Association between serum unsaturated fatty acids levels and infertility among American women from the National Health and Nutrition Examination Survey 2013-2014

Background Some research indicates that unsaturated fatty acids (UFAs) in the diet could enhance reproductive outcomes in infertile women. However, other research holds different views, possibly due to differences in the conversion rates of UFAs from various foods and bioavailability in the body. Therefore, this research examined the link between serum UFAs and infertility issues. Methods This research included reproductive-age women participating in the 2013-2014 American National Health and Nutrition Examination Survey (NHANES). Serum levels of four UFAs, including palmitoleic acid (16:1n-7), vaccenic acid (18:1n-7), oleic acid (18:1n-9), and linoleic acid (18:2n-6) were measured through gas chromatography-mass spectrometry. Infertility data was collected by affirmative responses to targeted questionnaire items. Associations between serum UFA levels and infertility were evaluated utilizing Poisson regression models and smooth curve fitting methods. Sensitivity analysis was also conducted. Results This study included 535 women, aged between 18 and 45. Poisson regression analysis, both adjusted and unadjusted for confounders, revealed no associations between palmitoleic acid, vaccenic acid, oleic acid, or linoleic acid and female infertility (all P > 0.05). However, four UFAs all showed non-linear relationships with infertility in smooth curve fitting analysis. Sensitivity analysis confirmed the stability of the findings. Conclusion This research established non-linear associations between serum UFAs and infertility in American women. Specifically, maintaining appropriate serum levels of these UFAs may lower infertility risk. These findings offer new insights and practical dietary recommendations for improving female fertility.