Relaxin is a peptide hormone whose presence rises significantly during pregnancy. It facilitates physical changes necessary for a growing fetus and eventual childbirth. Understanding how long this hormone remains in the body after delivery is a common concern for new parents navigating physical recovery. This article details relaxin’s function and provides a timeline for its clearance from the bloodstream following birth.
Functions of Relaxin
The hormone relaxin is produced mainly by the corpus luteum in the ovary, and later by the placenta and the lining of the uterus during pregnancy. Its main role is to soften and loosen various tissues and ligaments in the body. Relaxin prepares the body for labor by remodeling connective tissue.
Relaxin increases the laxity of ligaments and joints, particularly those in the pelvis. This flexibility is necessary to accommodate the growing fetus and facilitate the baby’s passage through the birth canal. Beyond the musculoskeletal system, relaxin also helps soften and thin the cervix as labor approaches. It also inhibits uterine contractions in the early stages and regulates the mother’s cardiovascular system to manage increased blood volume.
Timeline for Relaxin Clearance After Delivery
The concentration of relaxin in the bloodstream declines rapidly once the placenta is delivered, as it is a major source of the hormone. Despite this immediate drop, measurable levels remain in the body for a considerable time postpartum. Studies indicate that the majority of relaxin is metabolized and cleared by the liver within the first 12 weeks following childbirth.
The duration it takes for levels to return to a non-pregnant baseline varies among individuals. Residual relaxin can linger in the system for up to five to six months. For those who are breastfeeding, the hormone may persist even longer, sometimes approaching a full year.
The physical effects of relaxin lag behind its hormonal clearance from the bloodstream. Ligaments and connective tissues, softened and stretched over nine months, do not instantly regain their pre-pregnancy rigidity. The resulting joint instability and laxity, particularly in the pelvis and lower back, can therefore continue to be felt for months after the hormone has largely been cleared. This extended period of tissue recovery explains why many individuals experience joint instability long after their six-week postpartum checkup.
Managing Postpartum Physical Changes
While the body is undergoing this gradual process of hormonal clearance and tissue recovery, the residual ligament laxity requires a mindful approach to physical activity. Because joints are looser than normal, it is beneficial to focus on stability rather than flexibility in the initial postpartum period. This means avoiding movements that push joints to their maximum range of motion, such as deep stretches or overextension exercises.
Recovery should focus on rebuilding the strength of the deep core muscles and the pelvic floor, which function as natural stabilizers. Targeted exercises help create muscular support around the joints that relaxin has temporarily destabilized. Seeking guidance from a physical therapist specializing in pelvic health can ensure these exercises are performed safely and effectively.
When lifting the baby or other heavy objects, maintaining proper posture and utilizing core engagement helps protect the back and pelvic joints. Avoiding high-impact activities like running or intense jumping in the early months is recommended until core and pelvic stability are significantly restored. If persistent pain or an unstable feeling occurs, especially during single-leg activities like climbing stairs, seeking professional assessment is advisable.