The embryo officially becomes a fetus
Baby this week: about 3.1 cm — crown to rump · about 4 g
≈ 3.1 cm — about the size of a kumquat
Illustration enlarged for clarity — the amber marker shows true relative size
Your baby this week
- The medical term switches from 'embryo' to 'fetus' this week
- Fingernails and toenails begin to form
- The outline of the nose and earlobes becomes more defined
- Bones start to harden, beginning the process of ossification
Your body this week
- Some notice their first hint of a baby bump starting to show, though this varies a lot
- Energy levels may still be low, especially if nausea is ongoing
This week's tip: If morning sickness makes it hard to eat balanced meals, focus on whatever nutritious foods you can tolerate right now — variety can wait.
When to get help now
Call emergency services now or go to an emergency department now if you have sudden, severe tummy pain, pain in the tip of your shoulder, feel very weak, faint or dizzy, or have heavy bleeding that soaks a pad soon after putting it on. For lighter bleeding or spotting, or pain low down on one side, contact your doctor, maternity unit or an early pregnancy unit today.
Sizes and milestones are typical ranges — every pregnancy runs on its own clock. Educational content; your prenatal care team's guidance always comes first.