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Pregnancy week by week

33 weeks pregnant

Your baby's brain is fully developed.

In short

At 33 weeks your baby is about the size of a pineapple, around 44.0 cm long and 2.1 kg. Your baby's brain is fully developed.

  • Third trimester, week 33 of about 40.
  • If you haven't had the whooping cough vaccine yet, ask your GP soon. It's recommended before 36 weeks and may be less effective after that.
About the size ofPineapple
Length, head to heel44.0 cm
Typical weight2.1 kg

Your baby's brain and nervous system are now fully developed. Bones keep hardening, but the skull bones stay soft so they can slide over each other during birth.

How big is my baby at 33 weeks?

At 33 weeks your baby is about the size of a pineapple, around 44.0 cm long and 2.1 kg. Before about 14 weeks babies are measured from crown to rump; after that the figure is head to heel. These are typical figures from fetal growth charts. Your own baby may be bigger or smaller, and your scans are what count.

What is my baby doing at 33 weeks?

What changes for me at 33 weeks pregnant?

What is a good tip for this week?

Start gathering things for your hospital bag, including your pregnancy notes, comfortable nightwear, maternity pads and newborn nappies.

What can a partner do this week?

Pack a small bag of your own too, with snacks, a phone charger and a change of clothes.

What should I know in Ireland at 33 weeks?

When to get help: Before 37 weeks, go to your maternity unit straight away if you have regular contractions that are getting stronger, a gush or trickle of fluid, bleeding or period-type pains. HSE: when to get help.

Want these updates on your phone? The Lullagram app has a free pregnancy section with this week-by-week guide, Irish dates worked out from your due date, a contraction timer and more. When your baby arrives, the baby tracker is ready in the same app.

Sources and guidance

This page is written to be consistent with the official guidance below. It is general information for parents in Ireland, not medical advice. Links checked 23 September 2026.