Pregnancy Guide

3 Weeks Pregnant

Your baby is the size of a Crystal of Salt. Discover exactly what is happening to your body and your baby this week.

New pregnancy guide: Learn how weeks are counted, what each trimester means, and how to interpret your calculator results for better preparation and planning. Read the full guide

Week 3 in detail

Implantation week — the two-week wait

Baby this week

If fertilization happened, the blastocyst reaches the uterus and may implant in the lining. It splits into what will become the embryo and the placenta. Home tests often stay negative until closer to your missed period.

  • Implantation usually happens 6–10 days after ovulation
  • Very light spotting can occur — it is not a period
  • hCG production starts after implant, which is why tests lag

Your body this week

Most people feel nothing. Mild cramping or a smear of pink/brown spotting can be implantation. Heavy bleeding like a period is more likely a period. Do not diagnose from an app — test after a missed bleed.

  • The two-week wait is emotionally loud and physically quiet
  • Keep prenatals; skip new supplements you have not cleared with a clinician
  • A negative test today does not rule out a pregnancy that implanted late

Get ready

Be patient with testing. First-morning urine after a missed period is more reliable than testing early. Use the checklist above for rest and folic acid; skip high-impact experiments you would not want during an unknown implant.

A general guide, not medical advice. Scan timing and symptoms vary — ask your clinician.

Baby Growth Curve

This chart visualizes the average length of the baby from week 1 to 40. Values are based on standard clinical averages.

← Week 2 Week 4 →