Assessment of Nutritional Status and Its Influence on Ovarian Reserve: A Systematic Review

{"Background": "There is growing interest in the relationship between lifestyle factors and reproductive health. Delayed childbearing is increasing, with the average age of Spanish mothers reaching 33.05 years in 2021, above the European average of 29.5 years. Infertility affects 15\u201320% of couples of reproductive age in developed countries, and in Spain, one in six couples face fertility issues. Ovarian reserve\u2014the number and quality of oocytes\u2014is a key determinant of reproductive potential and a strong predictor of assisted reproductive technology (ART) success. While chronological age is the main determinant of ovarian reserve, emerging evidence suggests that nutritional status may also play a role. Obesity, defined as the pandemic of the 21st century, affects 46.1% of women in Spain (overweight or obese). Obesity is linked to reproductive disorders through mechanisms involving hypothalamic-pituitary-ovarian axis disruption, hyperandrogenism, insulin resistance, and chronic low-grade inflammation. This systematic review aimed to assess the influence of nutritional status on ovarian reserve in women of reproductive age.", "Methods": "A systematic literature review was conducted following the PRISMA framework. Electronic searches were performed in Medline, ScienceDirect, and the Cochrane Library, supplemented by hand-searching reference lists. The search used MeSH terms including 'ovarian reserve', 'anti-M\u00fcllerian hormone', 'nutritional status', and 'body mass index' combined with Boolean operators. Inclusion criteria were: open-access articles with abstract and full text, written in English or Spanish, published between 2011 and 2021, and including women aged 18\u201346 years. Exclusion criteria included protocols, review articles, conference proceedings, studies involving women undergoing ART procedures, and studies of women with serious diseases diminishing ovarian reserve. Study quality was assessed using the Cochrane Collaboration Risk of Bias tool, the AXIS tool for cross-sectional studies, the Newcastle-Ottawa Scale for cohort and case-control studies, and the PEDro tool for randomized clinical trials. Two authors independently reviewed articles, with discrepancies resolved by a third author. Interrater reliability yielded a Cohen's \u03ba of 0.8.", "Key Results": "The search yielded 103 articles; after removing duplicates and applying exclusion criteria, 20 studies involving 5,929 women were included. Six articles were from the USA, two from France, two from China, and one each from Taiwan, Australia, Scotland, Turkey, the United Arab Emirates, Israel, India, Brazil, Denmark, and the Philippines. The mean participant age was 32.3 years. Study designs included 8 cross-sectional, 7 cohort, 4 case-control, and 1 randomized clinical trial. BMI was used to assess nutritional status in all studies. AMH was used exclusively in 7 studies; 6 studies used AMH combined with FSH and LH; 11 studies used serum markers plus AFC by transvaginal ultrasound. In 12 of the 22 articles (54.5%), a relationship between nutritional status and ovarian reserve was demonstrated. In 7 publications (31.8%), increased BMI led to decreased ovarian reserve; 2 of these (0.9%) were in patients with PCOS, showing a decrease only if BMI > 25. In 2 articles (0.9%), there was a negative relationship between ovarian reserve and waist-to-hip ratio. In 1 article (0.45%), a positive relationship was shown between ovarian reserve and testosterone levels, the latter related to BMI. In 5 articles (22.7%), BMI was used as a confounder and was negatively related to ovarian reserve. In 4 articles (18%), no correlation was found. Two studies of women with PCOS reported that those with BMI > 25 had lower AMH levels than those with normal BMI. One study found that AMH was positively correlated with HDL cholesterol and SHBG and negatively correlated with glucose, insulin, blood glucose, BMI, and blood pressure in women with PCOS and metabolic syndrome.", "Clinical Implications": "This systematic review confirms that nutritional status, particularly high BMI, negatively impacts ovarian reserve as measured by AMH and AFC. Overweight and obese women had significantly lower AMH levels and AFC compared to normal-weight women. The findings are consistent with prior large-scale studies, including Vitek et al.'s study of 29,895 women which found lower AMH levels in obese vs. normal-weight women (1.8 \u00b1 2.0 vs. 2.1 \u00b1 2.0, p < 0.001) and lower oocyte yield (11.9 \u00b1 7.3 vs. 12.8 \u00b1 7.7, p < 0.001). Chronic inflammation from obesity induces ovarian oxidative stress affecting folliculogenesis, and lipotoxicity from persistent cytokine release has been detected in follicular fluid. Metabolic syndrome\u2014central obesity, elevated blood pressure, elevated triglycerides, elevated fasting glucose, and reduced HDL-cholesterol\u2014appears to play an important role in female fertility, potentially affecting both oocyte and embryo quality as well as endometrial receptivity. While ART may improve pregnancy chances in obese women, there is an increased risk of spontaneous abortion and implantation failure. These risks could be reduced by using oocytes from lean donors. The review's limitations include restriction to English and Spanish publications, searching only three databases, and exclusion of women undergoing ART. Nevertheless, this is one of the few systematic reviews evaluating nutritional status's influence on ovarian reserve in reproductive-age women. Future studies are needed to identify which dietary factors most affect ovarian reserve and to design prevention and health promotion strategies to improve nutritional status and reproductive health."}