Ageing, Genetics and Collagen: Why Some Women Are More Prone to Laxity

Two women can have the same number of children, the same kind of births, the same age and much the same life, and end up in very different places. The unspoken explanation is usually that the second one did something wrong: skipped the exercises, went back to running too soon, left it too long. That explanation is almost always false, and there is now a good body of evidence explaining why.

A substantial part of how your pelvic tissue behaves was settled before you were born. Not all of it, and not enough to make anything inevitable, but considerably more than most women are ever told. This article is about that inherited component: what collagen does in the pelvis, how much of the difference between women is genetic, the two genes identified by name, and what a family history is genuinely useful for. It also answers the question anyone reading about collagen ends up asking, which is whether a supplement helps.

The scaffolding, and why it varies

Laxity is a sensation of vaginal looseness or reduced tightness, and it is not prolapse: with laxity alone, no organ is descending or bulging. Hold on to that distinction, because it becomes important once the genetics arrive.

Support in the pelvis comes from two structures. The first is muscle: the levator ani, slung across the base of the pelvis. The second is connective tissue: the endopelvic fascia, a mesh of collagen interlaced with elastin, smooth muscle, fibroblasts and blood vessels, anchoring the bladder, urethra, vagina and uterus to the pelvic walls. That mesh runs in three levels: vertical fibres suspending the upper vagina and cervix, a lateral hammock across the mid-vagina, and a lower level fused with the levator ani and the perineal body. Damage at each level produces a different pattern.

The connective tissue is where inheritance does most of its work. Collagen makes up 70 to 80 percent of connective tissue, and it comes in types that do different jobs. Type I provides mechanical strength. Type III provides elasticity and extensibility, the capacity to stretch and come back. Type IV forms the basement membranes. The collagen and elastin around the urethra even contribute passively to holding it closed, with no muscle involved at all.

You do not build those proteins to a universal specification. The genes coding for them vary between people, and so does the tissue that results. Two women can put the same load through the pelvis and get different answers, because they started with different material.

How much of this is inherited

More than the conversation around it suggests.

Take the twin figure first, and read it precisely. It is 40 percent of the variation between women, not 40 percent of any individual woman’s situation. When you line women up and ask why they differ, a large slice of the answer is inherited.

Then read the sister row twice. Those were women who had never given birth, compared with their own sisters who had, and their prolapse stage matched in three quarters to nine tenths of cases. Vaginal birth is the single largest mechanical factor in pelvic floor change, and in that comparison it barely separated them. What the sisters shared was not obstetric history.

One honest caveat, and it is a real one. Almost all of this research is on pelvic organ prolapse rather than on vaginal laxity specifically, and those are clinically distinct conditions. They rest on the same scaffolding, which is why the findings carry over, but a heritability figure for prolapse is not automatically one for laxity. Anyone quoting these numbers at you about laxity, this article included, is making an inference. It is a reasonable one. It is still an inference.

The genes with names, and why the mice matter

Two genes come up repeatedly.

COL3A1 codes for Type III collagen: the elastic type, the one responsible for stretch and recoil. A specific variant of it, rs1800255, disrupts the structure of that protein and carries an odds ratio of around 5 for prolapse. For a single variant, that is a large effect.

FBLN5, an elastic-fibre gene, is the second. Variants in it are also implicated.

Association findings on their own would not be enough to hang much on: genes travel with other genes, and links of this kind often dissolve later. What lifts this above correlation is the animal work. In knockout-mouse models, where the gene in question is deliberately switched off, the result is vaginal wall dilation. Remove the gene, get the tissue change. That is a causal chain rather than a statistical coincidence, and it is why this section can be written with more confidence than most material on this subject.

What age adds on top

Genetics sets the starting material. Age and hormones then act on it, and those are separate contributions rather than the same one described twice.

Menopause is independently associated with laxity. In one cross-sectional study, 52.6 percent of women reporting laxity were postmenopausal, with adjusted odds of 2.23 compared with women who were not. The mechanism is oestrogen: its decline is linked to atrophy of genitourinary tissue and to altered expression of the genes that build and maintain the vaginal wall’s extracellular matrix, the collagen and elastin scaffolding described above.

That last point connects the two halves of this article. Your inherited collagen genes are not a fixed setting. How strongly they are expressed shifts with your hormonal state, so a woman who started with a tendency towards more extensible tissue is not carrying a constant: the maintenance system underneath it changes. Increasing age is listed by NICE among the non-modifiable risk factors for pelvic floor dysfunction, alongside family history. The hormonal side of this is a large subject in its own right and deserves more room than it can have here.

The collagen supplement question

If you have read this far, you have almost certainly had the thought: the problem is collagen, so take collagen.

It is a reasonable inference, and the evidence does not support it. No peer-reviewed randomised controlled trial has been found linking dietary or collagen supplementation to preventing vaginal laxity. Not a trial with a disappointing result. No trial. That is an absence of evidence rather than proof of no effect, and the distinction is worth keeping, but nobody selling a collagen product for this purpose can point to a study, because there is not one.

NICE does give dietary advice for pelvic floor health, and it is worth knowing exactly what it says, because it gets stretched. NICE advises that physical activity and a healthy diet can help prevent pelvic floor dysfunction, and the dietary content of that is general: adequate fibre, adequate fluids, weight management. It is not collagen-specific, and NICE does not cite evidence for collagen supplementation as a preventive measure.

There is also a plausibility problem worth naming. Nothing in the research above describes a shortage of raw material. It describes differences in how the protein is built and assembled. Whether swallowing more of the finished product changes that is precisely the question no trial has answered.

What a family history is actually good for

Non-modifiable does not mean useless.

NICE formally separates modifiable pelvic floor risk factors from non-modifiable ones, and family history sits in the second group: specifically a family history of urinary or faecal incontinence or overactive bladder, alongside increasing age, gynaecological surgery and chronic cough. Being on that list means the risk is recognised, not that it is irrelevant.

It matters because of a gap in the system. RCOG notes that although the 2021 NICE evidence review identified these risk factors, there is still no national guidance on which women are at greatest risk, or on which interventions reduce it, and it is calling on policymakers to close that gap. Until that happens, nobody is reviewing your family and flagging you. If it gets raised, you will be the one raising it.

So raise it, and be specific. Who in your family, what happened, roughly what age it started, and whether it followed a birth or arrived independently of one. That is a different kind of appointment from a vague sense that something feels different.

Some things go ahead of all of this. Unexplained bleeding, unusual or foul-smelling discharge, pelvic pain, a sensation of heaviness or dragging, persistent incontinence or an overdue cervical screening all need a GP or gynaecologist, and they need one first. A bulge or a dragging sensation is not laxity. It points towards prolapse, which is a medical assessment rather than a cosmetic one.

Around 40 percent of the variation being inherited means something quite specific. A large part of where you have ended up was never a decision you made.

The most useful thing to do with all of this is unremarkable and well evidenced. Pelvic floor muscle training has excellent trial evidence for stress incontinence, though not for reversing laxity itself, and NICE advises physical activity and a healthy diet for pelvic floor health generally. A known family history is a reason to start earlier and take the technique seriously, not a reason to give up on it.

If you have ruled out the medical possibilities and want an honest assessment of where you actually are, a consultation with our practitioners is a reasonable next step. Ask what the evidence for any option does and does not show, and expect a straight answer. What nobody should be telling you is that this is the consequence of something you neglected. A good part of it was written down before you had any say in the matter.