The third trimester is the final stretch, from about 28 weeks until your baby is born. Australia's Pregnancy, Birth and Baby says a baby born between 37 and 42 weeks is full term, and that the trimester ends whenever your baby arrives. Check-ups become more frequent, and the focus shifts to your baby's movements and growth, your blood pressure, and getting ready for the birth.
Three habits matter most now. Get to know your baby's pattern of movements, and call your maternity unit straight away if it changes. Go to sleep on your side from 28 weeks. And know the signs that mean calling now rather than waiting for your next appointment: they're listed under "When to get help" below.
When is the third trimester?
The NHS week 28 page welcomes you to the third trimester at 28 weeks. Pregnancy, Birth and Baby counts it from week 27. Either way, it ends with the birth, and Pregnancy, Birth and Baby says babies born before 37 weeks are premature.
| Weeks | What usually happens |
|---|---|
| 28 | Side-sleeping starts; RSV vaccine (Australia, UK); blood tests |
| 28 to 36 | Check-ups every 2 to 4 weeks |
| 35 to 37 | Group B strep swab (many Australian services) |
| 36 | Baby's position checked |
| 37 | Full term |
| 40 | Due date |
| 41 | Induction offered (UK); extra monitoring |
| 42 | Overdue (Australia) |
Common changes include heartburn, backache, swelling of the ankles, feet and face, and trouble sleeping, says the NHS. Pregnancy, Birth and Baby adds shortness of breath, tiring easily, and Braxton Hicks tightenings that last around 30 seconds and aren't labour. If this is your first baby, it says your baby may move lower into your pelvis around 36 weeks, which can ease your breathing but means more trips to the toilet.
How should my baby's movements feel now?
Healthy babies don't move less towards the end of pregnancy. Pregnancy, Birth and Baby's movements page says you should keep feeling your baby move right up until birth and even during labour. The RCOG's leaflet on movements says the number of movements tends to increase until 32 weeks and then stay about the same. The kind of movement you feel can change as your baby grows, but less movement isn't something to put down to running out of room.
There's no set number of kicks to reach. The NHS page on your baby's movements says to get to know your baby's usual pattern and to contact your midwife or maternity unit straight away if your baby is moving less than usual, you can't feel movements, or the pattern has changed: "Do not wait until the next day – call immediately, even if it's the middle of the night." Don't use a home doppler to check.
When you go in, the RCOG says your baby's heart rate will usually be monitored for at least 20 minutes. An ultrasound scan may be arranged, for example if your womb is measuring smaller than expected, and is normally done within 24 hours. If movements slow again later, call again every time. Our guide to baby movements in pregnancy has more.
Why go to sleep on your side from 28 weeks?
The NHS sleep and tiredness page says research suggests that after 28 weeks, falling asleep on your back can double the risk of stillbirth. Safer Baby in Australia says going to sleep on your side after 28 weeks can halve the risk compared with going to sleep on your back.
- Either side is fine. Both sources say left or right.
- Start every sleep on your side, including daytime naps and going back to sleep in the night.
- Don't worry if you wake on your back. Just roll onto your side and go back to sleep.
For why it matters and how to get comfortable, see sleep positions in pregnancy.
What happens at antenatal appointments now?
Appointments become more frequent. Pregnancy, Birth and Baby says about every 4 weeks until 36 weeks, then every 2 weeks. The NHS antenatal appointments page lists appointments at 28, 34, 36, 38 and 40 weeks, plus 31 weeks for a first baby and 41 weeks if you're still pregnant.
At most visits, your midwife or doctor will:
- check your blood pressure and urine, looking for signs of pre-eclampsia
- measure your bump to check your baby's growth
- ask about your baby's movements and your mental health
- feel your bump to check your baby's position, from about 36 weeks.
Pregnancy, Birth and Baby's checkups chart adds a blood count at 28 weeks, an anti-D injection if you're Rh negative, and an ultrasound to check the fluid around your baby at 41 weeks.
Pregnancy, Birth and Baby says about 1 in 25 babies are breech (bottom-first) when labour begins. If your baby isn't head-down at 36 weeks, the NHS week 36 page says you may be offered ECV, where a doctor or midwife gently presses on your bump to help your baby turn, and that it works around half the time.
Will I be tested for group B strep?
Group B strep (GBS) is a common bacterium that usually causes no symptoms in adults, but can rarely make a newborn seriously ill. Testing differs by country.
| Region | Testing | Timing |
|---|---|---|
| Australia | No national standard; many services swab everyone | 35 to 37 weeks |
| UK | Not routine on the NHS | Ask your midwife if it applies to you |
| US | Everyone screened | 36 to 38 weeks |
- Australia. Pregnancy, Birth and Baby's GBS page says there's no standard practice: many providers offer every pregnant person a swab of the vagina and rectum at 35 to 37 weeks, which you can usually take yourself, while others give antibiotics in labour only if you have risk factors. It says about 1 in 5 females carry GBS, and testing is your choice.
- UK. The NHS group B strep page says routine testing isn't recommended. You may be advised to have antibiotics through a drip in labour if GBS was found in this pregnancy or a previous baby was affected.
- US. ACOG says GBS screening is part of routine care, with a swab between 36 and 38 weeks, and that about 1 in 4 pregnant women carry it.
