Relaxin and Hypermobility in Pregnancy: Risks and Care

During the gestational period, the female body undergoes a series of profound and complex physiological, hormonal, and biomechanical changes, necessary to accommodate fetal development and prepare the body for childbirth. Among the main culprits for these structural changes is a specific peptide hormone, whose action is fundamental but, at the same time, potentially problematic for the stability of the musculoskeletal system. The action of relaxin pregnancy joints represents a crucial factor in the development of alterations affecting the musculoskeletal system, inducing a state of generalized ligamentous laxity. This phenomenon, although physiologically indispensable to allow the expansion of the pelvis, can result in a condition of joint hypermobility, exposing the pregnant woman to a greater risk of developing painful dysfunctions, biomechanical overloads, and postural alterations. Understanding the mechanisms through which this hormone acts on connective tissues is essential for setting up adequate prevention and clinical management strategies. It is therefore imperative that every assessment and treatment pathway be supervised by qualified healthcare personnel; it is always recommended to consult your doctor or physical therapist for a personalized and safe evaluation.

Table of Contents

• Physiology and Mechanism of Action: The Role of relaxin pregnancy joints
• Biomechanics Impact of relaxin pregnancy joints on the Female Body
• Occupational Risks and INAIL Data on Gestational Hypermobility
• Clinical and Physiotherapeutic Assessment of Gestational Hypermobility
• Prevention and Physiotherapeutic Management Strategies
• Ergonomics and Daily Postural Hygiene
• Postpartum Recovery and Tissue Normalization
• FAQ: Frequently Asked Questions about Hypermobility in Pregnancy
• Frequently Asked Questions
• Sources and Scientific References

Physiology and Mechanism of Action: The Role of relaxin pregnancy joints

Relaxin is a peptide hormone belonging to the insulin superfamily, secreted mainly by the ovarian corpus luteum, decidua, and placenta during gestation. Serum levels of this hormone undergo a rapid increase starting from the first weeks of pregnancy, reaching a peak towards the end of the first trimester, then stabilizing and showing a new, albeit slight, increase near childbirth (MacLennan et al., 1986). The primary biological objective of relaxin pregnancy joints is to remodel connective tissue, reducing cervical rigidity and increasing the elasticity of pelvic ligaments, particularly those stabilizing the pubic symphysis and sacroiliac joints.

At a biochemical level, relaxin exerts its function by binding to specific receptors (RXFP1 and RXFP2) present in fibroblasts and connective tissue cells. The activation of these receptors triggers a cascade of intracellular signals that leads to an upregulation of matrix metalloproteinases (MMPs), enzymes responsible for the degradation of collagen and other extracellular matrix proteins. Simultaneously, an inhibition of tissue inhibitors of metalloproteinases (TIMPs) is observed, favoring a net balance towards collagen catabolism (Dehghan et al., 2014). This process alters the structural composition of the ligaments, decreasing the density of type I collagen fibers, responsible for tensile strength, and increasing the proportion of type III collagen, which is more elastic but less resistant. The clinical result is a marked decrease in ligamentous *stiffness*, which translates into an increase in joint range of motion (ROM), known as gestational hypermobility or joint laxity.

Although the hormone’s action is primarily aimed at the pelvic girdle, its effects are systemic. Relaxin receptors are distributed throughout the musculoskeletal system, which explains why ligamentous laxity also involves the spine, upper and lower limb joints, and even the small joints of the hands and feet. This systemic hypermobility, combined with the progressive increase in body weight and the anterior shift of the center of gravity, creates a highly vulnerable biomechanical environment, requiring accurate preventive intervention from the doctor or physical therapist.

Biomechanics Impact of relaxin pregnancy joints on the Female Body

The interaction between increased body mass, volumetric changes in the abdomen, and laxity induced by relaxin pregnancy joints generates a profound reorganization of female biomechanics. The neuromuscular system is forced to compensate for the loss of passive stability (provided by ligaments) by increasing active work (provided by muscles), which frequently leads to states of early fatigue, muscle spasms, and painful syndromes.

