Growth before birth

Every person starts as one cell, the zygote, made when a sperm, the male gamete, joins an egg, the female gamete. It divides into a ball of cells that settles in the mother's womb (uterus), where the baby, called a foetus, grows for about nine months: the heart beats in the first month and all the main organs have formed by the end of the third. The umbilical cord joins it to the mother; its blood vessels bring food and oxygen from her blood and carry wastes back, so what the mother eats, drinks or breathes, smoke included, reaches the baby. Identical twins come from one zygote that split in two in its first days; non-identical twins from two eggs.