Week 3: Conception
You’re 3 weeks pregnant — about 37 weeks to go. Your baby is roughly the size of a cluster of cells.
Size of
a cluster of cells
Length
—
Weight
—
Your baby this week
A sperm meets the egg and fertilisation happens. The single cell rapidly divides into a tiny ball of cells called a blastocyst as it travels down the fallopian tube toward the uterus.
Your body & how you might feel
You won’t feel any different yet, but the genetic blueprint — including your baby’s sex — is already set. Implantation is just days away.
Common symptoms at week 3
- No noticeable symptoms
- Possible faint twinges
This week’s tip: Keep caffeine moderate and skip alcohol while you wait to test — gentle habits now build a healthy foundation.
A gentle reminder: This is an estimate, not medical advice. Dates and figures are general guidance — every pregnancy is different. Your healthcare provider’s assessment, especially from an early ultrasound, always takes priority. Always speak with your provider about your pregnancy.
Week 3 FAQs
How big is the baby at 3 weeks?
At 3 weeks pregnant, your baby is roughly the size of a cluster of cells. These are typical averages — every baby grows at its own pace.
How many months is 3 weeks pregnant?
3 weeks pregnant is less than 1 month, in the first trimester, with about 37 weeks to go until your due date.
What are common symptoms at 3 weeks?
Common experiences around week 3 include no noticeable symptoms, possible faint twinges. Symptoms vary widely — contact your provider if anything worries you.