Second trimester
23 weeks pregnant: what is happening this week
Week 23 of 42worked example
28.9 cm
- Measured
- head to heelabout the size of a large mango
- This week runs
- Thu, Jun 4, 2026 to Wed, Jun 10, 2026
- Days to the estimated due date
- 126
- Term window (37-42 weeks)
- Thu, Sep 17, 2026 to Thu, Oct 22, 2026
The NHS publishes this figure for week 23, about the size of a large mango. It is an average from patient guidance rather than a measurement of any particular pregnancy, and the measurement basis changes at week 20 - see the note below the dates.
28.9 cm head to heel and the limbs have caught up with the body, so the proportions are approaching those of a newborn rather than the enormous-headed shape of the first trimester. Breathing practice continues and the sleep and wake pattern is more defined. Movements can now sometimes be seen from the outside, which is the point at which a partner stops taking somebody's word for it. On the maternal side, ribs are the story this week: the ribcage is being pushed outwards to make room, which produces a specific ache under the bra line and contributes to breathlessness. Colostrum may leak. This is a good week to start a conversation that is easy to defer - what happens with money. Statutory maternity pay is not a salary, the drop is usually significant, and it is much better modelled on a spreadsheet in week 23 than discovered in month two of leave. If either of you has been avoiding that arithmetic because it feels unromantic, do it anyway; it is one of the few pregnancy tasks that gets harder the longer it waits.
Put your own dates on week 23
- Week 1 began
- Thu, Jan 1, 2026
- Week 23 begins
- Thu, Jun 4, 2026
- Week 23 ends
- Wed, Jun 10, 2026
- Estimated due date
- Thu, Oct 8, 2026
Dates run on ACOG's 280-day convention, the same arithmetic as the due date calculator. Share this week with your dates: /pregnancy/week-23?s=d:2026-10-08
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What the NHS describes this week
- The NHS puts the foetus at around 28.9 cm from head to heel this week.
- The limbs are now in proportion with the body.
- Movements may become visible from outside the abdomen, and practice breathing and sleep-wake patterns continue.
What happens around now
Rib pain and breathlessness are common as the ribcage expands. Colostrum may leak from about now. Both are listed by the NHS among the ordinary changes of this stage.
On the measurement. The NHS publishes a length for each week from 4 to 40. Up to week 19 it is measured head to bottom (crown to rump, the measurement a scan takes while the legs are curled). From week 20 it is measured head to heel, which is why the figure jumps from 15.3 cm at week 19 to 25.6 cm at week 20 - the baby did not grow 10 cm in a week, the ruler changed. The NHS states the change on its week 20 page.
Where week 23 comes from
- NHS: week 23 of pregnancy
- NHS, Week-by-week guide to pregnancy — the guide these weeks are built from
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