Alterations of the Pelvic Girdle and Pubic Symphysis

The pelvic girdle is the area most affected by hormonal changes. The pubic symphysis, a fibrocartilaginous joint that unites the two pubic bones anteriorly, undergoes a physiological widening from the normal 2-3 millimeters up to 7-9 millimeters during the third trimester. When this widening exceeds physiological limits or is accompanied by asymmetric instability of the posterior sacroiliac joints, a clinical picture known as Pelvic Girdle Pain (PGP) develops (Vleeming et al., 2008). Patients suffering from PGP complain of acute pain, often described as stabbing, localized at the pubic symphysis, radiating towards the groin, the medial aspect of the thighs, or posteriorly towards the buttocks. The pain typically exacerbates during asymmetric loading activities, such as walking, climbing stairs, dressing while standing on one leg, or turning in bed. The laxity of the sacroiliac ligaments (interosseous, anterior and posterior sacroiliac, sacrotuberous, and sacrospinous) compromises the “form closure” mechanism of the pelvis, making it essential to strengthen the “force closure” through targeted muscular intervention, which must be carefully planned by the doctor or physical therapist.

Modifications of the Spine and Posture

Uterine growth causes an anterior and superior shift of the body’s center of gravity. To maintain balance, the pregnant woman instinctively adopts a compensatory posture characterized by an accentuation of lumbar lordosis and an anterior pelvic tilt. The laxity of the anterior and posterior longitudinal ligaments, ligamenta flava, and interspinous ligaments, induced by hormonal action, reduces the spine’s ability to resist shear forces. This mechanical overload concentrates at the lumbar facet joints and the lumbosacral junction (L5-S1). Furthermore, lumbar hyperlordosis is often accompanied by an increase in thoracic kyphosis and an anterior positioning of the head and shoulders, necessary to balance the weight of the growing breasts. This complex postural alteration is the basis of gestational low back pain, a condition affecting over 50% of pregnant women (Wu et al., 2004). The paravertebral muscles, multifidus muscles, and quadratus lumborum are subjected to continuous isometric tension, resulting in painful contractures and myofascial trigger points.

Impact on Peripheral Joints and the Plantar Arch

The systemic effects of hypermobility are also evident in peripheral joints. In the lower limbs, the increase in body weight associated with laxity of the plantar ligaments (particularly the plantar fascia and the plantar calcaneonavicular or “spring ligament”) leads to a progressive collapse of the medial longitudinal arch. This phenomenon results in excessive foot pronation and acquired flatfoot, which alters the entire kinematic chain of the lower limb. Foot pronation induces internal rotation of the tibia, which in turn favors dynamic knee valgus, increasing stress on the medial compartment of the femorotibial joint and the patellofemoral joint (Segal et al., 2012). In the upper limbs, ligamentous laxity can predispose to shoulder and wrist instability. Carpal Tunnel Syndrome is a frequent occurrence, caused not only by the fluid retention typical of pregnancy but also by altered biomechanics of the carpal bones which, due to laxity, reduce the space available for the median nerve.

Occupational Risks and INAIL Data on Gestational Hypermobility

Joint hypermobility induced by hormonal changes is not only an individual clinical problem but also a significant risk factor in the workplace. Italian legislation, particularly Legislative Decree 81/08 and Legislative Decree 151/01 (Consolidated Law for the Protection of Maternity), places specific emphasis on the protection of pregnant workers, recognizing that biomechanical alterations significantly increase susceptibility to injuries and work-related musculoskeletal disorders.

The National Institute for Insurance against Accidents at Work (INAIL) has published various guidelines and technical documents relating to the assessment of biomechanical risk in pregnancy. According to INAIL data and indications, ligamentous laxity reduces tissue tolerance to mechanical loads, making tasks that would normally be considered low risk dangerous. Manual handling of loads (MHL), repetitive movements, prolonged incongruous postures, and exposure to mechanical vibrations become critical risk factors.

INAIL emphasizes that the reduction in joint stability leads to a decrease in grip strength and an alteration of proprioception, increasing the risk of sprains, dislocations, and accidental falls. Workers employed in the healthcare sector (nurses, social and healthcare workers), retail, manufacturing, and cleaning services are the categories most exposed to developing musculoskeletal disorders (MSDs) during gestation, due to the combination of physical work demands and joint vulnerability.

In light of this evidence, it is the employer’s obligation, in collaboration with the competent physician, to carry out a specific risk assessment for the pregnant worker, providing, where necessary, for the adaptation of working conditions, modification of duties, or early abstention from work. In this context, the opinion of the doctor or physical therapist is essential to certify functional limitations and suggest appropriate ergonomic modifications.

