The process of pregnancy begins with intercourse, where sperm travels through the uterus into the fallopian tube. There, sperm can meet and fertilize an egg that has ovulated from the ovary. Once fertilized, the egg undergoes cellular division, developing into an embryo. On day 3, the embryo continues to divide, and by day 5, it forms a blastocyst. This blastocyst has two distinct parts: one destined to become the baby and the other to form the placenta. The blastocyst then hatches from its outer shell and implants itself in the uterus, marking the next stage of development where the embryo becomes a fetus, eventually leading to a baby. This natural progression forms the foundational understanding for various reproductive tests and treatments.