Which happens to a developing child first?

Answer 1

Depends on when you consider it a child. First it's a Zygote, a fertilized egg, and then a blastocyst. Medically it's not a child until it's born. But if we start with embryo you can read all about it in the link below. Someone wrote blood starts pumping and arms starts to develop but that is weeks later.

Blood pumps through the body.

or

Rhythmic breathing movements

Answer 2

The heart begins beating.

Answer 3

Development of hands (apex)

Answer 4

Blood pumps through the body

Answer 5

heart begins beating