The neural tube — the start of the brain and spinal cord — begins to close
Baby this week: about 0.2 cm — crown to rump · under 1 g
≈ 0.2 cm — about the size of a sesame seed
Illustration enlarged for clarity — the amber marker shows true relative size
Your baby this week
- The neural tube, which will form the brain and spinal cord, starts to close
- A primitive heart tube is taking shape and will soon start beating
- Three distinct layers of cells are forming, each destined to build different organs and tissues
- The embryo is curved, with a visible head fold and tail fold
Your body this week
- Fatigue and breast tenderness are common as hormone levels rise quickly
- Some people notice a heightened sense of smell or an early wave of nausea
This week's tip: This is a good week to start, or confirm, a folic acid supplement — doctors usually recommend one in early pregnancy, and yours will confirm the dose that's right for you.
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.