Illustration of a baby at week 28 inside the womb in cross-section, with the placenta and umbilical cord — Womb in cross-section, enlarged to show detail. Not true size.

Third trimester, week 28

28 weeks pregnant: Hello, third trimester

Size of a: Eggplant
Length: 37.6 cm head to heel
Weight: 1.2 kg WHO median
Heart rate: 110–160 bpm typical range
Due date: 84 days away 70% of the way

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Checked against the sources listed on this page. Not reviewed by a clinician. Last updated 5 November 2026. How we check.

At 28 weeks pregnant, your baby is about the size of an eggplant: roughly 37.6 cm from head to heel, weighing about 1.2 kg. You’re in your third trimester, with about 12 weeks to go until your due date.

Your baby this week

The baby can open and close their eyes and has eyelashes.
Stores of body fat are building, smoothing out the wrinkles.
REM-like sleep is appearing. Whether babies “dream” is unknown, but the brain is very busy.

Your body this week

You may be offered anti-D if you are Rh-negative, plus a repeat blood count and glucose results.
Check-ups often become more frequent: every 2 weeks in many countries.
Go to sleep on your side from now on. Studies link sleeping on your back in late pregnancy to a higher risk of stillbirth.

Typical weight gain so far: 6.6–9.8 kg
Your uterus: Fundal height ≈ 28 cm (±2 cm)

Weight gain range is for a pre-pregnancy BMI of 18.5–24.9 (IOM guideline). Your provider may advise differently.

What happens at the 28-week appointment

In the UK you’ll have a blood test to check your general health, iron levels and blood group. If your baby is at risk of rhesus disease, you’ll be offered an anti-D injection. Your midwife will also check your blood pressure and urine, measure your bump, and ask about the baby’s movements and how you’re feeling.

The NHS also offers the RSV vaccine around now, to help protect your baby in their first months. It is best from 28 weeks and can be given later, right up until you go into labour. Timing is different in some other countries.

Why sleep on your side from 28 weeks

The safest position to fall asleep in is on your side, left or right. A pooled analysis of five studies found that going to sleep on your back was linked with about 2.6 times the odds of late stillbirth, with no difference between left and right. This may be because of reduced blood flow and oxygen to the baby.

Keep that in proportion, because the overall risk is low: around 3 to 4 in 1,000 births in the UK are stillbirths. If you wake up on your back, don’t worry. Just turn onto your side before going back to sleep. A pillow under your bump or between your knees can make side sleeping more comfortable.

Signs of early labour at 28 weeks

Call your maternity unit urgently if you’re under 37 weeks and think labour may have started. Signs include regular tightenings, period-like pain, backache, or your waters breaking. Don’t wait to see if it settles. It’s always fine to be checked and told that all is well.

Scans, tests and checkups

This week

Know your baby’s movements Self-care
Get to know your baby’s pattern. If movements slow down, change or stop, contact your maternity unit straight away. Don’t wait until the next day.
This week

Glucose test (gestational diabetes) Blood test
A sugary drink followed by blood sugar checks. The UK offers it based on risk factors. The US screens almost everyone.
This week

Whooping cough (Tdap) vaccine Vaccine
Antibodies pass to the baby and protect them in their first weeks. The US recommends 27–36 weeks. The NHS offers it from 16 weeks, usually around 20, and ideally before 32.
This week

Anti-D (if Rh-negative) & repeat bloods Blood test
If your blood group is Rh-negative, anti-D immunoglobulin is offered around 28 weeks. Blood count and antibodies are often rechecked.
This week

RSV vaccine Vaccine
Protects newborns from RSV, a serious lung infection. The US gives it at 32–36 weeks in RSV season. The UK offers it from 28 weeks. Check local guidance.

See the full scan and test timeline

Real size, next to an adult hand

Adult hand 18.5 cmbaby 25.6 cm curled up

Growth curve

Typical weight by week: WHO median from week 20, approximate before that. Healthy babies vary widely.

When to call your midwife or doctor at 28 weeks

Call your midwife, doctor or maternity unit straight away, day or night, if you have any of these:

A change in your baby’s usual pattern of movement. Call straight away rather than waiting until the next day.
Vaginal bleeding, or a gush or steady trickle of fluid.
Severe belly pain that doesn’t go away.
A severe headache, vision changes, pain under your ribs, or sudden swelling of your face, hands or feet. These can be signs of pre-eclampsia.
Regular tightenings, period-like cramps or lower back pressure that keep coming. This could be early labour.
Intense itching, especially on your hands and feet, which can be a sign of a liver condition called cholestasis.
Fever of 38 °C (100.4 °F) or higher, or pain or burning when you pee.
Pain or swelling in one leg, chest pain, or sudden shortness of breath. These can be signs of a blood clot.
Feeling very low, hopeless or anxious most days. If you feel you might harm yourself, get emergency help.

Based on NHS and ACOG guidance. This list isn’t complete. If something feels wrong, call anyway. In an emergency, call your local emergency number.

Tip for this week

If you wake up on your back, don’t worry. Just roll onto your side. What matters most is the position you fall asleep in.

Myth or fact?

Is it dangerous to sleep on your back while pregnant?

Partly true

In the third trimester (from 28 weeks), going to sleep on your side is recommended. Earlier in pregnancy, back sleeping is fine.

Read the evidence

Common questions at this stage

All common questions

More myths around week 28

Questions people ask about week 28

Why should I sleep on my side after 28 weeks?

Lying on your back puts the weight of the uterus on major blood vessels. Research found that going to sleep on your back after 28 weeks is associated with a higher risk of stillbirth, so going to sleep on your side (either side) is recommended.

How big is the baby at 28 weeks?

About 37.6 cm from head to heel and around 1.2 kg, roughly the size of an eggplant (aubergine).

References

Advice differs between countries, so follow your own care team’s plan. Weights from week 20 are the WHO median, and earlier weights are approximate. How we check this.