Week 6 · Day 1
Your baby this week
About the size of a sweet pea 🫛
Week 6 — heart begins to beat
Typical length
4 – 6 mm (crown-rump)
Typical weight
under 1 g
What's forming now
- Tiny heart divides into chambers and starts beating (~110 bpm)
- Neural tube closes — the future brain and spinal cord
- Arm and leg buds appear as small paddles
- Eye spots, nostrils and ear pits form on the face
- Kidneys, liver and lungs start their earliest development
At this stage
Your baby is still a curved C-shaped embryo, about the size of a sweet pea, floating in the amniotic sac beside the yolk sac. This is one of the most important weeks — almost every major organ system is starting to form, which is why early prenatal vitamins and avoiding alcohol, smoking and certain medications matter so much right now.