First trimester
3 weeks pregnant
Baby is about the size of a poppy seed.
Week 3 of 40 · in your first trimester · Updated
Your baby this week
A fertilized egg is dividing rapidly and traveling to your uterus to implant.
- The zygote travels down the fallopian tube while dividing — first into 2 cells, then 4, then 8.
- By day 5 it's a blastocyst (~100 cells) and reaches the uterus.
- Genetic makeup — including sex chromosomes — is already fully set at conception.
Your body this week
You might notice mild cramping. It's still way too early for a positive test.
- Implantation usually happens at the end of this week, when the blastocyst burrows into the uterine lining.
- Some people get light spotting (implantation bleeding) — brown or pink, much lighter than a period.
- hCG hormone starts to be produced but is too low to detect on a home test yet.
Common symptoms
- Light spotting
- Mild cramps
- Heightened sense of smell
- Tender breasts
Things to do this week
- Keep up the prenatal vitamin
- Stay hydrated
- Listen to your body
For partners this week
The waiting game
- It's still too early for a test. Be patient together.
- Plan something nice that takes both your minds off waiting.
Typical visits around this week
Based on a typical schedule in Ontario. Your doctor or midwife sets the actual timing.
Coming up
First prenatal visit
Weeks 6–12
Book with your doctor or midwife as soon as you know you're pregnant. This is usually the longest visit: your health and family history, medications, blood pressure and weight, and routine blood and urine tests (including your blood type and Rh factor). Your provider will also talk about your due date and the screening options ahead.
Questions to ask →Questions to ask ↑
- When is my estimated due date, and how was it worked out?
- Are my current medications and supplements okay to keep taking?
- Who will care for me during pregnancy and birth, and where would I give birth?
- Who do I call with questions or worries between visits?
- Which vaccines should I plan for this pregnancy?
Dating ultrasound
Weeks 7–12
An early ultrasound that measures the baby to confirm how far along you are. Dating is most accurate between about 7 and 12 weeks, and the scan also confirms the pregnancy is in the uterus.
Questions to ask →Questions to ask ↑
- Does this scan change my due date?
- Can my partner come into the room?
- Do I need a full bladder, and how should I prepare?
- When will my provider get the results?
When to call your doctor or midwife
Bleeding, fluid leaking, a bad headache or vision changes, or baby moving less than usual all need a call. See the warning signs and who to call →
Follow your pregnancy week by week in MyBabyBase.
A due-date countdown, a mood and symptom journal, appointments, and a safe place for your documents — all in one hub.
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Further reading from health authorities
- Pregnancy — Government of Canada (Public Health Agency of Canada)
- Your pregnancy — Pregnancy Info, from the Society of Obstetricians and Gynaecologists of Canada (SOGC)
- Week-by-week guide to pregnancy — NHS (UK)
- Pregnancy — American College of Obstetricians and Gynecologists (ACOG)