods have been shown to improve blastocyst survival rate, implantation rate and pregnancy rate [7, 9, 11, 12, 17, 18]. However, only a few studies focused on the comparison of these AS methods when applied prior to vitrification.…”