Implications of blood type for ovarian reserve

Background We explored the relevance of blood type to ovarian reserve, as reflected by early follicular phase FSH levels. Methods For this cross-sectional observational study, early follicular phase serum levels of FSH (mIU/ml) and estradiol (E2, pg/ml), and information on blood type (A, B, AB and O) and patient age were procured for female patients, ≤45 years age (n = 544), who were undergoing fertility evaluation at one of two tertiary care facilities. Serum FSH > 10 mIU/ml was taken to reflect diminished ovarian reserve (DOR). Data distribution for FSH and age was analyzed and non-parametric tests used for comparisons across blood groups. Multivariable logistic regression analyses determined the relationship between elevated FSH and respective blood types after adjusting for age and study site. Results Prevalence of blood types according to order of frequency was: O (45), A (35), B (16) and AB (5). After adjusting for age and study site, patients with blood type O were twice as likely to exhibit FSH > 10 mIU/ml compared with those with A or AB blood types [odds ratio (OR) 2.36; 95 confidence interval (CI) 1.274.41; P = 0.007], and three times as likely to manifest FSH > 12m IU/ml (OR 3.48, 95 CI 1.467.32, P = 0.004). The B blood group antigen failed to exhibit any relationship with ovarian reserve as reflected by baseline FSH (P> 0.05). Conclusions The A blood group antigen appears to be protective for ovarian reserve, whereas blood type O appears to be associated with DOR, in a relationship that is independent of advancing age. Further studies are needed to establish causality and identify the underlying mechanisms for the association.