Fertilization occurs in the fallopian tubes. The fertilized egg implants in the uterus and develops a placenta to receive nutrients from the mother's blood. The placenta secretes hormones like HCG, estrogen, and progesterone to sustain the pregnancy. As pregnancy progresses, the placenta takes over hormonal support from the corpus luteum. Near term, estrogen levels rise and progesterone falls, preparing the body for labor and delivery of the baby.