Blastocyst and cleavage stage embryo biopsy for preimplantation genetic testing of the sickle cell gene in carrier couples: the experience of an IVF clinic in a developing country a retrospective study

Abstract

Introduction: Embryo biopsy is a prerequisite for preimplantation genetic testing (PGT). Although cleavage stage biopsy is very common, trophectoderm biopsy at blastocyst stage has become increasingly popular in recent times. This study describes the clinical success of PGT cycles for sickle cell anemia using both cleavage and trophectoderm biopsy in a developing country. Materials and Methods: All patients undergoing in vitro fertilization and PGT for sickle cell anemia from April 2011 to February 2017. Embryos were biopsied either on day 3 (blastomere) or day 5/6 (trophectoderm). Laser pulses (ZILOS-tk Laser) perforating the zona pellucida were followed by either blastomere aspiration from a day 3 cleavage stage embryo or trophectoderm biospy from a day 5/6 blastocyst. Embryos were vitrified awaiting subsequent thaw and transfer. After excluding homozygous hemoglobin SS embryos, frequencies of positive human chorionic gonadotrophin, clinical pregnancy, implantation rate and live birth rate were recorded for day 3 cleavage stage embryos (group A) and day 5/6 blastocysts (group B). Results: Of the 34 patients undergoing in vitro fertilization PGT for sickle cell anemia, embryos from 18 underwent day 3 blastomere aspiration (group A) whereas embryos from 16 underwent day 5/6 trophectoderm biopsies (group B). The mean patient age was 34.4 years for group A and 34.1 years for group B. A total of 131 embryos were biopsied in group A and 106 in group B. Percentages of unaffected embryos (ie, HB AA and AS) in groups A and B were 40.4% and 68.0%, respectively. Positive human chorionic gonadotrophin rates were 7.7% and 60%, clinical pregnancy rates 7.7% and 20%, implantation rates 3.7% and 32.1%, and live birth rates 3.7% and 20%, respectively. Conclusions: In this developing country, the use of trophectoderm biopsy for interrogating embryos at risk for sickle cell anemia appeared superior to blastomere aspiration at the cleavage stage for the purpose of PGT.