🤰 First trimester
5 weeks pregnant
Your baby is about the size of a sesame seed
By Emma Whitfield · Pregnancy & Baby Writer
Your baby at 5 weeks
The neural tube — which becomes the brain and spinal cord — is forming, and a very early heart is beginning to beat. This is a critical developmental window, which is why folic acid matters most now.
Your body at 5 weeks
Pregnancy hormones (hCG) are rising fast, and this is when morning sickness, sore breasts and fatigue often begin. Some people feel completely normal, which is also fine.
Common symptoms this week
- Nausea beginning (any time of day)
- Sore breasts
- Needing to wee more often
- Fatigue and mood swings
Symptom lists are typical, never exhaustive — and having none of them is normal too.
Focus this week
Check any regular medicines with a pharmacist or GP, and avoid alcohol and smoking. There's no safe known level of alcohol in pregnancy.
Week 5 checklist
- Check any regular medicines with a pharmacist or GP
- Stop alcohol and smoking completely
- Note the first day of your last period — every appointment will ask for it
5 weeks pregnant: common questions
Is it normal to have no symptoms at 5 weeks pregnant?
Completely normal. Symptom timing and intensity vary enormously — some people feel very sick from week 5, others feel nothing until week 7 or 8, and a lucky few sail through with almost no sickness at all. Absence of symptoms says nothing about how the pregnancy is progressing.
How big is my baby at 5 weeks pregnant?
At 5 weeks, your baby is approximately the size of a sesame seed. These are approximate averages — every baby grows at its own pace.
What's happening at 5 weeks pregnant?
The neural tube — which becomes the brain and spinal cord — is forming, and a very early heart is beginning to beat. This is a critical developmental window, which is why folic acid matters most now. For you: pregnancy hormones (hcg) are rising fast, and this is when morning sickness, sore breasts and fatigue often begin. some people feel completely normal, which is also fine.
Which trimester is 5 weeks?
5 weeks pregnant is in the first trimester. The first trimester runs to the end of week 12, the second from weeks 13 to 26, and the third from week 27 to birth.
Sources & further reading
This is general information, not medical advice — every pregnancy is different. For anything that worries you, and for all your antenatal care, speak to your midwife or GP. If your baby's movements ever slow down or change, contact your maternity unit immediately, day or night. Reviewed July 2026.