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Pregnancy Snapshot

3 to

4 weeks pregnant

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 or fertilization,
not from the beginning of your last menstrual period. One month equals 4 weeks.)

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

The heart begins beating! (3 wks, 1 day)

The amnion surrounds the embryo with a fluid-filled sac. (4 wks)

The umbilical cord is in place. (4 wks)

The heart beats more than 100 times per minute. (4 wks)

Limb buds (soon-to-be arms and legs) appear. (4 wks)

Part of the brain that will control coordination is present. (4 wks)

The skin is so thin, you can see through it! (4 wks)

• Part of the thyroid gland appears. (3 wks, 1 day)

• A tiny trachea or windpipe is forming. (4 wks)

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