Growth scans were originally introduced into maternity care with a specific and perhaps surprising to modern ears, purpose: to identify babies who were genuinely small for gestational age (SGA) or experiencing fetal growth restriction.
The 'big baby' diagnosis was a secondary by-product, an unintended side effect, but one that has and is increasingly syphoning women and birthing people onto the conveyor belt of the birth factory.
From "Too Small" to "Too Big"
Many of my clients have had this exact, frustrating scenario play out:
A woman attends a routine appointment, where their bump is measured with a tape measure. The midwife tells them that their fundal height is measuring small and recommends an urgent growth scan. So off they go. They walk into that scan appointment anxious about growth restriction, only to walk out with a diagnosis of a large baby, and with that with no apparent critical thinking on behalf of the medical professionals an immediate recommendation for an early induction.
Which one is it? How does a bump go from being suspiciously small on a tape measure to dangerously large on an ultrasound in the space of 48 hours? and why does no-one NO-ONE employed by the medical complex ask that question. The machine says it - it MUST be true. It would be laughable if it weren't so damaging.
What the Big Baby Trial Actually Showed...
A few years ago now the UK’s Big Baby Trial was published in The Lancet. Local women and birthing people may well have been part of that study which aimed to see if offering early induction between 38 weeks and 38 weeks and 4 days for suspected Large for Gestational Age (LGA) babies reduced shoulder dystocia.
The results were hailed as a success BUT:
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60% Error Rate: Around 60% of the babies suspected of being 'big' on scan were not big when they were born. Six out of ten families faced pressure to induce for a baby of completely normal weight, and this continues, the scans have not got more accurate!
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No Statistical Difference in the Main Goal: In the gold-standard analysis, early induction did not show a statistically significant reduction in shoulder dystocia. The trial was actually stopped early because the rate of shoulder dystocia was far lower than expected across the board.
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Tiny Weight Differences, Higher Care Needs: Induced babies were on average only about 200g lighter (the weight of an avocado), but they had a higher rate of admission to neonatal care. Trading a marginal, unproven reduction in physical risk for a very real increase in neonatal intervention.
How can you navigate this if it arises in your pregnancy?
Your body is not a faulty machine that suddenly forgets how to give birth because a scan, which is wrong more than half the time, estimated a weight.
My work as a doula is built on Responsibility, Sustainability, Curiosity, and Inclusivity. That means being curious enough to question institutional narratives when they don't hold up, and giving you the evidence and confidence to make decisions based on your instincts, not institutional fear.
If you’ve been told your baby is measuring 'too small', 'too big', or somewhere in between, and you feel like you’re being pushed down a path you're not sure about, we can talk.
Book a free discovery call with me here, we can look at the evidence together, so you can make a decision with your whole heart that's right for you.
Further reading and resources
If you’ve been told your baby is "measuring big" and you're not hearing a balanced take from your maternity care professionals, these are the exact resources I recommend to my clients:
Dr Sara Wickham
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Book: In Your Own Time: — Evidence-based information about induction of labour, informed decision-making, and why waiting for spontaneous labour is often safer than many people realise — or have been told.
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Articles & Analysis: Visit sarawickham.com for her extensive catalogue of articles relating to Big babies and/or induction.
Dr Rachel Reed
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Book: Why Induction Matters — Options related to inducing labour or choosing to wait are explored, and women’s experiences are included throughout. The book aims to help parents make their own informed decisions about induction of labour.
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Blog: MidwifeThinking.com — Rachel’s archive includes deep dives into shoulder dystocia, the mechanics of physiological birth, and why female pelvises are inherently built to birth human babies.
The Great Birth Rebellion Podcast (Melanie Jackson)
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Type in "Big Babies" into the Search field - there are plenty of episodes to choose from