During pregnancy, which hormones are MOST likely responsible for ligamentous laxity at the pubic symphysis?

• A. Relaxin and Progesterone
• B. Relaxin and Estrogen
• C. Progesterone and Estrogen
• D. Estrogen and Prolactin

Answer: (A)

During pregnancy, hormonal changes loosen pelvic ligaments to prepare for childbirth. The hormone most directly linked to this pelvic laxity is relaxin. Relaxin acts on connective tissue to soften and increase the elasticity of ligaments, particularly those in the pelvis such as the pubic symphysis, so they can stretch as the pelvis widens for delivery.

Progesterone also rises during pregnancy and contributes to tissue relaxation around the pelvis. This team of relaxant effects helps explain why the pubic symphysis and other pelvic joints become more mobile as pregnancy progresses.

Estrogen can influence ligament laxity as well, but the combination in this option—relaxin with progesterone—is the one most commonly highlighted for pelvic joint looseness in pregnancy in exam contexts. Clinically, this increased laxity can lead to symptoms like pelvic girdle pain or mild diastasis at the pubic symphysis, which is why management often includes activity modification and supportive strategies.