Fertilization, the union of an egg and a sperm , is the first step in a complex series of events that leads to pregnancy. Fertilization takes place in the fallopian tube. During the next few days, the fused egg and sperm move through the fallopian tube to the lining of the uterus. There it implants and starts to grow.
The cluster of cells that reaches the uterus will become the fetus and the placenta. The placenta functions as a life-support system during pregnancy. It delivers oxygen, nutrients, and hormones from mother to fetus.
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