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Pregnancy Conditions··Updated: March 3, 2026

Relaxin hormone: How it affects your body during pregnancy

Relaxin hormone supports your body during pregnancy by loosening joints and improving blood flow. Discover its effects and when to consult your doctor.

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Relaxin hormone and your body during pregnancy 🤰

The relaxin hormone plays a key role in pregnancy, helping your pelvis and joints become more flexible, supporting healthy blood flow, and preparing your body for labor. Relaxin levels rise especially in the first and second trimesters, triggering many changes that help your body adapt to carrying a baby.

Many expectant mothers notice the effects of relaxin hormone, such as increased flexibility, joint instability, or even discomfort. These changes are a normal part of pregnancy, and without relaxin, giving birth would be much more difficult.

What is the relaxin hormone?

Relaxin is a protein hormone produced mainly by the ovaries, placenta, and uterus. During pregnancy, relaxin levels increase significantly, especially in the first trimester. Its main job is to loosen the ligaments and joints in the pelvis, making room for your growing baby and easing the birth process.

How does relaxin hormone work?

Relaxin makes connective tissues, ligaments, and joints more flexible. This allows the pelvis to widen as your baby grows and helps with dilation during labor. Relaxin also affects blood vessels, improving circulation to support your baby’s oxygen and nutrient needs.

What changes does relaxin hormone cause in the body?

The effects of relaxin hormone include:

  • Loosening of joints and ligaments
    Ligaments around the pelvis, hips, and lower back become more flexible, which helps with childbirth but can also cause instability.

  • Increased flexibility
    Not just the pelvis—other joints like knees and ankles may feel looser, raising the risk of sprains or strains.

  • Support for circulation
    Relaxin widens blood vessels, lowers blood pressure, and improves blood flow to the uterus, placenta, and kidneys.

  • Digestive system effects
    Relaxin can relax muscles in the digestive tract, sometimes leading to bloating or heartburn.

Everyday examples: What might you notice?

  • Lower back or hip pain
    As the pelvis loosens, you may feel more sensitive in your lower back and hips, especially later in pregnancy.

  • Unstable knees or ankles
    Activities like walking, exercising, or sudden movements may lead to sprains or minor injuries more easily.

  • Greater flexibility
    Some moms notice they’re more flexible, but this isn’t always comfortable—joints may feel less stable.

  • Lower blood pressure, dizziness
    Widened blood vessels can cause mild drops in blood pressure, sometimes leading to dizziness.

Possible risks and side effects

While relaxin hormone is essential for pregnancy, it can bring some risks:

  • Joint injuries
    Looser ligaments mean a higher chance of sprains, strains, or other joint injuries.

  • Pain and instability
    Pelvic, lower back, or knee pain and instability are common complaints.

  • Varicose veins, swelling
    Widened blood vessels can make you more prone to varicose veins or swollen legs.

  • Digestive issues
    Bloating, heartburn, or constipation may occur due to relaxin’s effects.

Medical background: Why do we need relaxin hormone?

Relaxin hormone is important from an evolutionary perspective—it allows the pelvis to widen, making room for your baby and easing labor. Relaxin also helps relax the muscles of the uterus, reduces contractions, and supports healthy fetal development.

By widening blood vessels, relaxin improves circulation, which is vital for delivering oxygen and nutrients to your baby. It also boosts blood flow to the kidneys, helping your body manage fluids during pregnancy.

When should you see a doctor?

Most changes caused by relaxin hormone are normal, but you should seek medical advice if:

  • Severe joint pain or instability
    If pain limits your movement or a joint feels abnormally loose, contact your doctor.

  • Unusual swelling or inflammation
    Swelling, redness, or warmth in a joint may be a sign of inflammation.

  • Injury, sprain, or dislocation
    If you experience an injury or a joint moves out of place, get professional help.

  • Persistent dizziness or low blood pressure
    If your blood pressure drops too low or you feel dizzy often, consult your healthcare provider.

How can you ease the effects of relaxin hormone?

  • Avoid sudden movements
    Move slowly and carefully, especially when exercising or lifting.

  • Choose supportive footwear
    Good shoes help prevent ankle injuries.

  • Support your joints
    Use a maternity belt or knee brace if needed.

  • Prioritize rest
    Proper rest helps your body recover.

  • Consult a specialist
    A physical therapist or OB-GYN can recommend safe exercises and movement strategies.

Supportive thoughts for your pregnancy journey 🌸

The effects of relaxin hormone can feel strange or even worrying, but these changes are your body’s natural way of adapting to pregnancy. If you’re unsure, don’t hesitate to reach out—professionals are here to help. Every pregnancy is unique, and the impact of relaxin hormone varies from person to person. Listen to your body and give yourself time to adjust.

For more tips, expert guidance, and support, check out our free app for even more helpful information.

Frequently Asked Questions

What is the relaxin hormone?+

Relaxin is a protein hormone produced mainly during pregnancy. It helps your body adjust to the changes of pregnancy.

How does relaxin hormone affect the joints?+

Relaxin loosens ligaments and joints, especially in the pelvis, to prepare for childbirth. This can increase the risk of joint injuries.

When should I see a doctor about relaxin hormone symptoms?+

If you experience severe joint pain, instability, or unusual swelling, it's important to consult a healthcare professional.

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