Third trimester

33 weeks pregnant: what is happening this week

Week 33 of 42worked example

43.7 cm

Measured: head to heelabout the size of a pineapple
This week runs: Thu, Aug 13, 2026 to Wed, Aug 19, 2026
Days to the estimated due date: 56
Term window (37-42 weeks): Thu, Sep 17, 2026 to Thu, Oct 22, 2026

The NHS publishes this figure for week 33, about the size of a pineapple. 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.

43.7 cm, pineapple-sized, and the brain and nervous system are described by the NHS as fully developed. Bones are hardening, with one deliberate exception: the skull plates stay soft and separated, so the head can compress slightly on the way out and then expand again afterwards. That is why newborn heads are sometimes an odd shape for a few days and why it resolves without anyone doing anything. There is often a heavy feeling low in the pelvis by now, which is the head settling downwards. Braxton Hicks continue. Fatigue is substantial and it is not the same fatigue as the first trimester - that one was chemical, this one is mechanical. Seven weeks to the estimate, and this is the sensible week for the hospital bag. Not hers, which she will pack whatever anyone says. Yours: phone charger with a long cable, food that survives a rucksack, cash and card for parking, a change of clothes, and something to read at three in the morning when nothing is happening.

Put your own dates on week 33

Your estimated due dateNothing you type here leaves your browser. Without a date the panel shows a worked example built from a last period of Thu, Jan 1, 2026.

Week 1 began: Thu, Jan 1, 2026
Week 33 begins: Thu, Aug 13, 2026
Week 33 ends: Wed, Aug 19, 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-33?s=d:2026-10-08

Everything you type here is computed in your browser. Nothing you enter is stored on a server, sent anywhere, or shared — there is no account and no health data to leak.

What the NHS describes this week

The NHS puts the foetus at around 43.7 cm from head to heel this week.
The brain and nervous system are described as fully developed.
The bones are hardening, except the skull bones, which stay soft and separated.

What happens around now

A heavy feeling in the pelvis is common as the head settles lower. The NHS suggests having a hospital bag ready from around 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 33 comes from

NHS: week 33 of pregnancy
NHS, Week-by-week guide to pregnancy — the guide these weeks are built from

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