Embryo transfer - cleavage stage vs blastocyst stage - a comparative study

Abstract

Introduction Inspite of several advances in in-vitro fertilisation (IVF), implantation rates (IR) remain low and only a small percentage of patients achieve pregnancy. There are various components that effect the results. The first pregnancy confirmed at the time of assisted conception involved the transfer of a blastocyst. However, due to problems faced in culturing human embryos for a period of 5 days, it became a common practice to transfer embryos at cleavage stages, i.e. day 2 or 3, despite relatively low implantation rates of 10–20%[1]. In contrast, few studies have reported unusually high implantation rates after blastocyst culture and embryo transfer [2]. Prolonged culture of human embryos has been advocated to extend the efficiency of IVF treatments by improving the choice of embryos with the utmost implantation potential [2]. Due to current progress in the choice of culture media used for IVF/intracytoplasmic sperm injection (ICSI) many clinics have been encouraged to postpone embryo transfer to day 5 [3,4]. It has been suggested that transferring embryos at the blastocyst stage rather than selection at an earlier stage without knowing their developmental capacity, might enhance the implantation rate by a better embryo selection, thereby reducing the necessity to transfer more embryos [5,6,7] . The most competent embryos reaching the blastocyst stage are selected for transfer and therefore the embryos that have arrested their development are identified and aren't transferred. It is thought that the expression of genes of human embryos is switched on around the 8-cell stage immediately before compaction [8]. Therefore, nutrient requirements of embryos are more complex media after they reach the 8-cell stage. The present study was done to determine whether transferring blastocyst-stage embryos would result in higher implantation and pregnancy rates than transferring cleavage-stage embryos. Aims and Objectives To compare implantation and pregnancy rates of cleavage stage vs blastocyst stage embryo transfer in women undergoing an in-vitro fertilization or ICSI. Background:In vitro fertilisation (IVF) is a complicated procedure, whose success depends on several factors. Besides the status of the embryo and endometrium, embryo transfer (ET) plays a key role. However, there are few prospective comparative studies in India, comparing day 3 versus day 5 embryo transfer. Aims: To compare implantation and pregnancy potential of day 3 versus day 5 embryo transfer in women undergoing an in-vitro fertilization or Intracytoplasmic sperm injection (ICSI). Settings and Design: Prospective comparative study. Material and methods: Study included 270 women from January 2014 to December 2016. After retrieval of oocytes and their fertilization, patients were randomly assigned to undergo embryo transfer either on day 3(Group A) or day 5(Group B). Demographic data, clinical profile, implantation and pregnancy rates were compared between the two groups. Statistical Analysis: Comparisons between groups were made by using Fisher's exact test or chi-square analysis. P ?0.05 was considered as significant. Results : The distribution of patients were similar between the two groups (n=135 and 135 respectively) and there was no statistically significant difference in terms of duration of infertility (p=0.208), number of oocytes retrieved (p=0.136), number of oocytes fertilized (p=0.619), and number of embryos transferred (p=1). Both the groups had statistically similar implantation rates, clinical pregnancy rates, live birth and perinatal death rates (p=0.33, p=0.272, p=0.532, and p=0.701, respectively).Conclusion: Present study demonstrates that blastocyst stage transfers have no advantages over cleavage stage transfers