4 weeks pregnant
A tiny new beginning.
In short
At 4 weeks your baby is about the size of a poppy seed. A tiny new beginning.
- First trimester, week 4 of about 40.
- Contact your GP to confirm the pregnancy. Your GP can register you for the Maternity and Infant Care Scheme, which covers your pregnancy care free of charge.
Your baby is a tiny ball of cells that has just settled into the lining of your womb. The outer cells are linking up with your blood supply and will go on to form the placenta.
How big is my baby at 4 weeks?
At 4 weeks your baby is about the size of a poppy seed. 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 4 weeks?
- Your baby is a tiny ball of cells that has just settled into the lining of your womb.
- The outer cells are linking up with your blood supply and will go on to form the placenta.
- The inner cells are arranging into 3 layers that will grow into every part of your baby's body.
- For now, a tiny yolk sac supplies all the nourishment your baby needs.
What changes for me at 4 weeks pregnant?
- You probably won't look or feel pregnant yet.
- Pregnancy is counted from the first day of your last period, so your baby was conceived only about 2 weeks ago.
- Some people notice early signs such as tiredness, tender breasts or needing to pee more often.
What is a good tip for this week?
Take folic acid every day. If you haven't started yet, it is not too late to start now.
What can a partner do this week?
Offer to come along to the first GP visit and be patient if tiredness kicks in early.
What should I know in Ireland at 4 weeks?
- Contact your GP to confirm the pregnancy. Your GP can register you for the Maternity and Infant Care Scheme, which covers your pregnancy care free of charge.
- You don't need a medical card or GP visit card for free public maternity care, but you will need your PPS number to register.
When to get help: If you have bleeding from your vagina or severe tummy pain, contact your midwife, GP or maternity unit straight away. 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.