Clinical and Physiotherapeutic Assessment of Gestational Hypermobility

The clinical assessment of hypermobility and associated dysfunctions requires a rigorous methodological approach. Physiotherapeutic evaluation should not be limited to quantifying pain but must analyze in detail global biomechanical function, motor control strategies, and the impact of alterations on activities of daily living (ADL). It is fundamental that such an evaluation be conducted exclusively by the doctor or physical therapist, in order to exclude strictly medical conditions (such as severe radiculopathies, deep vein thrombosis, or obstetric complications).

The measurement of generalized hypermobility is traditionally performed using the Beighton Score, a validated scale that assesses the extension of specific joints (little finger, thumb, elbow, knee, and trunk flexion). However, in pregnancy, the use of this tool requires caution: trunk flexion is hindered by abdominal bulk, and knee extension can be altered by edema. Therefore, the evaluation focuses more on pain provocation tests and functional stability tests specific to the pelvis and spine (Mens et al., 2001).

• Active Straight Leg Raise (ASLR) Test: This is the gold standard test for assessing load transfer capacity through the pelvis. The patient, in a supine position, is asked to actively lift an extended lower limb approximately 20 centimeters from the bed. If the movement is difficult, painful, or impossible, the test is positive for a “force closure” deficit. The physical therapist can repeat the test by applying manual compression at the iliac crests: if compression facilitates movement or reduces pain, pelvic instability and the indication for using a pelvic belt are confirmed.
• Posterior Pelvic Pain Provocation (P4) Test: Used to diagnose sacroiliac joint pain. With the patient supine, the hip is flexed to 90 degrees, and the physical therapist applies axial pressure along the femur, pushing posteriorly towards the sacroiliac joint. The appearance of familiar pain in the gluteal region indicates sacroiliac dysfunction.
• Palpation of the Pubic Symphysis: Tenderness on direct palpation of the pubic symphysis and associated ligaments is a primary clinical sign of pubic dysfunction.
• Motor Control Assessment: The ability to isolate and synergistically activate the transversus abdominis muscle, pelvic floor muscles, and lumbar multifidus muscle is analyzed. These muscles constitute the central “stability cylinder” (core), and their dysfunction is closely related to lumbopelvic pain.

Prevention and Physiotherapeutic Management Strategies

The management of musculoskeletal dysfunctions resulting from hormonal action on ligaments is based on a conservative and multimodal approach. The main objective of physiotherapy is not to counteract the physiological action of the hormone, but rather to provide the body with neuromuscular and ergonomic strategies to compensate for the loss of passive stability. Any rehabilitation program must be personalized and approved by the doctor or physical therapist, taking into account the gestational age, previous fitness level, and specific clinical limitations.

Therapeutic Exercise and Stabilization (Core Stability)

Therapeutic exercise represents the cornerstone of conservative treatment (Stuge et al., 2004). Since ligaments are unable to provide adequate support, it is necessary to increase active stability through strengthening the deep musculature. The program focuses on:

1. Transversus Abdominis Activation: This muscle acts as a natural corset. Training involves sub-maximal isometric contractions (the “drawing-in” maneuver or pulling the navel towards the spine), performed in safe positions such as quadruped, side lying, or sitting.
2. Pelvic Floor Strengthening: Perineal muscles work synergistically with the transversus abdominis to stabilize the pelvis from below. Kegel exercises, performed correctly, improve continence and contribute to the “force closure” of the pelvic girdle.
3. Gluteal Muscle Strengthening: The gluteus maximus and gluteus medius are fundamental stabilizers of the sacroiliac joint and hip. Exercises such as the “clam shell” (side-lying hip abduction) or modified glute bridges are highly indicated to counteract knee valgus and pelvic instability.
4. Postural Control: Axial self-lengthening exercises and gentle spinal mobility (such as the cat-camel exercise in quadruped) help maintain muscle flexibility without stressing hypermobile ligaments.

It is imperative to avoid exercises involving high impact (jumps, running), extreme passive stretches (end-range stretching), or sudden asymmetrical movements, which could cause microtrauma to ligaments already made vulnerable by laxity.

Manual Therapy and Myofascial Release Techniques

Manual therapy, performed by specialized personnel, offers valuable support for pain management. The techniques employed must be gentle and respect the physiology of pregnancy. High-velocity, low-amplitude (HVLA) vertebral manipulations (the so-called “thrusts”) are contraindicated due to the risk of ligamentous injuries. Instead, preference is given to:

• Therapeutic Massage: Useful for reducing tension in overloaded muscles, particularly the lumbar paravertebrals, piriformis, glutes, and suboccipital muscles.
• Myofascial Release Techniques: Applied with gentle pressure to improve tissue gliding and reduce trigger points.
• Gentle Joint Mobilizations: Rhythmic movements of grades I and II to modulate pain and maintain joint lubrication, without forcing the physiological limits of the joint.

