How does relaxin help during childbirth?

During childbirth, the hormone relaxin plays a vital role in preparing the body for parturition. Produced primarily by the corpus luteum, placenta, and uterus, it facilitates the delivery process through two primary mechanisms:1

• Pelvic Relaxation: Relaxin induces the loosening of the joints between the pelvic bones, specifically the pubic bones and the sacrum. This increased elasticity helps the body accommodate the physical strain of pregnancy and eases the passage of the fetus through the birth canal.12
• Cervical Ripening: The hormone promotes the softening, or ripening, of the cervix by stimulating collagen remodeling. This process ensures the cervix is sufficiently flexible to allow for a smooth delivery.1

While these effects are essential for birth, excessive relaxation of the pelvic joints can sometimes lead to discomfort, such as backaches or difficulty walking, for the mother.2