A higher rate of MTHFR C677T homozygous polymorphism was found in patients with endometriosis (24.5% vs. 15.8%, p = 0.0453), with an adOR of 1.889 (95% CI 1.076–3.318, p = 0.0269) at the binomial logistic regression. Here, MTHFR is linked to endometriosis.