Relaxin is a hormone produced in the bodies of both men and women. Just as the name suggests, the ‘relaxin’ hormone promotes relaxation in the body.
The relaxin hormone helps to loosen joints, muscles and ligaments. It’s also responsive to environmental stressors and plays a role in stress reduction.
Relaxin hormone levels increase substantially during pregnancy. The effects during pregnancy help soften the abdominal muscles to accommodate the growing baby and prepare a woman’s body for labor and birth.
The levels of relaxin hormone are high after giving birth, and relaxin while breastfeeding remains elevated in mothers through their breastfeeding journey.
What Is the Relaxin Hormone?
The relaxin hormone surges during pregnancy and breastfeeding. It’s responsible for relaxing your pelvic ligaments and muscles during childbirth to facilitate delivery. But it may also impact you while breastfeeding.
Relaxin levels remain elevated for several months after giving birth as your body returns to its pre-pregnancy state. This means your joints and ligaments are more flexible, which could lead to instability and pain.
Relaxin also causes uterine contractions that can stimulate breast milk production. These contractions, known as “afterpains,” tend to be more noticeable when breastfeeding and usually subside within a week of delivery.
Elevated relaxin may influence your mood and stress levels. Some mothers report feelings of anxiety or irritability, while others experience a sense of well-being from breastfeeding. Getting extra rest, limiting stress, and talking to others can help you cope during this transition.
Relaxin levels will return to normal a few months after you stop breastfeeding. Though its effects are temporary, relaxin plays an important role in preparing and sustaining you for this new stage of motherhood.
When are levels of the relaxin hormone highest?
Other than during pregnancy, relaxin is also produced during your menstrual cycle. The role of relaxin during your menstrual cycle is to soften the uterus and prepare the lining for implantation of an embryo.
Relaxin levels are highest during the second half of your cycle. If implantation occurs, relaxin levels remain high and continue to rise in early pregnancy until the end of the first trimester. Relaxin levels decrease after the first trimester of the pregnancy but remain for the duration of the pregnancy and beyond.
If conception does not occur during a menstrual cycle, the level of relaxin drops until the second half of the next cycle.
You can read more about the menstrual cycle in BellyBelly’s article Menstrual Cycle – Stages, Phases and What To Expect.
Relaxin is also produced in the placenta during pregnancy. High levels of relaxin stop the uterus from contracting, which would result in preterm labor.
What is the role of relaxin hormone in the postnatal period?
We know about the role relaxin plays for pregnant women, but what about post pregnancy relaxin?
In the postpartum period, there are many hormonal changes. Two of the main pregnancy related hormones – estrogen and progesterone – decrease; levels of hormones that support breastfeeding – oxytocin and prolactin – increase.
Although the level of relaxin decreases after the first trimester of pregnancy, it is believed to be present in increased levels in the body for up to 12 months postpartum.
Some studies suggest that relaxin can help heal injuries, reduce inflammation, relax blood vessels, increase blood flow and lower blood pressure.
Why does your body produce relaxin while breastfeeding?
The reason the level of relaxin remains elevated in the postpartum period, particularly during lactation, is because of the important role it has in breast tissue development and function. Relaxin is a hormone that’s also present in breast milk.
In animal studies, it has been shown that the relaxin in the colostrum that is taken up in the gastrointestinal tract of offspring enters circulation and has a specific physiological and epigenetic effect on the female reproductive system.
The exact role that relaxin plays in human milk is still being studied; however, we know that postpartum relaxin remains higher in women who are breastfeeding compared with women who aren’t.
Can you have too much relaxin?
Although the research is limited, it is possible to have too much or too little relaxin hormone.
There’s evidence to suggest that endometriosis might be associated with lower levels of relaxin.
For more information on endometriosis, you can read BellyBelly’s article Endometriosis Symptoms | Do You Have Endometriosis?
Small studies have found that higher levels of relaxin could cause premature rupture of membranes, leading to premature labor.
For more information on premature labour, you can read BellyBelly’s article Preterm Labor | All You Need To Know.
More research is needed on the effects of high or low relaxin hormone levels in the body.
Does relaxin affect breast milk production?
Studies have found that relaxin stimulates the secretion of prolactin from the pituitary gland in the brain.
Prolactin, sometimes referred to as the ‘milk-making hormone’, is one of the main hormones involved in the development of mammary tissue (mammary glands) and the production of breast milk.
Low levels of prolactin are associated with low breast milk supply; however, further research is needed to ascertain whether low relaxin levels have the same effect.
Can relaxin cause pelvic girdle pain?
Although relaxin is effective in softening and loosening your body for pregnancy and birth, the relaxing of the muscles around the pelvis, lower back and abdomen can cause pelvic pain for some women.
This is referred to as pregnancy related pelvic girdle pain (PGP). Symptoms of PGP might include:
- Pelvic or lower back pain
- Hip joint pain
- Shooting pains down one or both legs
- Feeling of weakness or instability in the pelvic floor region.
You can read more about this in BellyBelly’s article Pelvic Girdle Pain During Pregnancy | Symptoms and Treatment.
See your healthcare provider for advice if you are experiencing any of these symptoms.
What is the impact of relaxin hormone on the pelvic floor muscles?
The pelvic floor muscles are located between the tailbone and pubic bone and support the bowel, bladder and uterus. Due to the loosening effects of relaxin on the body, the connective tissue that holds these organs is place can become lax. This is also due to the extra demands made on the pelvic floor muscles throughout pregnancy and childbirth.
Weakening of the pelvic floor muscles can affect bladder and bowel control or lead to other problems, such as sexual dysfunction.
In terms of postpartum exercise routine, breastfeeding mothers should take extra care. Choosing gentle movements that avoid overstretching can help prevent injuries or further weakening of the pelvic floor muscles that can occur due to increased relaxin in the body.
Managing the Effects of Relaxin While Breastfeeding
The hormone relaxin, which helps relax your ligaments and joints during pregnancy and childbirth, remains elevated while you’re breastfeeding. This can lead to some temporary side effects you’ll want to be aware of.
Joint laxity and instability
Relaxin causes your joints and connective tissue to remain loose, which often results in feelings of instability or hypermobility in your knees, hips, and back. Be careful with any high-impact exercises during this time and avoid movements that cause pain. Low-impact options like walking, swimming or yoga are good alternatives.
Muscle aches and strains
Your loosened joints and tendons also make you more prone to strains, sprains and muscle aches. Gentle stretching, massage therapy or over-the-counter pain medication can help relieve discomfort. Apply ice and give the affected area extra rest as well.
Difficulty losing the “baby weight”
Relaxin slows your metabolism and makes it more challenging to lose pregnancy weight. Focus on eating a healthy, balanced diet with moderate portions, and stay hydrated. Losing about weight at a safe rate should be the focus. Don’t get discouraged if the scale isn’t dropping as quickly as you’d like. Your body is still adjusting, and every woman’s timeline for weight loss is different.
For more information, you can read Relaxin Hormone | Effects On Conception, Pregnancy And Birth.