Purpose: This study aimed to investigate the effects of body mass index (BMI) on infertility in women of childbearing age.
Patients and Methods: We performed a cross-sectional study using data from 3624 participants from the National Health and Nutrition Examination Survey (NHANES). We used BMI and fertility status in the survey as independent and dependent variables, respectively. We evaluated their relationship and used smoothed curve fitting and multivariate logistic regression analysis as well as a generalized additive model (GAM) to determine the effect of BMI.
Results: Logistic regression model analysis linked BMI and infertility after adjusting for potential confounders OR 1.03, 95%Cl: 1.02– 1.05). There was a non-linear relationship between BMI and infertility, with each unit increase in BMI reducing the risk of infertility by 33% when BMI was < 19.5 kg/m². In contrast, when BMI ≥ 19.5 kg/m², each unit increase in BMI predicted a 3% increase in the risk of infertility.
Conclusion: The relationship between infertility and BMI presented a U-shaped curve. Therefore, a BMI that lay at the extremes of the spectrum tended to predict infertility. We believe that this study will support the maintenance of suitable BMI levels in women preparing for pregnancy.
Keywords: BMI, infertility, nonlinear, NHANES