A new study analyzing U.S. health data suggests that women with higher levels of body fat and waist size face a greater risk of infertility. The findings are based on data from the National Health and Nutrition Examination Survey (NHANES) collected between 2013 and 2018.
Researchers examined records from 2,875 women aged 20 to 45. They looked at a range of body measurements related to obesity, including body mass index (BMI), waist circumference (WC), and newer metrics such as body roundness index (BRI), relative fat mass (RFM), and waist-to-height ratio (WHtR).
Women were divided into five groups based on these measurements. Those in the highest group for indicators such as ABSI (a body shape index), BRI, WHtR, RFM, and BMI were found to have significantly higher odds of infertility compared to those in the lowest group.
For instance, women with the highest waist circumference had more than twice the risk of infertility than those with the lowest. The adjusted odds ratios for these indicators ranged from 1.65 to 2.28, meaning a 65% to 128% higher chance of infertility, depending on the measurement.
The study used statistical models to check for trends and patterns. Most of the indicators showed a clear linear link with infertility, meaning the risk increased steadily as the measurement went up. However, one indicator—non-HDL cholesterol to HDL cholesterol ratio (NHHR)—showed a more complex, non-linear relationship.
Notably, the researchers found that some measurements were better than BMI at predicting infertility, especially in women between 20 and 35 years old. The waist-to-height ratio, relative fat mass, waist circumference, and body roundness index all showed stronger diagnostic ability than BMI in this younger group.
The findings suggest that focusing solely on BMI may not give a complete picture of a woman’s fertility risk. According to the researchers, newer measures like WHtR, RFM, WC, and BRI could help doctors more accurately assess infertility risks in clinical settings.
Still, the study authors stress that more research is needed to confirm the results. They recommend further studies, such as long-term cohort research or genetic-based methods like Mendelian randomization, to better understand how body composition affects female fertility.
This study highlights how body shape and fat distribution—beyond just overall weight—play a role in reproductive health. As infertility becomes a growing concern for many, especially young women, these findings could shape future screening and prevention efforts.
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