Background: Infertility considered a traumatic life event and assisted reproductive technology is a revolution for infertility treatment, in vitro fertilization is one of the most common assisted reproductive technology procedures performed, there are so many factors that affect the success rate of in vitro fertilization. Body mass index is one of the controlled factors which affecting in vitro fertilization success. Aim The aim of this study was to explore the relation between maternal body mass index & in vitro fertilization success rate. Subject and methods: a descriptive correlational design conducted by prospectively investigating the in vitro fertilization cycles of 100 women they were within the age from 25 to 35 years who were selected based on the inclusion and exclusion criteria in a private assisted reproductive technology clinic between 2015 and 2016. The women were classified into six groups based on their body mass index, i.e., under weight (n=5), normal weight (n=9), overweight (n=36), obese grade I (n=32), obese grade II (n=14), and obese grade III (n=4). Then, body mass index - and related variations in the in vitro fertilization cycle parameters and clinical pregnancy rates of women were investigated. T-test and analysis of variance One Way ANOVA test were used. For finding the differences between categorical data, nonparametric Chi-square (X2) test was used to determine whether there was a relation between body mass index and in vitro fertilization success rate. Results: Finding of the study show that the mean age is 29.75± 3.88 years. According to the classes of body mass index, 36% of women were overweight body mass index (25-29.9kg/m), 32% were grade I obesity body mass index (30-34.9kg/m), 9% normal weight body mass index (18.5-24.9kg/m), and 5% underweight body mass index ( less than18.9kg/m). Eighty-one percent of women had primary infertility. Variations in variables with body mass index showed that doses of drugs for ovulation induction were negatively affected by body mass index. Ovulation induction cycles were found to be negatively affected by body mass index. Chemical pregnancy rate was found to be negatively affected by body mass index. Higher implantation rate was associated with normal body weight .Clinical pregnancy rates were found to be lower in the obesity grade III than in the other groups. Conclusion: The present study evaluated the relation between body mass index and in vitro fertilization success rates according to their body mass index groups, the clinical pregnancy rates were observed to be lower in the obesity grade III than in the other body mass index groups. Recommendations: Provide women undergoing in vitro fertilization process with a counseling program or teaching class about factors affecting the success of the procedure, administration of medication and follow up. Keywords:Body mass index, success rate, in vitro fertilization
