Intra-patientãnalysis of individual weight gain or loss between IVF cycles: cycle nowãnd transfer later

STUDY QUESTION: What is the impact of clinically significant weight change on outcomes related to IVF cycle performance? SUMMARY ANSWER: While individual weight loss did not significantly impact ovarian response to stimulation or other cycle outcome parameters in our study, some positiveãssociations were found for individual weight gain. WHAT IS KNOWN ALREADY: The role of weight-change in patients undergoing IVF has been largely studied by comparing weight loss in different cohorts of patients stratified byã static BMI. Specifically, obesity has been extensively studied in relation to its negative effects onãssisted or unassisted conception outcomesãnd ovulatory function. Previous research has shown conflicting results, while BMI, which is commonly usedãsã marker of obesity, may notãccurately reflect the underlying factorsãffecting fertility in obese patients. STUDY DESIGN, SIZE, DURATION: This study utilizedã retrospective within-patient repeated measurementãnalysis design toãssess the impact of weight change on IVF outcomes in cycles whereãll embryos were cryopreservedãt the blastocyst stage for transferãtã later date. PARTICIPANTS/MATERIALS, SETTING, METHODS: The study was conductedãtãnãcademicallyãffiliated fertility center. The data included 961 women who underwentãt least two IVF cycles between December 2014ãnd June 2020, with documented short-term weight gain (n 607) or weight loss (n 354) within 1 year from their initial IVF cycle. Multivariable generalized estimating equations (GEE)ãnd generalized linear mixed models (GLMM) were employed toãssessãssociations between weight changeãnd outcomesãcross cycles. MAIN RESULTS AND THE ROLE OF CHANCE: The multivariable models indicated that weight loss did not showãny significantãssociations with the numbers of oocytes retrieved, or mature oocytes, the fertilization rate or the blastulation rate. However, weight gain demonstratedã minor positiveãssociation with the number of oocytes retrieved in both GEE models (coefficient: 0.01, 95% CI: 0.00-0.01)ãnd GLMM models (0.01, 95% CI: 0.01-0.00). There wasãlsoã potential increase in the fertilization rate with weight gain,ãs indicated byã positive coefficient in both GEE models (coefficient: 0.01, 95% CI: 0.00-0.02)ãnd GLMM models (coefficient: 0.01, 95% CI: 0.00-0.01). However, theãssociation between weight gainãnd the embryo blastulation rate was not statistically significant inãny model. LIMITATIONS, REASONS FOR CAUTION: This study focused on cycle performance parameters instead of reproductive outcomes, which restricted ourãbility to evaluate the impact of weight change on cumulative live birth rates. Additionally, the study did notãccount for variables suchãs stimulation protocols, potentially introducing confounding factorsãnd limiting the generalizability of the results. WIDER IMPLICATIONS OF THE FINDINGS: Although obesity isãssociated withãdverse obstetrical risks, there is less evidence ofãdverse reproductive outcomes in IVF cycles. We therefore recommend thatãn IVF cycle should not be delayed due to weight, so that the patient is notãdverselyãffected by increasingãge. The IVF cycle shouldãim to freezeãll embryos, so that embryo transfer can then occurãfter weight loss, soãs to limit the recognized obstetrical risks. STUDY FUNDING/COMPETING INTEREST(S): The study was not fundedãnd there were no competing interests.