Distribution of ABO and Rh Blood Groups in Patients With Endometriosis at King Abdulaziz University Hospital: A Case-Control Study.

Background There is no sound evidence for the association of blood groups with the risk of endometriosis, and no studies from Saudi Arabia have examined this association. Therefore, the primary aim was to determine whether there is an association between the distribution of ABO and Rh blood groups and the incidence of endometriosis in a cohort from Saudi Arabia and also to evaluate the potential risk factors related to endometriosis among the population.  Methods This case-control study included women diagnosed with endometriosis (n = 44) who presented to King Abdulaziz University Hospital Obstetrics and Gynecology Clinic, Jeddah, Saudi Arabia, between 2010 and 2021. Women from the blood donors database of King Abdulaziz University Hospital were included as a control group (n = 184). The total sample size was 228. Demographic data, diagnosis method, ABO blood type, and Rh blood type were obtained from hospital records. In addition, data were collected from self-reported questionnaires, which included family history, dysmenorrhea, age of menarche, age of childbearing, number of children, history of abortion, parity, number of children, use of oral contraceptives for alleviating dysmenorrhea, iron deficiency, duration of menstrual flow, and volume of bleeding during menses. Odds ratio, Pearson chi-squared test (χ2), and independent t-test were used to analyze the associations between variables. Results Most of the participants had blood type O (n = 117, 51.3%), which was followed by blood type A (n = 59, 26.0%), and the majority were Rh+ (n = 215, 94.3%). There was no significant difference in the risk of endometriosis according to ABO (P = 0.237) and Rh (P = 0.283) blood types. However, endometriosis was found to have a significant relationship with dysmenorrhea, heavy bleeding during menses, history of abortion, long duration of menstrual flow, lower number of children, late pregnancy, and use of oral contraceptive pills to relieve dysmenorrhea (p ≤ 0.05). Conclusions The present results indicate that ABO and Rh blood types are not associated with the risk of endometriosis. However, there was a strong, significant association between endometriosis and other factors.