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1st trimester

07th Nov 2023

Your baby at 4 weeks: Week-by-week guide to pregnancy


pregnancy week 4 poppy seed picture

Welcome to week 4 of your pregnancy! This week, your baby is as big as a poppy seed. Here’s what else you can expect this week.

Your baby

Your baby is the size of a poppy seed, just a little bigger than this full stop. The fertilised egg (or eggs) — known as a zygote — has arrived in your womb and implanted into its wall. It has divided into two; one group of cells will become the embryo, the other its life support mechanism, the placenta.

The placental cells immediately begin to produce Human Chorionic Gonadotrophin (hGC) the hormone that a pregnancy test looks for before it shows you those life-changing blue lines.


Early pregnancy symptoms including sore boobs, feeling bloated, and moodiness. If you’re not expecting to be pregnant you can easily mistake them for PMS – particularly if you experience implantation bleeding and mild cramping.

Your heart rate is already increasing. Notice a strange taste in your mouth? It’s another early sign. At this point, the levels of hCG might not be sufficient to show a positive pregnancy test result, which is something to note.

Tip: It’s still early days in the life of your little poppy seed and while it may not feel like much is happening yet, there’s a lot going on behind the scenes.

Reading up on all the weird and wonderful things that are happening to you is a lovely way to relax in the early months of pregnancy. Check out our ‘Top 10 Books To Read When Pregnant’.

So how did you know you were pregnant??? Were there any odd signs hinting at the changes within?

’12 Women Reveal The Weird Signs That Hinted They Were Pregnant’