Use of Orthoses and External Supports

When therapeutic exercise is not sufficient to ensure the necessary stability for daily activities, the use of external orthopedic supports is extremely effective. The prescription of such devices must be evaluated by the doctor or physical therapist.

• Pelvic Belts: Applied at the level of the sacroiliac joints (immediately above the greater trochanters of the femur), these belts provide mechanical compression that simulates “force closure,” significantly reducing pain during walking and loading. They should be worn during at-risk activities and removed at rest.
• Orthopedic Insoles: In cases of severe collapse of the plantar arch and the onset of fasciitis or posterior tibial tendinopathy, the use of custom-made insoles with medial arch support and calcaneal unloading helps restore correct lower limb biomechanics, reducing torsional forces on the knee and pelvis.
• Graduated Compression Stockings: Although they do not directly act on hypermobility, they reduce peripheral edema, improving ankle and foot joint mobility and reducing the feeling of heaviness.

Ergonomics and Daily Postural Hygiene

Lifestyle modification and the adoption of correct ergonomic rules are essential to minimize mechanical stress on hypermobile joints. Patient education, conducted by the doctor or physical therapist, focuses on optimizing activities of daily living (ADL).

During sleep: Side lying is recommended, preferably on the left side to promote venous return. The use of support pillows is fundamental: a pillow placed between the knees and ankles maintains neutral alignment of the hips and pelvis, reducing tension on the sacroiliac joints. An additional pillow can be placed under the abdomen to support the weight of the uterus and prevent rotation of the lumbar spine.

During postural transitions: The transition from supine to sitting (and vice versa) must always occur by passing through the side-lying position (the “log roll” technique). This avoids asymmetrical activation of the rectus abdominis muscles and prevents excessive stress on the pubic symphysis and the worsening of any diastasis recti.

In standing and walking: It is necessary to distribute weight equally on both lower limbs, avoiding the asymmetrical posture with weight on only one leg (typical resting posture). The use of appropriate footwear is imperative: both high heels (which accentuate hyperlordosis and shift the center of gravity further forward) and completely flat shoes (which do not support the plantar arch) are discouraged. Ideal footwear has a wide heel of 2-3 centimeters, a cushioning sole, and good heel containment.

In domestic and work activities: Lifting heavy loads should be avoided. If it is unavoidable to pick up an object from the ground, it is necessary to bend the knees while keeping the spine in a neutral position, bringing the object close to the body before standing up. Activities that require asymmetrical hip abduction (such as getting out of a car, pushing heavy objects with one foot, or dressing while standing) must be modified: to get out of the car, for example, it is advisable to keep the knees together and rotate the pelvis as a block outwards before placing the feet on the ground.

Postpartum Recovery and Tissue Normalization

A clinical aspect of fundamental importance concerns the persistence of ligamentous laxity in the postpartum period. Hormone levels do not immediately return to zero after childbirth. Scientific literature indicates that joint hypermobility can persist for a variable period of 3 to 6 months postpartum (Aldabe et al., 2012). This period may be further prolonged in breastfeeding women, due to the interaction between prolactin and other hormones that maintain a certain degree of tissue laxity.

During this transition phase, the musculoskeletal system is particularly vulnerable. The pelvis, which has undergone maximum mechanical stress during labor and delivery, needs time to regain its intrinsic stability. It is a common mistake to prematurely resume high-impact sports activities (such as running, CrossFit, or aerobics) in the first weeks after childbirth. Such behavior exposes the new mother to a high risk of pelvic organ prolapse, urinary incontinence, chronic lumbopelvic pain, and peripheral joint injuries.

The postpartum rehabilitation pathway must be gradual, progressive, and constantly monitored by the doctor or physical therapist. The initial priority is the recovery of pelvic floor and abdominal wall competence (assessment and treatment of diastasis recti). Only subsequently, and after evaluating joint stability, will it be possible to reintroduce greater loads and high-impact cardiovascular activities.

FAQ: Frequently Asked Questions about Hypermobility in Pregnancy

How long does the effect of ligamentous laxity last after childbirth?

Ligamentous laxity does not disappear immediately after the baby’s birth. Connective tissues generally take 3 to 6 months to regain their normal stiffness and resistance. In breastfeeding women, due to the particular hormonal balance, this period can be prolonged. During these months, it is essential to gradually resume physical activity, under the supervision of the doctor or physical therapist, avoiding high-impact sports that could cause trauma to still unstable joints.

