31 Weeks Pregnant: The Wiring of a Whole Mind

Last week, your baby began taking over the running of their own body. This week, deep in that busy head, the wiring of a whole mind is being laid, connection by connection, at a furious pace.

Welcome to week thirty-one. Your baby's brain is linking itself together faster than at almost any other time of their life, their eyes are learning to handle light, and that little person is nearly fully formed. Let me show you.

Your baby's brain is wiring itself together

You may remember that, very early on, your baby's brain grew its billions of cells at a dizzying pace. Those cells have been there for months now. But a brain is not just cells. It is connections. And this week, those connections are forming faster than at almost any other time in your baby's whole life.

Picture each brain cell reaching out and linking hands with thousands of others, building a vast, intricate web. Trillions of these connections will form over these final weeks and the months after birth, and they are the actual wiring of your baby's mind, the pathways that will one day carry every thought, every memory, every feeling, every word.

And here is the part I love most. These connections are shaped by experience. Every sound your baby hears, every taste and touch, every bit of your voice and the rhythm of your days, helps lay them down and strengthen them. You do not need flashcards or clever programmes or anything special at all. Just by living your ordinary life with your baby tucked along for the ride, you are helping to wire their brain, this week and every week. The two of you are building a mind together.

Eyes that react to the light

A small, lovely change is happening in your baby's eyes this week too.

The pupils, the dark centres of the eyes, can now widen and narrow in response to light, exactly as yours do. Shine a bright light and they will shrink, dim it and they will open up to let more in. It is one of the last fine adjustments before those eyes are ready to meet the dazzling brightness of the world, and your face in it.

How big is my baby at 31 weeks?

Around forty-one centimetres now, head to heel, and roughly one and a half kilograms. Your baby is laying down fat fast, looking rounder and softer by the week, and filling almost all the space inside you, which is why every stretch and kick is so easy to feel.

Nearly fully formed now, and mostly just growing, plumping, and getting ready for you.

What is happening in my body?

As you move through these final weeks, you may start to feel a shift, from being pregnant to getting ready to actually meet your baby.

Physically, this stretch can be demanding. Your bump is large, sleep is elusive, and you may feel breathless or achy or simply done in by the end of the day. You might also notice a sudden burst of energy and the urge to clean, sort, and organise, the famous nesting instinct. Follow it if it comes, but gently, and never at the cost of resting. Listen to your body, lean on your people, and keep checking in with your midwife.

From Courtney. I love that this is the week the wiring really gets going, because of what actually does the wiring. Not flashcards. Not fancy programmes. You. The sound of your voice reading out a shopping list. The rhythm of your footsteps. Your laugh, your music, the steady beat of your heart. All of it, the perfectly ordinary stuff of your days, is helping to lay down the connections in your baby's brain. So if you ever feel like you should be doing more to prepare this little person for the world, please hear me. You already are, simply by carrying them through your life. You are more than enough, exactly as you are, mama. You always have been.

The one thing to do this week

This week, as you head deeper into the final stretch, you might notice the urge to start getting ready creeping in. That instinct is worth leaning into, gently and at your own pace.

If you would like a hand knowing where to begin, I have put together a Prep for Baby course inside the Mama Years app that walks you through it all, the checklists and the hospital bag, what to expect with feeding and recovery, and those tricky first nights of newborn sleep, so you can feel calm and ready rather than overwhelmed. It is there for whenever you want it, with no rush at all.

And remember, there is no pressure. Resting and daydreaming about your baby is preparation too. Put those feet up whenever you need to.

Coming up in week thirty-two

Next week, your baby starts getting into position for the big day, with many babies beginning to settle head-down, ready for birth. Their practice breathing grows stronger, their tiny fingernails reach the very tips of their fingers, and they keep busily filling out.

Week thirty-two is where your baby starts getting ready for the journey out. 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.