Germinal Period
The first stage of prenatal development — roughly the first two weeks after conception.
What happens
Section titled “What happens”- Fertilization — a sperm and an egg join to form a single cell, the zygote, carrying a complete new set of genetic instructions.
- Cleavage — the zygote divides repeatedly as it travels down the fallopian tube, becoming a hollow ball of cells.
- Implantation — that ball burrows into the lining of the uterus, establishing the connection that will become the placenta.
Key idea
Section titled “Key idea”In just two weeks the single starting cell becomes an implanted, multicellular structure — but one in which no body parts have yet formed. Many pregnancies end at this stage, often unnoticed.