If you carry GBS, antibiotics in labour lower the chance of your baby getting an early infection. Pregnancy, Birth and Baby says they don't prevent late-onset infection, so know the signs after birth. The NHS says to call 999 if your baby is floppy or not responding normally, grunting or working hard to breathe, breathing very fast or slowly, has blotchy skin or a change in colour, or has an unusually high or low temperature. See when to call a doctor for other newborn warning signs.
What are the signs of pre-eclampsia?
Pre-eclampsia is a serious condition that raises your blood pressure and can affect your kidneys, liver and brain. Pregnancy, Birth and Baby's pre-eclampsia page says most women don't notice symptoms, which is why your blood pressure is checked at every visit. The NHS pre-eclampsia page lists these signs:
- a severe headache that doesn't go away with simple painkillers
- vision problems, such as blurring or flashing lights
- pain just below the ribs
- sudden swelling of your face, hands or feet
- heartburn that doesn't go away with medicine, being sick, or feeling very unwell.
If you have any of these, call your maternity unit straight away. The NHS week 28 page warns that blood pressure can rise "dangerously high, very quickly", even if you feel well, so get any new swelling checked. The NHS adds that pre-eclampsia can also develop in the days or weeks after birth.
How do I get ready for the birth?
Pregnancy, Birth and Baby suggests these jobs for the third trimester:
- Go to antenatal classes.
- Pack your hospital bag. The NHS week 36 page says to make sure it's packed, with your hospital number and key phone numbers easy to find. See our hospital bag checklist.
- Book a tour of the hospital or birth centre.
- Get a properly fitted car seat to bring your baby home. See car seat safety.
- Arrange care for other children or pets while you're in hospital.
- Stock up on staples, and cook extra meals for the freezer.
Write down your preferences for labour and birth while you have time to think: our birth plan guide walks you through it. And learn how labour starts, how to tell real contractions from Braxton Hicks, and when to call, in signs of labour. Pregnancy, Birth and Baby says to call your hospital, midwife or doctor if you think labour has started.
What happens if I go past my due date?
A due date is an estimate, and many babies arrive after it. Here's how each country handles it.
- UK. The NHS induction page says induction will be offered if labour hasn't started naturally by 41 weeks, and a membrane sweep is usually offered after 39 weeks. If you decide not to be induced and your pregnancy goes beyond 42 weeks, it says you should be offered increased monitoring of your baby.
- Australia. Pregnancy, Birth and Baby's overdue page says you're overdue if labour hasn't started by 42 weeks, and the risk of stillbirth rises the longer you go overdue, though it's still low. Checks may include an ultrasound and monitoring of your baby's heartbeat (CTG), perhaps 2 times a week. Its induction page lists being overdue (41 to 42 weeks) as a reason induction may be recommended.
- US. ACOG calls 41 to 42 weeks "late term", says testing may be recommended from 41 weeks, and says induction may be recommended at 41 weeks.
Induction may involve opening the cervix with a balloon catheter, breaking your waters, medicines to start contractions, or a combination. Pregnancy, Birth and Baby says an induced labour can build faster and feel more intense, and that it can take a few hours or more than 24 hours until your baby is born. It's your choice, so ask about the reasons, the risks and the alternatives.
How are you feeling?
Late pregnancy can bring worry about the birth or about becoming a parent, and poor sleep makes everything harder. Pregnancy, Birth and Baby says 1 in 5 people will experience antenatal anxiety or depression, and to seek help early if you or your partner feel this way. The NHS mental health in pregnancy page says some people get depression or anxiety for the first time in pregnancy, and encourages you to be honest with your midwife or GP.
Talk to your midwife, GP or obstetrician about how you're feeling. You can also contact Samaritans on 116 123. If you have thoughts of harming yourself or your baby, call Samaritans on 116 123 or 999 now. See postnatal mood for what can happen after the birth, too.
When to get help
These follow the NHS bleeding in pregnancy page, which says to call an ambulance if you're bleeding and have severe tummy pain, feel faint or dizzy, or the bleeding is heavy. For other labour emergencies, such as seeing or feeling the cord, see signs of labour.
Call your maternity unit, birth suite or midwife now, day or night, if you:
- feel your baby moving less, can't feel movements, or the pattern has changed
- have any vaginal bleeding
- have a gush or trickle of fluid, or think your waters have broken
- have regular, painful contractions or tightenings before 37 weeks
- have signs of pre-eclampsia (listed above)
- have itchy palms or soles, or itching that's worse at night
- have a fever, or severe nausea and vomiting.
The itching advice comes from the NHS page on itching in pregnancy, which says it could be a sign of intrahepatic cholestasis of pregnancy, which needs urgent treatment. The rest follows Pregnancy, Birth and Baby's third trimester page, which says to contact your midwife, doctor or hospital immediately. In the US, the CDC's urgent maternal warning signs also include a baby's movement stopping or slowing, a headache that won't go away, changes in vision, and severe swelling, redness or pain in a leg or arm, and say to seek medical care immediately. The CDC list also includes chest pain and trouble breathing, which is why they're in the emergency list above. If you can't get through to your unit, go to your hospital.
What's useful to note down?
Jot down when your baby is usually busy and what the movements feel like, so a change stands out. Keep your hospital number, your GBS result and your blood group with your notes or in your bag. If you call about movements, have the time you last felt your baby move ready. Never wait to finish notes before calling.