Week 5 of Pregnancy
The heart begins to form and the neural tube starts closing — a critical week for development.
Fetal size
Sesame seed
- Length
- 0.2 cm
- Crown-rump (CRL)
- Weight
- Not yet measurable
Fetal development
- The neural tube (future brain and spinal cord) begins to form.
- A primitive heart tube starts beating.
- The embryo is roughly 2mm long.
Maternal changes
- Morning sickness can begin in earnest.
- You may urinate more often and feel unusually tired.
Recommended checkups
- Make sure you are taking 400–800µg of folic acid daily — this is the key window for neural tube defect prevention.
Jump to week
Textbook averages. Individual variation is wide and this is not medical advice — confirm with your OB.