Impact Of Body Mass Index On Embryo Development And ART Outcomes In Childbearing Males And Females

【Background】With social development and lifestyle changes,obesity has become a significant public health issue.In China,about 600 million people are overweight or obese,and a high body mass index（BMI）seriously endangers the health of the population,affecting the reproductive function of men and women of childbearing age.Currently,there is a considerable amount of research focused on the impact of obesity on assisted reproductive technology（ART）outcomes.However,due to differences in population characteristics,ovulation protocols,and transfer options,the impact of obesity on fertility outcomes remains controversial.In addition,most studies have not explored the process of embryo development,and there is limited data on low-weight and male patients,so further research is needed to confirm the impact of body mass index.【Objective】This study aims to investigate the effect of male and female BMI on embryo development and ART outcomess,providing better ART treatment for patients with different BMI,improving ART outcomes and obtain a healthy fetus【Methods】This study conducted from January 2015 to October 2021 at the Reproductive Medicine Center of the First Affiliated Hospital of Hainan Medical University,which retrospectively collected data of patients who received ART treatment.The patients were divided into four groups based on their BMI:low weight group（BMI<18.5kg/m²）,normal weight group（18.5≤BMI<24 kg/m²）,overweight group（24≤BMI<28 kg/m²）,and obese group（BMI≥28 kg/m²）.This study consisted of two parts.The first part studied the effect of female BMI on embryo development and ART outcome,including 3783 female patients who underwent their first ART with fresh embryo transfer and ovulation by long protocol,comparing the differences in basic information,ART process,embryo development and ART outcomes among the four groups.In the second part,we investigated the effect of male BMI on embryo development and pregnancy outcomes,including 1946 male patients who underwent in vitro fertilization（IVF）and whose spouses received fresh embryo transfer for the first time,comparing the differences of semen quality,embryo development and pregnancy outcomes among the four groups.All patients’spouses had a normal BMI.【Results】The first part investigated the effect of female body mass index on embryo development and ART outcome:Firstly,the basic characteristics of female patients were analyzed and it was found that the duration of infertility was significantly prolonged in the obese group（P=0.007）.Basal Follicle-stimulating hormone（FSH）,basal Luteinizing hormone（LH）,basal Estradiol（E₂）,basal Progesterone（P）,and anti-Mullerian hormone（AMH）in the obese group were lower than those in the normal weight group（P<0.05）,and the number of antral follicle counting（AFC）was reduced in the obese group（P=0.011）.The overweight group only showed a decrease in E₂and P levels（P<0.05）.During the ART,there was a significant difference in Gonadotropin（Gn）dosage among the four groups,with the obese group using the most,followed by the overweight group,and the low weight group using the least（P<0.001）.The number of days of Gn use was prolonged in the obese group（P<0.001）.LH,E2,and P on trigger day were all lower in the overweight and obese groups than in the normal weight group（P<0.05）.Comparison of embryo development revealed that the obese group showed developmental delay at the Time of pronuclei disappearance（t PNf）,Time of four cells（t4）,and Time of full blastocyst formation（t B）compared to the normal weight group（P<0.05）.The ART outcomes were worse in the obese group,as evidenced by a decrease in clinical pregnancy rate（P=0.044）and live birth rate（P=0.036）.After logistic regression,obesity was found to be a risk factor for clinical pregnancy（OR=0.683,95%CI:0.479-0.973,P=0.035）and live birth（OR=0.662,95%CI:0.459-0.954,P=0.027）.Female age was a risk factor for biochemical pregnancy,clinical pregnancy and live birth（P<0.05）.The second part of the study investigated the impact of male BMI on embryo development and ART outcome.Comparing the sperm quality of male patients,it was found that the total sperm count（P=0.049）and normal morphology rate（P=0.025）of the low weight group were lower than those of the normal group.Embryo dynamics data revealed that blastocysts in the obese group showed a delay about 0.9 hours at the three cells stage（P=0.036）.Although the biochemical pregnancy rate,clinical pregnancy rate,and live birth rate of the low weight group were the lowest among the four groups,the differences were not statistically significant（P>0.05）.Logistic regression revealed that low weight was a risk factor for live birth（OR=0.590,95%CI:0.359-0.970,P=0.037）.Male age was a risk factor for biochemical pregnancy,clinical pregnancy and live birth（P<0.05）.【Conclusions】Female obesity prolongs the duration of infertility,causes endocrine disorders,reduces the antral follicle counting,increase the dosage and duration of Gn,and leads to poorer ART outcomes.Low body weight in men has a negative impact on total sperm count and normal morphology rate,resulting in poorer IVF outcomes for their spouse.Both male and female obesity can delay the blastocyst development process.Obesity in women is a risk factor for clinical pregnancy and live birth,while low body weight in men is a risk factor for live birth.