28 weeks pregnant: welcome to the third trimester
The final stretch begins, with a full check-up, a vaccine to plan and a few simple new habits.
Updated October 13, 2026 · sources checked October 13, 2026
In short
At 28 weeks the third trimester begins. The NHS says your baby is about 37.6cm from head to heel, and their heart rate has slowed to around 140 beats a minute. The one thing to do this week: go to your 28-week check and plan your vaccines (RSV from now in the UK; Tdap now in the US, RSV from 32 weeks).
Where you are at 28 weeks
The third trimester starts today, by both the ACOG and the NHS count. You are at the end of month seven in Cleveland Clinic's month grouping (weeks 25 to 28). From now on many people feel more tired and more uncomfortable, and appointments come closer together. Our pregnancy week calculator and due date calculator keep the countdown honest.
Your baby this week
The NHS measures your baby at about 37.6cm from head to heel and compares this to an aubergine (eggplant). Cleveland Clinic puts the end of month seven at about 14 to 15 inches and 2 to 3 pounds, and notes that some babies begin turning head-down around now.
Your baby's heart has been changing pace all pregnancy. The NHS describes it at around 110 beats a minute when first detectable at 5 or 6 weeks, rising to about 170 at 9 to 10 weeks, and slowing to around 140 now; it will be about 130 at birth, still far faster than your own 80 to 85.
Your body and common symptoms
- Heartburn and indigestion from your growing baby and hormones. See our heartburn guide.
- Back strain from the extra weight and looser joints.
- Puffy ankles, feet or face, especially in hot weather. Usually water retention, but the NHS asks you to get it checked in case it is pre-eclampsia, which can raise blood pressure quickly even when you feel well.
- Nosebleeds, which are common in pregnancy. The NHS advice: sit or stand (do not lie down), pinch just above the nostrils for 10 to 15 minutes, lean forward and breathe through your mouth, and put something cold at the top of your nose.
- Sleep. From today, go to sleep on your side. Pooled data from five studies linked going to sleep on the back after 28 weeks with higher odds of late stillbirth, with no difference between left and right sides (Cronin 2019).
Is this normal? When to call
Heartburn, backache, nosebleeds and tiredness are common now. Call your maternity unit or OB-GYN straight away for: your baby moving less, stopping, or changing pattern (call immediately, even at night); bleeding or fluid leaking; regular tightenings, pelvic pressure or a dull low backache before 37 weeks (ACOG preterm labor signs); a severe headache, blurred vision or flashing lights, pain below the ribs or sudden swelling; a fever of 100.4°F / 38°C or higher. UK: NHS 111 if you cannot reach your unit, 999 in an emergency. US: 911 in an emergency.
Appointments and tests around 28 weeks
| United States | United Kingdom | |
|---|---|---|
| Check-up | Prenatal visits usually move to every two weeks, then weekly near the end (Cleveland Clinic) | NHS 28-week appointment: blood test for iron levels and blood group, blood pressure, urine, bump measurement, movements, mental health, information on labour and newborn screening |
| Rhesus negative | Ask your OB-GYN about Rh immunoglobulin | NHS: injection offered if your baby is at risk of rhesus disease |
| Whooping cough | CDC: Tdap during weeks 27 to 36, earlier preferred | NHS: 16 to 32 weeks; ask now if you have not had it |
| RSV | CDC: weeks 32 to 36, September to January, or an RSV antibody for your baby after birth | NHS: from 28 weeks, all year round, every pregnancy |
| Glucose | ACOG: by 28 weeks if not done | NHS: by 28 weeks if you have risk factors |
The RSV vaccine was tested in a trial of over 7,000 pregnant women: it was 81.8% effective against medically attended severe lower respiratory tract illness in babies in their first 90 days (Kampmann 2023). The NHS says you can have it at the same time as the whooping cough and flu vaccines, but do not delay one to wait for another.
Your checklist for week 28
For your partner
The third trimester is when practical help matters most: take over the cat litter, carry the heavy shopping, and come to the 28-week appointment if you can.
Previous and next week
Week 27: side sleeping and travel · Week 29: movements and vaccines · The third trimester · All weeks
Questions parents ask
When does the third trimester start?
ACOG and the NHS both start the third trimester at 28 weeks. ACOG runs it to 40 weeks and 6 days; your baby may arrive a little before or after.
When should I get the RSV vaccine?
It depends on where you live. In the UK, the NHS offers it from 28 weeks, all year round, ideally as soon as possible. In the US, the CDC recommends it during weeks 32 to 36 from September to January; otherwise your baby can have an RSV antibody after birth, and most babies do not need both.
Do I need extra calories in the third trimester?
The NHS says you may need about 200 extra calories a day from now on, roughly two slices of wholemeal toast with margarine. There is still no need to eat for two.
Sources
- NHS — Week-by-week guide: week 28 checked October 13, 2026
- NHS — Your antenatal appointments checked October 13, 2026
- NHS — RSV vaccine checked October 13, 2026
- CDC — Vaccine Recommendations Before, During, and After Pregnancy checked October 13, 2026
- CDC — Immunizations to Protect Infants from RSV checked October 13, 2026
- Cleveland Clinic — Fetal Development: Week-by-Week Stages of Pregnancy checked October 13, 2026
- Kampmann et al. (2023), N Engl J Med — Bivalent prefusion F vaccine in pregnancy to prevent RSV illness in infants (PMID 37018474) checked October 13, 2026
- Cronin et al. (2019), EClinicalMedicine — Maternal going-to-sleep position and late stillbirth (PMID 31193832) checked October 13, 2026
Mamavela explains; it does not replace your midwife, doctor or pediatrician, who know your situation. If something worries you, call them. In an emergency, call 911 (US), 999 (UK) or 112.