Babies are just amazing creature of God. It is a imaginary situation how ony two microscopic gametes sperm and the egg fuses and develop into a baby . For nine months a mother carry her baby in her womb , protect her , feed her and finally give birth. But why babies cry when they born.
Women womb environment is not just like our natural environment . In womb a baby take oxygen by mother only . But when they born now they have to inhale and exhale . So to start the natural function of body they cry.
Doctors do everything to them cry , if a baby don't cry he may be died. So first cry of a baby is very important . The major organs like hear ,lungs , kidneys start working after they cry.
Also after birth there is anew beginning of a child's life so they cry to forgot his womb life and start a new life.
Hope you will be satisfied with my answer!!
Thank you!!