The hormone everyone blames, and how long it is really there
You have probably been told relaxin sticks around for months, or for as long as you breastfeed. The measured evidence tells a different story, and it changes what you should worry about.
Quick answer
Relaxin falls fast. It is made mainly by the corpus luteum and, in pregnancy, by the placenta, so once the placenta is delivered the main supply is gone and circulating levels drop back toward non-pregnant levels within days rather than months. The widely repeated claims that relaxin stays high for five months, or for as long as you breastfeed, are not supported by measured hormone data. Breastfeeding is driven by prolactin and oxytocin, not relaxin. If your joints still feel loose or sore months later, that is real, but relaxin is almost certainly not the reason, and it is not a reason to delay gentle core and pelvic floor work.
not months, is how quickly circulating relaxin typically returns toward non-pregnant levels once the placenta is delivered
is the standard postnatal check in the UK, and the usual point at which a gradual return to exercise is discussed (NHS)
of mums still had diastasis recti at 12 months postpartum, long after relaxin has normalised (Sperstad et al., British Journal of Sports Medicine, 2016)
What relaxin actually does
Relaxin is a peptide hormone. In pregnancy it is produced mainly by the corpus luteum, with the placenta and the lining of the uterus contributing as well. Its job is to help your body accommodate a growing baby and prepare for birth: it softens connective tissue, contributes to the loosening of the ligaments around the pelvis, and plays a role in the changes to the cervix before labour.
Levels are not steady across pregnancy. Circulating relaxin rises early and peaks around the end of the first trimester, dips through the middle of pregnancy, then rises again toward term. That first-trimester peak surprises a lot of mums, because the joint aches most people associate with relaxin tend to arrive much later, when a growing bump has changed how you stand and load your hips.
How fast it falls after birth
This is the part that gets misreported. The placenta is a major source of relaxin, and once it is delivered that source disappears. Relaxin does not linger in the bloodstream for long, so measured levels drop steeply in the hours and days after birth and return toward the non-pregnant range within a matter of days.
So by the time you are at your six-week check, relaxin is not what is holding you back. Whatever you are feeling in your hips, pelvis or lower back at that point has other explanations, and most of them are more fixable than a hormone. Our guide to postpartum back and hip pain goes through the usual culprits.
The five-month claim, and the breastfeeding claim
Two versions of the same myth circulate constantly in postnatal fitness spaces. The first says relaxin stays elevated for around five months after birth. The second says it stays elevated for as long as you breastfeed, sometimes phrased as a warning not to stretch or lift while nursing.
Neither holds up when you look at what is actually measured. Lactation is driven by prolactin and oxytocin. Neither of those is relaxin, and breastfeeding has not been shown to keep relaxin elevated. The five-month figure appears to be an oversimplification of research into how long joint laxity and pelvic pain can persist, which is a different question from how long the hormone is in your blood.
The practical harm here is real. Mums are told to wait, sometimes for the better part of a year, on the basis of a hormone that left weeks ago. That delay does not protect anything, and it costs you months of the gradual loading that connective tissue actually needs.
If relaxin is gone, why do my joints still feel loose?
Because joint stability is not only a hormone story. Several things persist well past the point where relaxin has normalised.
- Tissue remodelling takes time. Ligaments and fascia that stretched over nine months do not snap back the week the hormone leaves. The linea alba, the connective tissue seam down the front of your abdomen, is a good example: it regains tension gradually, over months.
- Muscles are deconditioned. A lot of what feels like a loose joint is a joint that is not being supported well, particularly around the pelvis and hips.
- Your loading pattern changed. Feeding positions, carrying a baby on one hip, and broken sleep all alter how you stand and move.
- Symptoms and hormone levels do not track together. Research into pregnancy-related pelvic girdle pain has not found a consistent relationship between measured relaxin and how much pain a woman reports, which is a strong hint that other factors are doing the work.
What this means for your recovery
The useful takeaway is that your timeline should be built around healing tissue, symptoms and gradual load, not around waiting for a hormone to clear. That is a much more encouraging framing, because it means progress is something you influence rather than something you wait out. Our realistic postpartum recovery timeline lays out what the first year usually looks like, and if abdominal separation is your main concern, the diastasis recti healing timeline covers when the gap tends to narrow.
Start with breathing and gentle deep core work rather than nothing, and build from there. When it comes to specific methods, be sceptical of anything sold as a shortcut. Our review of whether hypopressives work for diastasis recti is a good example of separating a technique from the marketing around it. For pacing your first weeks back, see when you can start working out after giving birth.
None of this replaces being assessed. If you have pelvic pain, a feeling of instability, leaking, or a sense of heaviness, a women's health physiotherapist can tell you far more in one appointment than any hormone timeline will. Results vary from mum to mum.
The short version
Relaxin is a pregnancy hormone, not a postpartum one. It clears within days of the placenta being delivered. Anything you are still feeling at three, six or twelve months is about tissue, strength and habits, all of which respond to sensible, progressive work. Stop waiting for a hormone to leave. It already has.
A plan built around healing, not hormone myths
Mumma Glow makes affordable, one-time digital guides for mums who want the whole picture in order: breathing, deep core, pelvic floor, glutes and energy. The Complete Postpartum Body Reset bundle is $50 for all of it, individual guides start at $15, and code GLOW20 takes 20% off. No subscription, no monthly fee, yours to keep and reuse. It is the budget alternative to programs like MUTU. This is education rather than medical treatment, and results vary from mum to mum.
Frequently asked questions
Does relaxin stay in your body while breastfeeding?
No. Breastfeeding is driven by prolactin and oxytocin, and there is no good evidence that nursing keeps relaxin elevated. Circulating relaxin falls back toward non-pregnant levels within days of the placenta being delivered, whether or not you breastfeed.
Is it true relaxin lasts five months after birth?
That figure is not supported by measured hormone data. It seems to have come from research into how long joint laxity and pelvic pain can last, which is a separate question from how long the hormone circulates. Laxity and symptoms can persist for months. Relaxin does not.
Should I avoid stretching because of relaxin?
Not on the basis of relaxin alone, especially after the first few weeks. The sensible caution is about pushing into extreme end-range stretching while your tissue is still remodelling and your muscles are deconditioned, which is a reason to progress gradually rather than a reason to avoid movement.
Why do my hips still feel unstable at six months postpartum?
Usually a mix of connective tissue that is still remodelling, deconditioned muscles around the pelvis, and changed daily loading from carrying and feeding. Those all respond to progressive strength work. If it is painful or getting worse, see a women's health physiotherapist.
Can I start core work before relaxin has cleared?
In practice this question does not arise, because relaxin clears within days while most mums are not doing meaningful core work that early. Follow your postnatal check and your symptoms instead, and start with gentle breath-led deep core work once you have been cleared.
Sources: Sperstad JB, Tennfjord MK, Hilde G, Ellstrom-Engh M, Bo K. Diastasis recti abdominis during pregnancy and 12 months after childbirth. British Journal of Sports Medicine, 2016. NHS, Your postnatal check, and Pelvic pain in pregnancy. Cleveland Clinic, Relaxin. American College of Obstetricians and Gynecologists (ACOG), Physical Activity and Exercise During Pregnancy and the Postpartum Period.
This article is general education, not medical advice. Mumma Glow is not affiliated with any of the programs or organisations named here. Results vary from mum to mum. If you have pelvic or joint pain, a feeling of instability, leaking or heaviness, please speak to your GP, midwife or a women's health physiotherapist.