35 Weeks Pregnant: The Secret Purpose of All That Baby Fat

Last week, your baby was rehearsing for their very first feed. This week, they turn their energy to filling out, plumping into the soft, round newborn you are about to meet. And that gorgeous baby fat is doing far more than you might think.

Welcome to week thirty-five. Your baby is getting chubby with real purpose, their brain is in a huge growth spurt, and they are running low on room in there. Let me show you.

Your baby is filling out, for a reason

This week, your baby pours their energy into one main job. Getting deliciously, gloriously chubby.

The fat your baby has been gathering for weeks now goes on faster than ever, plumping out their arms and legs, rounding their cheeks, smoothing every last wrinkle until they look like the soft little newborn they are about to be. But here is what most people do not realise. This fat is not just for cuddles. It is essential.

That layer of fat is what will keep your baby warm in the cold, bright world outside, where they cannot yet hold their own heat the way you do. Ever since week thirty, they have been learning to manage their own warmth, and this fat is the final piece of it. It is also a precious energy reserve, a little built-in store to carry them gently through their first days, and fuel for that fast-growing brain.

So every gram of that gorgeous squish is doing a job. The cheeks you will kiss, the thighs you will marvel at, the soft round tummy, all being made now, every bit of it on purpose.

A brain growing faster than ever

At the same time, deep inside, your baby's brain is in one of the biggest growth spurts of the entire pregnancy.

It is getting visibly bigger and more wrinkled, adding new folds and forming connections at a tremendous rate. An enormous amount of this brain growth happens in these final weeks, which is part of why every single week now, tucked up safe inside you, is so precious for your baby. They are using this time beautifully, growing the very mind they will meet the world with.

Running out of room

With your baby this big, the roomy world they once somersaulted through has become rather snug.

There simply is not the space for those big, swooping movements anymore. Instead, you will feel squirms, wriggles, stretches, and the firm press of a heel or an elbow as your baby shifts about. This is completely normal, and your baby should still be moving regularly every single day, right up until birth. A busy baby is a reassuring baby.

How big is my baby at 35 weeks?

Around forty-six centimetres now, head to heel, and roughly two and a half kilograms. Your baby is round, smooth, and soft, with chubby cheeks and very little wrinkle left to them, looking very much like the baby you will hold in just a few weeks.

Plump, cosy, and almost ready for your arms.

What is happening in my body?

You are nearly there now, with just a handful of weeks to go.

Your bump is at its biggest and heaviest, and you may feel slow, breathless, and quite ready to be done, which is completely understandable. Some mothers, especially first-timers, notice their baby 'drop' lower into the pelvis around now, which can ease the pressure on your lungs and make breathing easier, while adding a new heaviness down low and, often, even more trips to the loo. Rest as much as you possibly can, listen to your body, and keep checking in with your midwife. The finish line really is in sight.

From Courtney. I have spent years caring for the tiniest babies, the ones who arrived before they had the chance to lay down this soft padding, and it taught me to see baby fat completely differently. Those gorgeous rolls and round cheeks your baby is growing right now are not just for the camera. Every gram is keeping them warm, fuelling that hungry brain, and holding a little reserve of energy to see them safely through their very first days. So when you finally meet your baby and sink into those impossibly soft cheeks, know that every bit of that squish was made on purpose, in these very weeks, by you. Nature does not waste a thing. And neither, mama, does a mother's body.

The one thing to do this week

This week, make a gentle daily habit of tuning in to your baby's movements. Not anxiously, and not by the clock, just a quiet few minutes, perhaps in the evening when babies are often liveliest, with your hand on your bump, feeling them shift and stretch and say hello.

It is reassuring, it is one of the loveliest ways to bond before birth, and it helps you stay tuned in to what is normal for your baby. You know them best now. If their usual pattern ever changes, never hesitate to call your midwife, day or night. And if you would like a simple way to keep an eye on it, the free kick tracker in the Mama Years app is always there to help you feel sure.

Then, feet up. You and that busy little person have both earned the rest.

Coming up in week thirty-six

Next week, your baby settles lower and deeper into position, getting into the starting blocks for birth, with most babies now snugly head-down and ready. Their tiny toenails finish growing right to the tips of their toes, and they keep softening and rounding, just waiting for the day.

Week thirty-six is where the countdown truly begins. I will see you there.

Written by Courtney Garland, NICU nurse, lactation consultant and mother of four, and founder of The Mama Years. This is here to inform and reassure you. It is not a substitute for medical advice, so always follow the guidance of your own doctor or midwife.

The Mama Years. 2026.

References

American College of Obstetricians and Gynecologists. (n.d.). How your fetus grows during pregnancy. https://www.acog.org/womens-health/faqs/how-your-fetus-grows-during-pregnancy

Cleveland Clinic. (2023). Fetal development: Stages of growth. https://my.clevelandclinic.org/health/articles/7247-fetal-development-stages-of-growth

Mayo Clinic. (2025). Fetal development: The third trimester. https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/fetal-development/art-20045997

Merck Manual. (2024). Stages of fetal development (Consumer Version). https://www.merckmanuals.com/home/women-s-health-issues/normal-pregnancy/stages-of-fetal-development

The Mama Years is written by Courtney Garland, a NICU registered nurse and IBCLC lactation consultant, against the research. When the science is genuinely unsettled, she says so instead of guessing. Nothing here replaces the advice of the clinician looking after you.