The Relation between Body Mass Index and Unintended Pregnancy in Women Using Contraceptive Pills

There are different ways for family planning. However, one of the problems in this field is unintended pregnancy in spite of using contraceptive pills. Although the number of unintended pregnancies in women using contraceptive pills is high, there have been limited investigations about the biological risk factors involved in the failure of this method. One of the probable risk factors is body weight. Considering the increasing prevalence of obesity in women, and since the studies in this field are insufficient, this study aimed to investigate the relation between body mass index and unintended pregnancy in women using contraceptive pills. Methods and Materials: This retrospective, descriptive, analytical study was performed on 202 fertile women with the mean age of 30 years. We used cluster random sampling to select 20 centers from therapeutic health centers in Lenjan (Iran). The data including intended or unintended pregnancy, mother and father's age and education level, number of pregnancies, age difference between children, duration of contraceptive pills consumption, and body mass index was extracted by interviewing or reading patient records. The obtained data was then analyzed using the logistic regression analysis in SPSS. Among our studied population, 82.1% had intended and 17.9% had unintended pregnancy. According to body mass index evaluation before pregnancy, 1.1% of the subjects were thin, 39.56% were normal, 47.8% were overweight, and 11.5% were obese. The duration of using contraceptive pills was less than 12 months in 39.4% and more than 49 months in 18.5% of women. According to the results, body mass index before and during pregnancy was significantly higher in women with unintended pregnancy (P = 0.004 and P = 0.008, respectively). Based on the results of this study, we can conclude that it is necessary to recommend obese women other contraceptive methods or higher doses of contraceptive pills.