Week by week / First trimester
Week 3
Your baby is about the size of a cluster of cells. Here is what is happening, what you might feel, and the two or three things worth doing this week.
Size right now
A cluster of cells
- Trimester
- First
- To go
- 37 weeks
The baby
Fertilisation. A single cell becomes a ball of about 100 cells over the week and travels down the fallopian tube toward the uterus. Sex and eye colour were decided at the moment of fertilisation and nothing can change them now.
You
You feel nothing. There is no test that would show anything yet.
This week
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Averages, not targets. Babies vary a great deal and a scan that reads differently from this page is not a problem. Anything that worries you is a call to your midwife or doctor, not a search.