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Background: Although observational studies have demonstrated that blood lipids are associated with female infertility, the causality of this association remains unclear. We performed a univariable and multivariable Mendelian randomization (MR) analysis to evaluate the causal relationship between blood lipids and female infertility. Methods: Single-nucleotide polymorphisms associated with lipid traits in univariate analysis were obtained from the Million Veteran Program (MVP) and Global Lipids Genetics Consortium (GLGC), involving up to 215,551 and 188,577 European individuals, respectively. Blood lipids in multivariate analysis were obtained from the latest genome-wide association study meta-analysis with lipid levels in 73 studies encompassing >300,000 participants. Data on female infertility were obtained from the FinnGen Consortium R6 release, which included 6481 samples and 75,450 controls. Subsequently, MR analysis was performed using inverse variance-weighted (IVW), weighted median, weighted-mode, simple-mode and MR-Egger regression to demonstrate the causal relationship between lipids and female infertility. Results: After controlling confounding factors including body mass index and age at menarche, two-sample MR demonstrated that genetically predicted LDL-C and TC were causally associated with the risk of female infertility (When the genetic instruments come from the MVP database, LDL-C and female infertility, IVW OR: 1.13, 95% CI: 1.001–1.269, p = 0.047; TC and female infertility, IVW OR: 1.16, 95% CI: 1.018–1.317, p = 0.025, and when the genetic instruments came from the GLGC database, LDL-C and female infertility, IVW OR: 1.10, 95% CI: 1.008–1.210, p = 0.033; TC and female infertility, IVW OR: 1.14, 95% CI: 1.024–1.258, p = 0.015). However, the IVW estimate showed that HDL-C was not significantly associated with the risk of female infertility (when the genetic instruments came from the MVP database, IVW OR: 1.00, 95% CI: 0.887–1.128, p = 0.999; when the genetic instruments came from the GLGC database, IVW OR: 1.00, 95% CI: 0.896–1.111, p = 0.968). The multivariable MR analysis also provided evidence that LDL-C (OR: 1.12, 95% CI: 1.006–1.243, p = 0.042) was significantly associated with the risk of female infertility after considering the correlation of all lipid-related traits. Conclusion: These findings support a causal relationship between increased LDL-cholesterol and increased female infertility risk. Furthermore, the association between lipid-related traits and female infertility risk merits more studies. [ABSTRACT FROM AUTHOR]

Excessive uric acid levels may affect several organs and systems in the body. There is limited evidence of the effects of high serum uric acid levels on the female reproductive system. This study used the National Health and Nutrition Examination Survey (NHANES) database to explore the relationship between serum uric acid and female infertility. This cross-sectional study included a total of 2197 eligible subjects using data from NHANES 2013-March 2020 pre-pandemic data. Self-reported infertility (ever experiencing an inability to conceive after 12 months of trying to become pregnant) was the main outcome. Logistic regression models and restricted cubic spline were used to analyze the relationship between serum uric acid and female infertility, and stratified analysis was carried out. A total of 295 women self-reported infertility (13.43%). The median uric acid level for all study subjects was 4.4 mg/dL (interquartile range [IQR]: 3.7, 5.1). Serum uric acid levels were higher in the infertility group than in the control group (4.7 mg/dL [IQR: 4.0, 5.3] vs. 4.4 mg/dL [IQR: 3.7, 5.1], P < 0.001). After adjusting for age, race, marital status, smoking, alcohol, history of pregnancy, history of diabetes, history of hypertension, fasting glucose, total cholesterol, creatinine in refrigerated serum, low-density lipoprotein cholesterol, direct high-density lipoprotein cholesterol, glycohemoglobin, and body mass index confounders, women with serum uric acid levels at Q3 (4.4–5.1 mg/dL) had a 73% (odds ratio [OR] = 1.73, 95% confidence interval [CI] 1.18, 2.54, P = 0.005) higher risk of infertility, and women with uric acid levels at Q4 (5.1–18.0 mg/dL) had an 83% (OR = 1.83, 95% CI 1.22, 2.75, P = 0.003) increased risk of infertility compared to women at Q1 (1.6–3.7 mg/dL). The restricted cubic spline also showed that when serum uric acid levels exceeded the reference value, the risk of infertility gradually increased. We also performed a sensitivity analysis based on the complete dataset and found that the results were robust. Higher serum uric acid levels were significantly associated with an increased risk of female infertility. Women planning a pregnancy should have increased serum uric acid monitoring. [ABSTRACT FROM AUTHOR]