The third trimester: what to expect from weeks 28 to 40

Pregnancy · Updated July 2026 · All articles

The third trimester is the final stretch: from week 28 until your baby arrives. Your body is working incredibly hard, your baby is growing fast, and antenatal appointments become more frequent to make sure everything is on track. This trimester brings the most intense physical changes of pregnancy, the most important safety checks, and the preparations that mean you are ready for birth whenever it begins. Here is what to expect.

When the third trimester starts

The third trimester begins at week 28 and continues until birth. Most pregnancies reach their due date around week 40, but a full-term birth can happen anywhere between weeks 37 and 42. If your pregnancy continues past 41 or 42 weeks, your midwife will discuss induction of labour as the risk of complications increases significantly after 42 weeks. Babies born before 37 weeks are considered premature and will receive specialist neonatal care.

From 28 weeks, antenatal appointments usually become more frequent. In a straightforward first pregnancy on the NHS you will have appointments at 28, 31, 34, 36, 38, 40 and 41 weeks. Additional appointments are added if there are any concerns or if you are in a higher-risk category. These later appointments include blood pressure and urine checks, measurement of the fundal height (a tape measure check of the uterus size), and discussions about your birth plan and preparation.

Physical changes in the third trimester

The third trimester brings a wave of physical changes as the baby grows rapidly and your body adjusts to accommodate it.

Breathlessness and rib pain: as the uterus pushes upward against the diaphragm, many people find they become breathless on minimal exertion. This is normal and not dangerous, though it can be uncomfortable. Rib pain and a feeling of pressure beneath the ribs is also common. At around 36 weeks, when many babies move head-down and engage in the pelvis, the pressure on the diaphragm often eases considerably, a shift sometimes called "lightening."

Pelvic pressure and pelvic girdle pain: as the baby descends and hormones loosen the ligaments around the pelvis in preparation for birth, many people experience significant pelvic pressure. Pelvic girdle pain (PGP) is a distinct condition affecting around one in five pregnancies. If you have pain in your pubic area, lower back or hips that worsens with walking, climbing stairs or turning over in bed, ask your midwife for a physiotherapy referral.

Swelling: oedema (swelling) of the feet and ankles is very common in the third trimester. It tends to be worse at the end of the day and in warm weather. Gentle elevation of the feet, compression socks and staying mobile all help. Sudden severe swelling, especially if it affects the face or hands, or if it is accompanied by headache, should be reported to your midwife urgently as it can indicate pre-eclampsia.

Tiredness and sleep disruption: sleep often becomes more difficult in the third trimester due to the size of the bump, the need to turn frequently, and increased urination. Sleeping on your side (either side) from 28 weeks is recommended. Research has shown an association between sleeping on your back in the third trimester and an increased risk of stillbirth, though the risk is small. If you wake up on your back, simply roll onto your side.

Braxton Hicks contractions

Braxton Hicks contractions are the uterus's way of practising for labour. They are irregular, usually painless or mildly uncomfortable tightenings of the abdomen, and they have no predictable pattern. They are very common from around 28 weeks onwards and tend to become more frequent as you approach your due date. Drinking a glass of water, changing position or having a bath often causes them to ease or stop.

The key distinction between Braxton Hicks and early labour contractions is pattern. Braxton Hicks are irregular, do not become more frequent or intense over time, and usually ease with rest. True labour contractions become longer, stronger and closer together over a period of hours. If you are unsure which you are experiencing, timing the contractions over an hour is a useful starting point. If they are irregular and not intensifying, they are most likely Braxton Hicks.

Growth scans and Group B Strep screening

Some pregnancies require additional growth scans in the third trimester to check that the baby is growing at the expected rate. These are offered if you have a higher risk of growth restriction, if fundal height measurements are smaller than expected, or if you had complications earlier in pregnancy. The NHS does not offer routine growth scans to all low-risk pregnancies, but they are widely available privately.

Group B Streptococcus (GBS) screening is not offered routinely by the NHS to all pregnant people, but it is available privately from around 35 to 37 weeks. GBS is a bacterium carried by around 25 to 30 percent of people without causing illness. In most cases it poses no risk, but certain factors in labour (preterm birth, prolonged membrane rupture, fever in labour) increase the risk of the bacteria passing to the baby. If you test positive for GBS, you will be offered intrapartum antibiotics during labour to significantly reduce the risk of neonatal infection.

Preparing for birth

The third trimester is the time to move from thinking about birth to actually preparing for it. There are several practical tasks worth completing before 37 weeks.

Hospital bag: pack your bag by around 36 weeks. For labour: a birth preferences document, comfortable clothes or a nightgown, snacks, a phone charger, and any items that help you feel calm (a playlist, a scented item, a photo). For after the birth: clothes for you (front-opening if you plan to breastfeed), toiletries, nappies and babygrows for the baby, and a car seat to get home. Check your hospital or birth centre's specific guidance as requirements vary.

