The brain continues its extraordinary folding. The fat continues accumulating — the baby has reached 1.5kg, gaining approximately 200–250g per week from now until birth. And this week brings two parallel biological systems, operating simultaneously, both directed at the same purpose: equipping your baby to survive in the world they are about to enter.
This is why the timing of vaccines in pregnancy matters: the whooping cough vaccine offered from week 16 specifically targets this transfer window. The antibodies you produce in response to the vaccine cross the placenta and equip your baby with protection they cannot yet generate themselves. Vaccination in pregnancy is not just protection for the parent — it is direct immune transfer to the newborn.
The baby is also continuing the reflexes and sensory development of recent weeks. The sucking reflex — practised since week 13 — is now well established. The grip reflex is strong enough that if a finger were placed in the baby's palm, they would close their fist around it with measurable force. The eyes are opening and closing regularly. The breathing motions are rhythmic and consistent. The baby at 31 weeks is, in almost every structural and functional sense, a complete human being — smaller and less mature than at birth, but complete.
My midwife explained the antibody transfer at the thirty-one week appointment and I found it genuinely moving — this idea that my immune history was being handed over, like a gift I hadn't known I was making. Every infection I'd fought, every vaccine I'd had — some version of that protection was going to them. It felt like the most intimate thing I could give anyone.
Simultaneously with the placental antibody transfer, the breast tissue is producing colostrum — the first milk — which some people begin to notice leaking from the nipples from around weeks 28–32. Its appearance is startling to many people who haven't been told to expect it: thick, yellowish, sometimes amber or clear, in tiny amounts.
What it contains: high concentrations of secretory immunoglobulin A (sIgA) — an antibody that coats the lining of the baby's gut, protecting it from pathogens before the immune system is fully functional. Also: white blood cells, growth factors, lactoferrin (antibacterial), and a natural laxative that helps clear meconium (the first bowel movement).
Why the volume is small: a newborn's stomach is the size of a cherry and holds around 5–7ml. The small volume of colostrum is precisely calibrated to what a healthy newborn needs — it is not a sign of inadequate supply. Mature milk typically comes in between days 3 and 5 after birth.
Colostrum harvesting: some people are advised to hand-express and freeze colostrum from around 36–37 weeks as a supplement for the immediate postnatal period. This is recommended for those at higher risk of feeding difficulties (people with diabetes, people planning a caesarean, those who have had previous breast surgery). Ask your midwife whether harvesting is appropriate for you — do not start before 36 weeks without this conversation, as nipple stimulation can occasionally trigger contractions in susceptible individuals.
I noticed colostrum leaking at thirty-one weeks and completely panicked — I thought something was wrong. My midwife was wonderfully matter-of-fact: "Your body is preparing to feed your baby. It's been preparing for months. This is the visible bit." I found that reassurance enormously calming. It wasn't going wrong. It was going exactly right.
The 31-week appointment happens this week. Beyond the routine checks, it is a useful opportunity to review progress on preparation and raise any symptoms that have accumulated since the 28-week check. The frequency of appointments increases from here — fortnightly from this point until 36 weeks, then weekly — reflecting the increased monitoring appropriate to the final trimester.
What helps: reducing fluid intake in the two hours before bed (while staying fully hydrated through the day); a gentle pelvic tilt before sleep can sometimes shift the baby's position slightly; ensuring the bladder is as fully emptied as possible by leaning slightly forward when urinating. None of these are complete solutions — they reduce disruption rather than eliminating it. Expecting broken nights from now is realistic planning.
Week 31 has a particular emotional quality that is specific to the third trimester: a growing sense of the extraordinary nature of what is happening simultaneously in the body. Antibodies being transferred. Colostrum forming. A brain completing its folding. A person almost ready. Nine weeks. The physical discomforts are real and the preparation urgency is genuine, but so is the wonder of what is actually happening.
The colostrum detail — the first milk already present, the body preparing to nourish a baby who has not yet arrived — tends to shift something in how people think about the pregnancy. It is not just growing a baby; it is preparing to sustain one. The body is doing both at once, simultaneously, without being asked. That is worth pausing for.
Thirty-one weeks was when I started to feel genuinely impatient. Not anxious-impatient — excited-impatient. I'd been in the pregnancy for so long, thinking about them for so long, that I found myself wanting to skip to the part where I could see their face. The antibody transfer story was the thing that tipped me over into it. This unseen generosity, already happening. I just wanted to meet them.
The preparation list continues. Nine weeks contains everything that remains to be done — and, for most people who are on track, not as much as it might feel like. The things that are already done are real. The things that remain can be done. The birth is coming, and it is coming to someone who has been building toward it for thirty-one weeks.
Week 31 connects to these guides — both the feeding one and the birth one are urgent reading now.
The colostrum and antibody transfer story this week is a useful thing to understand as a partner — not just because it is remarkable, but because it reframes the physical demands of this stage. Your partner's body is not just sustaining a pregnancy; it is simultaneously building and loading two separate biological systems for the life that follows the pregnancy. The tiredness and physical challenge of weeks 30–36 are not just the weight of the bump — they are the cost of this extraordinary parallel effort.
Understanding this changes how the support looks. Not "you're tired, rest more" but "your body is doing something it has never been asked to do before, and it is doing it well." Acknowledgement of what is actually happening, rather than management of the symptoms, is the more useful form of support at this stage.
- Read the breastfeeding guide. Whether or not your partner plans to breastfeed, understanding what colostrum is, how the milk comes in, what the early feeding challenges are, and how you can support them — as a physically present, practically helpful person in the room — is some of the most useful preparation you can do. The early days of feeding are often when support makes the most difference.
- The 31-week appointment. Attend if possible. It includes fundal height, foetal position, blood pressure, and a chance to review preparation progress. The next one is at 34 weeks — the pace is increasing.
- Hospital bag check. Where is it? What's in it? What's still missing? Is the car seat fitted? Is there a working plan for the day labour starts, including who does what if it happens at an inconvenient time?
Read the WiseMama breastfeeding guide — whether or not you plan to breastfeed. The first hours after birth, whatever your feeding intention, are likely to involve colostrum. Understanding what it is, why the volume is small, and why that is appropriate rather than a problem means you will not be alarmed or misled by well-meaning people suggesting you "top up" in the first 24 hours when the colostrum is doing exactly what it needs to do.
At today's appointment, raise two things:
This opens a conversation about feeding intention and any risk factors that might make early harvesting advisable. Most people do not need to harvest before 36–37 weeks, but knowing your individual situation in advance of that window allows for a planned rather than reactive approach to it. The second question worth raising is the foetal position — as at week 30, ongoing awareness of where the baby is lying helps both of you prepare for the final weeks.