Pregnancy Snapshot

The first week

For a brief summary of development events during various
stages of pregnancy, choose any age* range from the drop-down menu.

(Ages are referenced from time of conception. One month equals 4 weeks.)

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Movie clip from The Biology of Prenatal Development. Buy Now!


Development begins with a single-cell embryo at conception!!! (Age: 0 days) One cell becomes two. (30 to 36 hours) With 12 to 16 cells, the embryo is shaped like a tiny bunch of grapes. (3 days) The site of the future back and chest can be seen. (4 days) The embryo begins to implant in the womb. (6 days)

*All prenatal ages are referenced from the time of fertilization (or conception).
One month is defined as exactly four weeks.