BLASTOCYST FORMATION IS NOT AFFECTED BY FEMALE OBESITY: A MORPHOKINETIC STUDY

Abstract

To determine whether the embryo cleavage pattern and the rate of blastocyst formation differs between normal weight and obese women undergoing in vitro fertilization (IVF) with ICSI (intracytoplasmic sperm injection). This is a retrospective cohort study performed from January 2016 to May 2020 in IVIRMA-Valencia. A total of 3,316 ICSI cycles from 2,822 women were included, with 1,251 cycles belonging to the Preimplantation Genetic Testing (PGT) program. Patients were grouped according to their body mass index (BMI).Underweight was defined as a BMI < 18.5 kg/m2 (n = 173 cycles from 140 women), normal weight as a BMI of 18.5–24.9 kg/m2 (n= 2,339 cycles from 1,989 women), overweight as a BMI of 25–29.9 kg/m2(n = 643 cycles from 548 women) and obesity as a BMI of >30 kg/m2 (n =161 cycles from 145 women).All embryos were grown in vitro until the fifth or sixth day in a time-lapse system - EmbryoScope, EmbryoScope Plus (Vitrolife) and Geri Plus (GeneaBiomedx) - and its development was assessed on an external computer with a specific software for the purpose. There were no differences in sperm parameters or male age among the four BMI groups. Underweight women were l year or less younger than the other three groups. The percentage of women with polycystic ovary syndrome was higher but not significantly different in the obese group. Indications for PGT do not differ among groups .The number of oocytes retrieved or mature oocytes microinjected was significantly higher in the obese group than in the normal weight group. However, fertilization rates and number of embryos transferred were similar in the four BMI groups. A higher percentage of surplus embryos for freezing was observed in the underweight group when compared to normal weight women. All the embryos were transferred or frozen in blastocyst stage. Despite an initial slower pattern of embryo development, the final blastocyst formation rate in day 5 or in day 5 plus day 6 did not differ in obese women when compared to the other BMI groups. Moreover, embryo quality, based on the evaluation of inner cell mass and trophectoderm in both days of blastocyst development was similar across BMI groups. The same was observed with respect to the pattern of development and arrest up to blastocyst formation and the different categories of full, expanded and hatching blastocysts. Blastocyst formation is not affected by female BMI.