How can a large penis cause problems for women during sex?

When it comes to penises, bigger isn't always better. It may be impressive on film -- the late porn star John Holmes allegedly boasted a 13.5-inch-long penis -- but reality is a different story. The average vagina is about 3 inches deep and only about 4 inches deep when completely aroused, while the average penis is about 5 to 6 inches in length and about 5 inches in circumference. You don't have to be a mathematician to figure out that anything too much bigger than that is going to be, well, a tight squeeze.

Although the vagina has an incredible ability to stretch (think childbirth!), a penis that's larger than average can be uncomfortable for some women during vaginal and anal sex, and may trigger a gag reflex during oral sex. Long penises may hit your cervix during thrusting, which can be painful. And a penis with extra girth may tear delicate vaginal tissues if you don't use enough lubricant and can trigger urinary tract infections if it rubs and irritates your urethra.

A large penis will usually only cause problems during sex if something important is missing, says obstetrics and gynecology specialist Dr. Lauren Streicher. Learn more by watching this video.