Last week's surfactant story — the lungs beginning to produce the substance that makes breathing possible — continues this week with a new, linked development: the nostrils have opened. For the first time, the nasal passages are unblocked and the baby is inhaling amniotic fluid through both nose and mouth in practised, rhythmic movements. This is the breathing rehearsal that will prepare the lungs and respiratory muscles for the moment, still fifteen weeks away, when they must take their first breath of actual air.
The senses continue to sharpen. The nostrils opening also means the sense of smell is beginning its development — the baby will be able to detect certain compounds dissolved in the amniotic fluid, continuing the flavour and scent education that has been underway since taste receptors activated at week 19. Research suggests that newborns can recognise the smell of the amniotic fluid they spent months in — another thread of familiarity connecting the womb to the outside world.
The baby has reached 222mm and 660g, gaining roughly 60g in a week. The fat layer is accumulating, the skin is gradually becoming less translucent, and the face continues to fill out slightly. The eyes, which were preparing to open last week, continue on that trajectory — they will unsealed and begin opening and closing at around week 26.
I found out about the breathing practice at a late antenatal appointment and couldn't stop thinking about the diligence of it. This tiny, constant rehearsal, already underway. I started becoming much more aware of my own breathing when I thought about it — the completely ordinary thing I did forty thousand times a day, already being practised in the dark by someone learning to exist.
The uterus has reached roughly the size of a football this week — large enough to be felt clearly above the navel, large enough to be pushing significantly against the diaphragm, stomach, and other abdominal organs. Shortness of breath on exertion, heartburn, and a sense of pressure beneath the ribs are all increasingly common as a direct result of this upward displacement. These symptoms will intensify over the coming weeks and typically ease slightly in the final weeks of pregnancy when the baby descends into the pelvis (called 'lightening' or 'engagement').
Symptoms to watch for: unusual fatigue (beyond normal pregnancy tiredness), breathlessness that seems disproportionate to exertion, pallor, palpitations, dizziness, difficulty concentrating, headaches, and a craving for non-food substances like ice or soil (pica — a specific sign of iron deficiency).
When it's checked: blood tests at the booking appointment and at 28 weeks check haemoglobin and iron levels routinely. If you have symptoms before 28 weeks, ask your midwife to check sooner.
What to do: if iron deficiency anaemia is confirmed, prescribed iron supplements are far more effective than dietary changes alone — though diet matters too. Iron is best absorbed on an empty stomach, with vitamin C, and away from tea, coffee, and calcium (which inhibit absorption). The supplements can cause constipation; increasing fibre and fluid intake helps. Most people see improvement in iron levels within 4–6 weeks of supplementation.
Non-haem iron (less absorbable but valuable): lentils, beans, chickpeas, tofu, fortified breakfast cereals, dark leafy greens (spinach, kale), dried apricots, pumpkin seeds, and quinoa.
Absorption boosters: eat vitamin C alongside non-haem iron sources — a glass of orange juice with lentil soup, tomatoes with chickpeas, peppers with leafy greens.
Absorption blockers to be aware of: tea and coffee contain tannins that significantly reduce iron absorption — avoid drinking them within an hour of iron-rich meals or supplements.
Week 25 sits in a curious position in the arc of pregnancy: it has the quality of late second trimester — relatively comfortable, the movements well established, the major milestones of viability and the halfway point recently passed — but it carries the beginning awareness that the third trimester is now only two weeks away. The pace of the second half of pregnancy is noticeably faster than the first, and that acceleration is starting to be felt.
For many people, week 25 is when the practical reality of preparation begins to feel genuinely pressing rather than comfortably abstract. There are fifteen weeks until the due date. Antenatal classes need to be attended, not just booked. Birth preferences need to be thought through, not just intended. Nursery, equipment, maternity leave arrangements — if these conversations haven't happened yet, this is the week to begin them with urgency rather than good intention.
I hit twenty-five weeks and suddenly had a very clear sense that time was moving faster than I'd reckoned. I'd been so focused on the milestones — twelve weeks, twenty weeks, twenty-four weeks — that I hadn't really thought about the weeks between them as passing. Then I looked up and found I had fifteen weeks left and hadn't sorted the nursery, hadn't bought anything, hadn't started classes. It was fine — there was still time. But it was a useful alarm.
The physical changes of the body are also becoming harder to ignore at this stage. The bump is substantial. Moving, sleeping, and sitting comfortably all require more management than they did two months ago. For most people this is simply a feature of late pregnancy to be accepted and worked around — but it is worth noticing when physical discomfort is crossing from manageable into significantly affecting quality of life, and seeking support when it does.
The themes of week 25 connect to these full topic guides.
Two weeks until the third trimester. The preparation that has been easy to defer — because there has always been time — is now on a real timeline. This is the week for concrete action on anything that has been 'on the list': antenatal classes actually attended (not just booked), nursery furniture ordered rather than browsed, maternity and paternity leave formally notified to employers rather than mentally planned.
The physical demands on your partner are increasing week by week. The football-sized uterus makes sleeping, bending, walking, and breathing more effortful than they were a month ago. Noticing this without waiting to be told about it — adjusting your pace on walks, taking on the physical tasks that have become harder, making the sleeping environment as good as it can be — is the most consistently useful thing partners can do at this stage.
- Ask about iron. Anaemia is common now and makes everything harder — the fatigue of low iron on top of pregnancy fatigue is significant. If your partner seems more tired than usual or is breathless doing things that shouldn't cause breathlessness, encourage them to mention it at the next appointment.
- Begin reading about newborn care. The WiseMama newborn topic, safe sleep, and feeding guides are worth both of you reading now — before the exhaustion of the postnatal period makes absorbing new information much harder. Knowledge acquired now is available when it's needed.
- Plan your paternity / partner leave properly. Not just when you will take it, but what it will actually look like — what your partner needs from you in those first weeks, what a good early postnatal period looks like practically, what you need to have in place before then.
Ask your midwife to check your iron levels if you haven't had a blood test since the booking appointment. Routine iron testing is offered at 28 weeks, but if you are symptomatic — unusually fatigued, breathless, dizzy, or experiencing pica (cravings for ice, soil, or non-food substances) — it is worth asking for an earlier check. Iron deficiency anaemia is both common and very treatable, and identifying and supplementing it earlier produces a significantly better experience in the third trimester and at birth.
At your next appointment — and especially if symptoms suggest it:
This is also a good appointment to raise the 28-week blood tests as a topic — what they include, what they check for, and what the results will cover. The 28-week appointment includes a full blood count and often the glucose tolerance test result if you've had one. Understanding what is coming means you arrive at that appointment as an informed participant rather than a passive recipient.