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Fetal development: The first trimester

Week 6: The neural tube closes

The sixth week of pregnancy, or four weeks after conception, the neural tube along your baby's back is closing. The brain and spinal cord develop from the neural tube. The heart and other organs also start to form.

Structures needed to form the eyes and ears develop. Small buds appear that will soon become arms. Your baby's body begins to take on a C-shaped curve.