First Trimester
Week 3
Reviewed by Dr. Humaira Latif, OB-GYN & Ultrasound Specialist
Welcome to week 3 of your pregnancy. Here’s a gentle look at what to expect at 3 weeks pregnant — baby’s size, changes in your body, common 3 weeks pregnant symptoms and a caring tip from Dr. Humaira.
Baby's size
A ball of cells (blastocyst) — smaller than a poppy seed.
What's happening
Fertilization has happened. The blastocyst is traveling down the fallopian tube and beginning to implant into your uterine lining.
Your body
Implantation may cause very light spotting for some women; most feel nothing yet.
Common symptoms
- Light spotting (implantation)
- Mild cramping
- Breast tenderness beginning
When to call your doctor
- Heavy bleeding
- Severe one-sided pain (possible ectopic warning sign)
Dr. Humaira's tip
Avoid alcohol, smoking, and unnecessary medications from now on — even before a positive test.
Educational only — not a substitute for in-person medical advice. Always follow your own doctor's guidance.