Dyspareunia, the term for painful vaginal sex, is quite common during and after menopause. About 20% to 30% of women experience this in perimenopause.
Estrogen helps keep the vaginal walls thick and stretchy and promotes vaginal lubrication. Falling estrogen levels due to menopause can cause the vaginal lining to become thinner and less elastic and the vaginal walls to produce less lubrication.
With less elasticity and lubrication, sex in menopause can be painful, with the vaginal pain lasting long after sex is over in some cases.