Birth preferences: a birth preferences document (sometimes called a birth plan) is a short, clear summary of your preferences for labour, pain relief, the third stage (delivery of the placenta), skin-to-skin contact and infant feeding. It is a communication tool, not a binding contract, and its main value is prompting conversations with your midwife and ensuring your birth partner knows your priorities.

Antenatal classes: if you have not yet attended antenatal classes, the third trimester is the time. NHS-provided classes, NCT courses and independent birth preparation classes all cover labour, birth, the immediate postnatal period and infant feeding. They are also a useful way to meet other people due around the same time.

Infant first aid and car seat: a basic infant first aid course covers choking, CPR and common emergency scenarios. It takes a few hours and can make a genuine difference to confidence in those early weeks. Car seats must be fitted correctly before the birth and are legally required for driving home from hospital.

Monitoring your baby's movements

From 28 weeks, being aware of your baby's individual movement pattern is one of the most important things you can do. The RCOG and NHS do not recommend counting a specific number of kicks per day, because every baby's pattern is unique. What matters is that you know what is normal for your baby and contact your midwife or triage immediately if there is any reduction or change in their usual pattern.

Do not use a home Doppler fetal heartbeat monitor and assume everything is fine because you hear a heartbeat. A heartbeat can be present even when movements have reduced significantly. Always call your midwife or maternity triage rather than relying on a home device. They will not be bothered by you calling, and checking is always the right thing to do.

If movements have reduced, the Count the Kicks campaign advice is to contact your midwife immediately, not to wait until the next day or have a cold drink and then wait. Reduced movements can be an early sign of fetal distress and time matters.

Signs of labour versus Braxton Hicks

As your due date approaches, you may find it hard to tell whether what you are feeling is the start of labour or more Braxton Hicks. The signs that suggest real labour is beginning include: a show (a blood-tinged mucus plug coming away, which can happen days before contractions begin), a dull persistent lower backache that comes and goes, loose stools, contractions that are irregular at first but gradually become more regular, and waters breaking (which can feel like a gush or a slow trickle).

The rule of thumb that most midwives give is to call the labour ward when contractions are regular and lasting at least 45 to 60 seconds, coming every five minutes or less, and this pattern has been established for at least an hour. In a second or subsequent pregnancy, labour can progress much more quickly, so err on the side of calling earlier.

When to call maternity triage immediately

Some symptoms in the third trimester require an immediate call to your maternity triage or midwife, without waiting to see if things resolve. Do not delay if you have any of the following: reduced or absent fetal movements; any vaginal bleeding; your waters breaking, especially if the fluid is green, brown or has an unusual smell; a severe headache that does not respond to paracetamol; blurred vision, flashing lights or spots in your vision; sudden severe swelling of face, hands or feet; pain under your right ribs; or regular contractions before 37 weeks (possible preterm labour). If in doubt, always call. Maternity triage lines are there for this reason and the team would far rather reassure you than have you wait at home with a concern that needed attention.

Frequently asked questions

When does the third trimester start?

The third trimester begins at week 28 of pregnancy and continues until birth. Most pregnancies reach their due date around week 40, but a full-term birth can occur anywhere between weeks 37 and 42.

What are Braxton Hicks contractions?

Braxton Hicks contractions are irregular practice contractions that the uterus makes throughout pregnancy. In the third trimester they become more noticeable. They are usually irregular, do not increase in intensity, and ease when you change position or drink water. True labour contractions become longer, stronger and closer together over time.

When should I pack my hospital bag?

Most midwives suggest having your hospital bag ready by around 36 weeks, as babies born between 36 and 37 weeks are not uncommon. Include items for labour, for your stay after the birth, and for the baby. Your birth preferences document can go in the bag too.

How do I monitor baby movements in the third trimester?

From 28 weeks, you should be aware of your baby's individual pattern of movements. There is no set number of kicks to count per day. What matters is that you know what is normal for your baby and report any change immediately. Do not use a home Doppler and assume everything is fine if movements have reduced.

What are the signs that labour is starting?

Signs of the start of labour include a show (a blood-tinged mucus plug), lower backache that comes and goes, mild irregular contractions, and waters breaking. Regular contractions that become longer, stronger and closer together are the clearest sign that labour is progressing.

When should I call the maternity triage?

Call triage immediately if you have reduced or absent fetal movements, vaginal bleeding, your waters break (especially if coloured or smelling unusual), severe headache, visual disturbances, facial swelling, pain under your ribs, or contractions that are regular and strong before 37 weeks.

This article is for general information only. Always consult your midwife, obstetrician, or GP for advice specific to your pregnancy.