Analysis of different clinical and biological Factors affecting Pregnancy Rate in frozen-thawed embryo transfer

Abstract

Frozen embryo transfer (FET) is an important part of present-day IVF/ ICSI treatment. There is limited understanding of the factors affecting success rates after FET. The aim of this work to study the Clinical and laboratory factors which affect clinical pregnancy rate after frozen—thawed embryo transfer.Study design: This is three-center prospective study. Analysis was carried out on 150 consecutive FET cycles during the period from 2011 - 2015. The primary outcome was clinical pregnancy per cycle. We assessed the independent effect on clinical pregnancy of the following variables: female age, female age at embryo freezing, BMI, primary versus secondary infertility, cause & duration of infertility, LH/FSH ratio, protocol of fresh cycle, serum estradiol level before Human Chronic Gonadotropin (HCG) at fresh cycle, sperm source (testicular or ejaculated), day of freezing, pregnancy in the fresh cycle, storage duration of embryos, cause of, thawing method as well as number of thawed transferred embryo (s).Main results: Pregnancy rate in FET was 31%. Pregnancy rate was 21.6% in patient younger than 30 years old at fresh cycle with RR 2.31 with CI (1.72-7.37). Patients of age at FET more than 35 years to have positive outcome 9.4% of FET with 95% CI= (1.72-7.37).There was absolute risk increase of 2.91 between the two BMI groups (>=30 & 3 thawed embryos was transferred (odds ratio (OR) 0.34 95% confidence interval (CI) (0.12-0.97).Conclusion: Increased number of transferred thawed embryos is associated with increased clinical pregnancy; Age, BMI, cause of infertility, semen parameters, pregnancy at fresh cycle, endometrial thickness on the thawed embryo transfer day and cause of freezing. Number of transferred thawed embryos affected independently the clinical pregnancy rate in FET.