Sizes are averages; from week 20 length is measured head to heel. Not sure which week you’re in? Calculate it.
Your baby at 3 weeks
Fertilisation happens in the fallopian tube. At that moment the baby’s genetic blueprint – including chromosomal sex – is set. The single-celled zygote divides again and again as it travels towards the uterus, becoming a hollow ball of around 100 cells called a blastocyst by about five days after fertilisation.
Your body at 3 weeks
You won’t feel pregnant yet. Progesterone from the corpus luteum (the empty follicle) keeps the uterine lining thick and nourishing.
Common symptoms this week
- Usually none
- Possible mild cramping or bloating
Tips & to-do list
- Treat yourself as pregnant: avoid alcohol, smoking and unprescribed medicines.
- If you need an X-ray or new medicine, tell the doctor you might be pregnant.
- Eat a balanced diet with plenty of dal, green leafy vegetables and fruit.
Check-ups and tests around this week
- Preconception check-up: haemoglobin, thyroid, blood sugar, rubella immunity
Week 3 at a glance
| At 3 weeks | |
|---|---|
| Trimester | First trimester |
| Pregnancy month | Month 1 of 9 |
| Weeks to due date | 37 weeks |
| Days pregnant | 21–27 days |
| Progress | 8% of 40 weeks |
When to call your doctor
Contact your doctor or go to hospital straight away if you notice:
- Heavy vaginal bleeding or passing clots
- Severe or one-sided abdominal pain, shoulder-tip pain or fainting (possible ectopic pregnancy)
- Vomiting so severe you can’t keep fluids down
- Fever above 38 °C or burning urination
Questions about 3 weeks pregnant
How many months is 3 weeks pregnant?
3 weeks pregnant falls in month 1 of pregnancy, in the first trimester. For medical purposes, weeks and days are more precise than months.
How big is my baby at 3 weeks?
At 3 weeks there is no visible embryo yet; pregnancy is counted from your last period, so the first weeks cover ovulation and conception.
Is it normal to have no symptoms at 3 weeks?
Yes. Every pregnancy is different, and symptoms come and go. Feeling well is not a sign that something is wrong. If you have concerns, or notice any warning signs listed on this page, contact your doctor.
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Medical disclaimer: The results and information on this page are estimates for general education only. They are not a diagnosis and do not replace advice from your gynaecologist, obstetrician or midwife. If you have pain, bleeding, reduced baby movements or feel unwell, contact your doctor or call 108 immediately. Read the full disclaimer.