Blastocyst formation is similar in obese and normal weight women: a morphokinetic study

Abstract

STUDY QUESTION Does the embryo cleavage pattern and rate of blastocyst formation differ between normal weight and obese women undergoing IVF? SUMMARY ANSWER Embryo morphokinetic development, final blastocyst formation rate and blastocyst morphology do not differ between obese and normal weight women. WHAT IS KNOWN ALREADY Female obesity has been related to impaired IVF outcomes. Although the mechanisms responsible for this detrimental effect are thought to include impaired oocyte and embryo quality and reduced endometrial receptivity, they are yet to be confirmed. Embryo quality has been commonly assessed using static morphological criteria. Only three studies have analysed the progress of embryos up to the blastocyst stage in women with elevated BMI, but they have used small samples of patients or have obtained contradictory results. STUDY DESIGN, SIZE, DURATION This retrospective, cohort study, was performed from January 2016 to May 2020. A total of 3316 ICSI cycles from 2822 women were included, of which 1251 cycles were part of a preimplantation genetic testing programme. In total, 17 848 embryos were analysed. PARTICIPANTS/MATERIALS, SETTING, METHODS This study reports on the IVF cycles of infertile women, with a known BMI, who underwent ICSI and whose embryos were grown until the fifth/sixth day of development in a time-lapse system. Patients were grouped as follows. Underweight was defined as a BMI <18.5 kg/m2; normal weight was a BMI of 18.5–24.9 kg/m2; overweight was a BMI of 25–29.9 kg/m2; and obesity was a BMI of ≥30 kg/m2. Embryo development was assessed on an external computer with analysis software. MAIN RESULTS AND THE ROLE OF CHANCE Despite an initial slower pattern of embryo development, the blastocyst formation rate on day 5 or on day 5 plus day 6 did not differ in obese women with respect to the other three BMI groups. Moreover, based on the evaluation of inner cell mass and the trophectoderm on both days of blastocyst development, embryo quality was similar across the BMI groups, as were the pattern of development and arrest up to blastocyst formation and the distribution of the categories of full, expanded and hatching blastocysts. LIMITATIONS, REASONS FOR CAUTION Limitations include the retrospective analysis of data, the use of BMI as the only parameter to define normal/abnormal female body weight, and the lack of complete information about clinical outcomes. WIDER IMPLICATIONS OF THE FINDINGS Blastocyst formation and embryo morphokinetics are not affected by female obesity, and the poorer IVF outcomes described for such women are probably due to deficient endometrial receptivity. The role of endometrial progesterone exposure on the day of embryo transfer should be analysed in future studies as a possible determining factor. STUDY FUNDING/COMPETING INTEREST(S) No external funding was used and there are no competing interests. TRIAL REGISTRATION NUMBER N/A.

A relationship between progesterone, maternal body weight, and offspring sex following the frozen/thawed single embryo transfer.

“…Other studies suggest that high BMI is not associated with the number or proportion of aneuploid, mosaic, or euploid embryos in this large cohort of patients undergoing IVF with PGD/PGS, implying that the potential adverse effect of excess weight on reproductive outcomes was independent of the ploidy status of the embryo cohort (14). This was also con rmed in the retrospective cohort study of 3,316 ICSI cycles where authors showed that blastocyst formation and embryo morphogenetics were not affected by female obesity, suggesting that the poorer IVF outcomes for such women are probably due to low endometrial receptivity (15). On the contrary, a higher BMI was not favourable for forming high-quality embryos in the ICSI cycle ( 16).…”

“…In the present study, women with higher PRG levels were more likely to give birth to a girl, implying that perhaps the role of endometrial PRG exposure on the day of embryo transfer should be considered as a determining factor of implantation in this group of patients (15). Both PRG supplementation during the luteal phase and early pregnancy improve the number of live births after frozen embryo transfer (12,21,22).…”

BMI and miscarriage after IVF

“…In contrast, in the study of 1889 infertile couples by Kim et al [3], obese patients presented a higher blastocyst formation rate than their normal weight counterparts, hence representing opposite findings. More recently, Bellver et al [40 ▪ ] morphokinetically evaluated all the embryos obtained from ICSI cycles in 2,882 women, including 140 underweight, 1,989 normal weight, 548 overweight and 145 obese women. No differences were detected in blastocyst quality among the different BMI groups, and only an initially slower embryo development was seen in obese women, which became normal at blastulation.…”

COVID-19 mRNA vaccines have no effect on endometrial receptivity after euploid embryo transfer

“…Only transfers of a single euploid frozen blastocyst using own oocytes were included. Ovarian stimulation, oocyte retrieval, intracytoplasmic sperm injection, embryo culture, embryo biopsy, genetic study and embryo vitrification and warming were carried out according to standard protocols, as previously described (Bellver et al, 2021;Cozzolino et al, 2021).…”