Week 3 Pregnancy

First Trimester

Last reviewed: July 2026

3 weeks pregnant at a glance

You are in the first trimester.
Your baby is roughly the size of a microscopic grain of sand.
Symptoms like possible light spotting (implantation) may be noticeable.
Every pregnancy is different, so don't worry if your experience varies slightly.

You are 3 weeks pregnant and in your first trimester. Your baby is about the size of a microscopic grain of sand. This week's key development: The Meeting.

This page is for general pregnancy planning and date guidance only. It is not medical advice, diagnosis, or treatment. Pregnancy dates are estimates and can change after a scan or advice from your midwife, GP, or maternity team. Always speak to a qualified healthcare professional if you have symptoms, concerns, or questions about your pregnancy.

Week 2

Week 4

Baby's Development

Your baby is about the size of a microscopic grain of sand.

The Meeting — Conception has occurred, and a single fertilised cell is dividing rapidly as it travels toward your uterus. This blastocyst — a tiny sphere of potential — is beginning to nestle into your uterine lining by the end of this week.

Your Symptoms

Possible light spotting (implantation)
Mild cramping
Heightened sense of smell

Every pregnancy is different. You may experience all, some, or none of these symptoms — and that's completely normal. If anything concerns you, speak to your midwife.

NHS Appointments

None yet. You might not even know you're pregnant for another week or two!

Practical Advice for Week 3

Nutrition

Continue folic acid and vitamin D supplements without fail.
Eat calcium-rich foods like dairy, fortified plant milks, and leafy greens.
Small, frequent meals can help if you're starting to feel queasy.
Avoid liver and liver products (pâté) due to high vitamin A levels.

Exercise

Continue moderate exercise — your body is doing incredible work already.
Avoid contact sports or activities with a high risk of falling.
Pelvic floor exercises — keep going, they'll be invaluable later.
Walking after meals can help with digestion.

Wellbeing

You might not know you're pregnant yet, and that's completely normal.
If you are experiencing implantation spotting, try not to worry — it's very common.
Practise mindfulness or deep breathing if you're feeling anxious.
Lean on your support network — this is a time to be kind to yourself.

Preparation

If you get a positive test, contact your GP or midwife to start your maternity care.
Avoid alcohol, smoking, and recreational drugs.
Check your workplace maternity policy early — knowledge is power.
Start thinking about which hospital or birth centre you'd prefer.

Tip of the Week

Avoid alcohol and smoking as your baby begins its first critical stages of development.

Frequently Asked Questions for Week 3

How many months is 3 weeks pregnant?

At 3 weeks pregnant, you are roughly in your first month pregnant. Remember that pregnancy is typically measured in weeks rather than months for clinical accuracy.

What size is the baby at 3 weeks?

At 3 weeks, your baby is roughly the size of a microscopic grain of sand. Conception has occurred, and a single fertilised cell is dividing rapidly as it travels toward your uterus. This blastocyst

What are the common symptoms at 3 weeks pregnant?

Common symptoms at this stage include possible light spotting (implantation), mild cramping, heightened sense of smell. Remember that every pregnancy is unique, and it's normal to experience different symptoms.

Is 3 weeks in the first trimester?

Yes, 3 weeks falls within the first trimester.

Should I have a bump at 3 weeks?

It's very common not to show much at this stage. First-time mothers often 'pop' later.