Early Menarche is Associated with Increased Risk of Endometriosis
Early menarche (before age 12) is associated with an increased risk of endometriosis, making option C the correct answer. 1, 2, 3, 4, 5
Evidence Supporting Early Menarche as a Risk Factor
The relationship between early menarche and endometriosis is well-established across multiple high-quality sources:
Early menarche (age <12 years) confers a 2-fold increased risk of endometriosis compared to women with menarche at age ≥15 years 1
A 2023 meta-analysis demonstrated that early menarche is associated with a pooled odds ratio of 1.34 (95% CI 1.16-1.54) for endometriosis, with this risk increasing in more recent studies started after 2000 (OR 1.62) compared to older studies 2
The 2025 JAMA review confirms that younger age at menarche is a recognized risk factor for endometriosis 4
A systematic review and meta-analysis found a small but significant increased risk, with women with endometriosis having a 55% probability of earlier menarche than controls 5
Why Other Options Are Incorrect
Late menarche (Option A) is actually protective: Menarche after age 14 years is strongly and inversely associated with endometriosis (OR 0.3; 95% CI 0.1-0.6), representing a 70% risk reduction 6
Long menstrual cycle (Option B) is not associated: While shorter menstrual cycle length shows a suggestive trend toward increased risk, longer cycles are not established risk factors 3, 6
Late menopause (Option D) is not a primary risk factor: The evidence focuses on early reproductive characteristics rather than late menopause as endometriosis risk factors 1
Clinical Mechanism
The increased risk with early menarche likely relates to prolonged lifetime exposure to ovulatory menstrual cycles and estrogen, as endometriosis is an estrogen-dependent inflammatory disease 4. Earlier onset of menstruation means more cumulative exposure to the hormonal environment that promotes endometrial-like tissue growth outside the uterus 3.
Additional Context
Other established risk factors that commonly co-occur include shorter menstrual cycle length, lower body mass index, nulliparity, and early history of dysmenorrhea 3, 4, 6. The diagnostic delay for endometriosis averages 5-12 years after symptom onset, making recognition of these early risk factors clinically important 4.