4 weeks pregnant
At 4 weeks you are in month 1 and the first trimester. Your baby is about the size of a poppy seed: 0.1 cm.
As big as
poppy seed
Length
0.1 cm
Month
1
Trimester
first trimester
To go
252 days
Averages. Measured crown to rump up to week 20, crown to heel after that. Healthy babies vary a lot.
Your baby this week
The embryo has formed; the very first cell layers are taking shape.
Your body
Your period doesn't arrive; a test can come back positive now.
Good to know
Implantation sometimes causes light spotting around the day your period was due. It is not a period.
To sort around these weeks
- Take a pregnancy test and book a first appointment with a midwife or your GP.
- Work out your due date with the calculator so you know where you are.
Follow your pregnancy week by week
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Frequently asked questions
How many months is 4 weeks pregnant?
4 weeks pregnant falls in month 1 of your pregnancy.
Which trimester is 4 weeks?
At 4 weeks you are in the first trimester.
How big is a baby at 4 weeks?
On average 0.1 cm, about the size of a poppy seed. Healthy babies vary a lot.
How long to go at 4 weeks?
Until your due date (40 weeks): 36 weeks, 252 days.
All weeks
General information, not medical advice. If in doubt, call your midwife or GP. Sources: WHO fetal growth charts (Kiserud et al., PLoS Med 2017); Robinson and Fleming 1975; NHS, Your pregnancy and baby guide.