Illustration of a baby at week 23 inside the womb in cross-section, with the placenta and umbilical cord — Womb in cross-section, enlarged to show detail. Not true size.

Second trimester, week 23

23 weeks pregnant: Startled by loud sounds

Size of a: Grapefruit
Length: 28.9 cm head to heel
Weight: 565 g WHO median
Heart rate: 110–160 bpm typical range
Due date: 119 days away 57% 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 23 weeks pregnant, your baby is about the size of a grapefruit: roughly 28.9 cm from head to heel, weighing about 565 g. You’re in your second trimester, with about 17 weeks to go until your due date.

Your baby this week

Hearing is improving, and loud sounds can make the baby jump.
Rapid eye movements are appearing, a sign of maturing sleep cycles.
The lungs are developing the cells that will make surfactant, the substance that helps air sacs stay open.

Your body this week

Your gums may be sore or bleed when you brush, so keep flossing gently.
Some people notice a faster pulse and occasional breathlessness.
Your glucose test is coming up soon (24–28 weeks).

Typical weight gain so far: 4.6–7.2 kg
Your uterus: Around your belly button

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

Scans, tests and checkups

From week 24

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.
From week 24

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.
From week 27

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.

See the full scan and test timeline

Real size, next to an adult hand

Adult hand 18.5 cmbaby 19.7 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 23 weeks

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

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.
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

Know the warning signs of pre-eclampsia: severe headache, vision changes, pain below the ribs, or sudden swelling of the face, hands or feet. Call your provider if you notice them.

Myth or fact?

Can babies hear in the womb?

True

Yes. In one study, babies first responded to a sound at 19 weeks, and most responded by 27 weeks. Newborns recognise their mother’s voice.

Read the evidence

Common questions at this stage

All common questions

Questions people ask about week 23

Can the baby hear music at 23 weeks?

Yes, muffled. Low-frequency sounds pass through best. Loud music close to your belly isn’t necessary. Normal talking and singing are plenty.

What are the signs of pre-eclampsia?

High blood pressure plus symptoms such as a severe headache, blurred vision or flashing lights, pain just below the ribs, vomiting, or sudden swelling of the face, hands or feet. Seek care promptly if you notice any of these.

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.