27 weeks pregnant: closing the second trimester
The last week of the middle stretch, and the right moment to settle a new sleep habit before the third trimester.
Updated October 13, 2026 · sources checked October 13, 2026
In short
At 27 weeks you are in the final week of the second trimester. The NHS says your baby is about 36.6cm from head to heel and getting plumper by the day. The one thing to start this week: practise going to sleep on your side, because from 28 weeks going to sleep on your back is linked to a higher risk of stillbirth.
Where you are at 27 weeks
This is the last week of the second trimester (ACOG: 14 weeks to 27 weeks and 6 days). Next week the third trimester begins, and you will be two-thirds of the way there. In Cleveland Clinic's month grouping you are in month seven. Check your exact day with our pregnancy week calculator, or your date with the due date calculator.
Your baby this week
The NHS measures your baby at about 36.6cm from head to heel, roughly the size of a head of cauliflower. A few weeks ago their skin looked wrinkled; now fat is filling out the folds and all the organs are maturing. The NHS week 27 guide says the lungs are now capable of breathing; ACOG is more cautious, describing the lungs at 25 to 28 weeks as formed but not yet ready to work outside the uterus. Both agree that every extra week helps.
Cleveland Clinic adds that your baby can open their eyes and blink, and now has eyelashes.
Your body and common symptoms
- Bloating and constipation. Your stomach is squeezed and progesterone slows digestion. The NHS suggests plenty of water, higher-fibre choices like wholemeal bread and pasta, and lots of fruit and vegetables.
- Tiredness. Nap when you can.
- Snoring. Very common in pregnancy, the NHS says, because the nasal passages swell. It can be noisy but is not usually a concern on its own.
Going to sleep on your side
From 28 weeks, the NHS advises going to sleep on your side, at night, after waking in the night and for daytime naps. The evidence comes from studies of late stillbirth:
- A UK case-control study of 291 women who had a stillbirth after 28 weeks and 733 women with ongoing pregnancies found that going to sleep on the back the night before was linked to 2.3 times the odds of late stillbirth compared with the left side (Heazell 2018).
- A 2019 analysis pooling individual data from five studies found going to sleep on the back was linked to 2.63 times the odds, and the right side was no different from the left (Cronin 2019).
These are associations, and stillbirth remains uncommon, but the change is free and simple. The NHS tips: support your bump with a pillow, keep your knees bent, put a pillow between your legs, and if you wake on your back, simply roll back to your side. A pregnancy pillow can help some people stay comfortable; ordinary pillows work too.
Is this normal? When to call
Bloating, tiredness and snoring are normal now. Call your maternity unit or OB-GYN straight away for reduced or changed movements (the NHS says do not wait until the next day), bleeding, fluid leaking, regular tightenings or a dull low backache before 37 weeks (ACOG), or a severe headache, vision changes, pain below the ribs or sudden swelling (possible pre-eclampsia). UK: NHS 111 if you cannot reach your unit, 999 in an emergency. US: 911 in an emergency.
Appointments and tests around 27 weeks
| United States | United Kingdom | |
|---|---|---|
| Whooping cough vaccine | CDC: Tdap during weeks 27 to 36 of each pregnancy, earlier in that window preferred | NHS: from 16 to 32 weeks, usually around the 20-week scan; if you have not had it, ask now |
| Glucose screening | ACOG: 24 to 28 weeks | NHS: 24 to 28 weeks if you have risk factors |
| Next | Visits usually become more frequent in the third trimester | NHS 28-week appointment: blood tests, anti-D if needed, RSV vaccine offered |
Why it matters: after England started vaccinating pregnant women against whooping cough in 2012, the vaccine was 91% effective at protecting babies under 3 months (Amirthalingam 2014).
Your checklist for week 27
For your partner
Help build the side-sleeping nest: an extra pillow, and a gentle nudge if you notice the person you love going to sleep flat on their back.
Previous and next week
Week 26: movements and leg cramps · Week 28: welcome to the third trimester · The second trimester · All weeks
Questions parents ask
Which side should I sleep on in pregnancy?
Either side. In a 2019 analysis of five studies, going to sleep on the right side carried similar odds of late stillbirth to the left side, while going to sleep on the back was linked to higher odds. The NHS says sleeping on either side is better than on your back.
What if I wake up on my back?
Do not worry. The advice is about the position you go to sleep in, at night and for naps. If you wake on your back, just turn onto your side again.
Can I fly at 27 weeks pregnant?
The NHS week 27 guide says this is probably the last week you can fly without a fitness to fly note; after it, you may need a letter from your midwife or doctor confirming your pregnancy is uncomplicated. Cut-off dates differ, so check with your airline.
Sources
- NHS — Week-by-week guide: week 27 checked October 13, 2026
- Cleveland Clinic — Fetal Development: Week-by-Week Stages of Pregnancy checked October 13, 2026
- CDC — Vaccine Recommendations Before, During, and After Pregnancy checked October 13, 2026
- NHS — Whooping cough vaccine checked October 13, 2026
- Heazell et al. (2018), BJOG — Association between maternal sleep practices and late stillbirth (PMID 29152887) checked October 13, 2026
- Cronin et al. (2019), EClinicalMedicine — Individual participant data meta-analysis of maternal going-to-sleep position and late stillbirth (PMID 31193832) checked October 13, 2026
- Amirthalingam et al. (2014), The Lancet — Effectiveness of maternal pertussis vaccination in England (PMID 25037990) 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.