How a baby is made.
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Explanation of how pregnancy begins and early development: After intercourse aimed at conception, sperm travel through the uterus into the fallopian tube. If an egg that has ovulated from the ovary is present, sperm may meet and fertilize it in the tube. The fertilized egg develops over the next few days: by day 3 it is an embryo, and by day 5 it becomes a blastocyst with two parts—one that will form the baby and one that will form the placenta. The blastocyst then hatches from its surrounding egg shell and implants in the uterus. Following implantation, the embryo becomes a fetus and ultimately a baby.
Intercourse: Sexual activity through which sperm can enter the reproductive tract to try to achieve pregnancy.
Sperm: The male reproductive cell that can fertilize an egg.
Uterus: Also called the womb; the organ where an embryo implants and a pregnancy grows.
Fallopian tube: The tube between the ovary and uterus where the sperm and egg meet and fertilization occurs.
Ovulated: Refers to the release of a mature egg from the ovary.
Ovary: The organ that stores eggs and releases one during ovulation.
Fertilizes: When a sperm joins with an egg to start the process of development.
Egg: The female reproductive cell that can be fertilized by sperm.
Fertilized egg: The single cell formed right after the sperm and egg unite; the first stage of a new embryo.
Embryo: The early developing organism after fertilization and before it becomes a fetus.
Blastocyst: A day-5 embryo with two parts: one that will become the baby and one that will become the placenta.
Placenta: The organ that develops to provide oxygen and nutrients to the baby during pregnancy.
Hatch: When the blastocyst breaks out of its surrounding shell before implantation.
Egg shell: The protective outer layer around the early embryo that it must break through before implanting.
Implant: The process by which the embryo attaches into the lining of the uterus.
Fetus: The later stage of development after the embryo stage, which eventually becomes a baby.