Early or late menarche is associated with reduced fecundability in the Norwegian Mother, Father and Child Cohort Study.

Study Question: Is age at menarche associated with fecundability?

Summary Answer: Both early (<11 years) and late (>15 years) menarche is associated with decreased fecundability.

What Is Known Already: Previous studies on age at menarche and fecundability have been inconclusive. Women with early or late menarche are at increased risks of gynaecological and autoimmune diseases that may affect their ability to conceive.