Just when you thought the pressure on mothers couldn’t be any greater, science and the media machine that interprets it have come up with a brand new Darwin-shaped stick to beat us with. According to a “simple mathematical model” published this week, the rising rate of caesarean sections could be explained by an evolutionary trend whereby the procedure itself perpetuates small pelvises in women.

Babies who would previously have died during childbirth because they were unable to fit their large heads through their mothers’ narrow pelvises are now saved by caesarean sections. According to the theory, the small-pelvis genes of the mother are then passed on to the next generation, defying natural selection. Researchers predict that this will lead to an evolutionary loop requiring increasing numbers of caesareans as the generations go by.

It makes sense that dramatic and persistent changes to the way we give birth will have an impact on the way our species develops. But I find myself irked by the narrow and inaccurate slice of the evolutionary pie the study has chosen (reflective of a broader trend in how contemporary childbirth is understood).

This research is based on an assumption that, while foetuses grow larger to increase their chances of survival (as low-birth weight is associated with poor outcomes), women’s bodies have somehow malfunctioned. It takes for granted that reporting of cephalopelvic disproportion is accurate and scientific, and ignores the myriad other factors at work. None of these assumptions stand up.

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Despite this, the paper has been widely reported, becoming another weapon in the polarising media fight involving women’s bodies and the medical establishment.

With predictable regularity, every time the caesarean rate is mentioned, women are blamed: women, with their irrational desires to give birth when they are too old, too fat, or their bodies are otherwise addled by the irresponsible things they’ve done to them prior to becoming human incubators.

In the current, divisive climate around women’s choices in childbirth, it’s easy to take the step forwards from conjecture to another layer of guilt and pressure on women to do better or risk the future of the human species. One article reporting on the study used the phrase “too posh to push”.

But are women’s bodies really malfunctioning with increasing regularity, and is that why the caesarean section rate is rising? The short answer is no. As the paper itself admits, there’s no standardised way of measuring, recording or tracking suspected cases of a narrow pelvis/large head. There have been attempts to use shoe size, x-rays and scanning technology to predict the phenomenon, but these have been largely unsuccessful, demonstrating that pelvis size isn’t in itself a useful predictor of a difficult birth.

Many women are told their bodies have failed to make a path for the babies they have grown. But in this study, 68% of women diagnosed with absolute cephalopelvic disproportion in a previous pregnancy went on to have a vaginal birth in future. True cephalopelvic disproportion is very rare, reserved in the main for women with pelvic damage and those (largely in the developing world) suffering from malnutrition. The paper is based on a measurement that’s often little better than a whim created by an obstetric culture that was (and sometimes still is) steeped in the idea that women’s bodies don’t work, and which has the language to prove it: “incompetent cervix”, “failure to progress”, “lack of maternal effort”.

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But caesarean rates have escalated way beyond what can be explained by cephalopelvic disproportion, even taking at face value the specious figures (which estimate instances of CPD were 30 in 1,000 births in the 1960s and are 36 in 1,000 births today).

Childbirth practices have altered almost beyond recognition in the past 100 years. Birth has been brought into hospital after being largely a community-based event. Medical intervention and expertise have increased, bringing with them many life-saving interventions and huge progress but also some side-effects. Low-birth weight infants are far more likely to survive. Women have fewer children each but more multiple births. And maternal nutrition is far better, at least in the developed world. The paper is seemingly blind to these and many other interrelated factors.

The theory is also strangely quiet on the dramatic impact of place of birth on intervention rates. The 2011 Birthplace in England study, which looked at about 60,000 births, highlighted that – far beyond the fractional impacts of rapid evolution – our maternity system and obstetric practice lead to unnecessary interventions.

More than 40% of low-risk women who give birth in hospital (where the vast majority of women give birth in the UK) face a caesarean or instrumental birth, but for a woman with the same risk-profile who plans to give birth at home, that risk drops to 10%. Caesarean rates are often driven by factors outside the woman – not by a failure of her skeleton.

I regularly fight for women who want or need caesareans to have access to them, and know that a focus on caesarean rates can impact negatively on the women who need them most. But for most women, keen to have as uncomplicated a birth as possible, current practice often leads to a caesarean that they may not have needed yet will probably be reported as a failure within their bodies rather than the system.

This is not good enough. The issue is not whether caesareans or vaginal birth are safer, better, or more likely to lead to an uncomplicated future for humanity, but simply that women matter during childbirth. Many faced intervention they didn’t need and wanted to avoid, while others struggled to get a caesarean that would make birth feel safe for them.

Skewed research of this kind adds little to our knowledge base but feeds the damaging media appetite for woman-blaming and dichotomised depictions of childbirth that are a weighty burden for new mothers to bear.