Does hypermobility in pregnancy always cause pain?

No, hypermobility is a physiological condition necessary for childbirth and does not automatically translate into pathology or pain. Pain arises when the neuromuscular system is unable to adequately compensate for the loss of stability provided by the ligaments, leading to mechanical overloads, joint inflammation, or muscle spasms. Good prior muscle tone and the adoption of correct ergonomic rules significantly reduce the risk of developing painful symptoms.

Which sports or physical activities are not recommended due to ligamentous laxity?

Due to reduced joint stability, all contact sports (martial arts, basketball, soccer), sports involving jumps or sudden changes of direction (volleyball, tennis, skiing), and high-impact activities such as intense running or maximal weightlifting are strongly discouraged. Disciplines that require extreme joint stretching (such as some advanced yoga positions or rhythmic gymnastics) should also be avoided, as they could overstretch already lax ligaments, causing micro-injuries. Low-impact activities such as swimming, walking, cycling, and adapted clinical Pilates are recommended instead.

Is stretching useful for relieving joint and muscle pain during pregnancy?

Stretching during pregnancy must be performed with extreme caution. Since ligaments are already loosened, forcing stretching to the maximum degrees of joint excursion (end-range stretching) is dangerous and can worsen instability. It is preferable to focus on gentle and dynamic mobility exercises, or on myofascial release techniques to relieve muscle tension. Any flexibility exercise program must be structured and approved by the doctor or physical therapist to ensure maximum safety for the mother and fetus.

Does the use of a pelvic band or belt weaken the muscles?

If used correctly and according to clinical indications, the pelvic belt does not cause muscle hypotrophy. Its purpose is to provide temporary passive stability during loading activities (such as walking or standing for long periods), allowing the muscles to work in a more favorable and less painful biomechanical environment. It should not be worn 24 hours a day, but only during moments of greater mechanical stress. The use of the support must always be accompanied by an active strengthening exercise program prescribed by the doctor or physical therapist.

Frequently Asked Questions

What is the primary role of relaxin during pregnancy?

Relaxin is a peptide hormone primarily secreted by the ovarian corpus luteum, decidua, and placenta during gestation. Its fundamental action is to induce generalized ligamentous laxity, which is physiologically indispensable for accommodating fetal development and preparing the pelvis for childbirth.

How does relaxin contribute to musculoskeletal changes during pregnancy?

Relaxin’s action on connective tissues leads to a state of increased joint laxity throughout the body. This phenomenon can result in joint hypermobility, altering the stability of the musculoskeletal system.

What are the potential risks associated with relaxin-induced joint hypermobility?

Joint hypermobility caused by relaxin can expose pregnant individuals to a greater risk of developing painful dysfunctions, biomechanical overloads, and postural alterations. These changes can impact overall comfort and physical function during pregnancy.

Why is understanding relaxin’s effects important for healthcare management during pregnancy?

Understanding the mechanisms through which relaxin acts on connective tissues is essential for developing adequate prevention and clinical management strategies. This knowledge allows for personalized and safe evaluation and treatment pathways supervised by qualified healthcare personnel, such as a doctor or physical therapist.

Sources and Scientific References

1. Aldabe, D., Ribeiro, D. C., Milosavljevic, S., Dawn, A. S., & Sole, G. (2015). Pelvic girdle
2. Bulguroglu M et al. (2025). Effectiveness of a prenatal pilates program on ligamentous laxity and joint hypermobility in pregnant women: a dual-center randomized controlled trial. BMC Pregnancy Childbirth. 25:897. DOI | PubMed
3. Em S et al. (2015). Serum relaxin levels in benign hypermobility syndrome. J Back Musculoskelet Rehabil. 28:473-9. DOI | PubMed
4. Wolf JM et al. (2014). Relationship of relaxin hormone and thumb carpometacarpal joint arthritis. Clin Orthop Relat Res. 472:1130-7. DOI | PubMed
5. Kapila S et al. (1998). Targeted induction of collagenase and stromelysin by relaxin in unprimed and beta-estradiol-primed diarthrodial joint fibrocartilaginous cells but not in synoviocytes. Lab Invest. 78:925-38. PubMed
6. Wolf JM et al. (2013). Relationship of serum relaxin to generalized and trapezial-metacarpal joint laxity. J Hand Surg Am. 38:721-8. DOI | PubMed