Fetal Development Weeks 18 Through 21

Week 18

The unique swirls and whorls that are your baby's fingerprints begin to appear at the tips of her fingers this week. Her hands begin to make grasping motions, and she might even start sucking her thumb. This self-soothing habit can stick around into a child's toddlerhood and beyond, but all kids give it up eventually.

The placenta, that all-important nurturing organ, is now almost as big as the baby herself. Besides providing her with a steady diet of nutrients and oxygen, this dark blobby mass also receives waste products from the fetus's blood and deposits them in the mother's blood. The waste is then filtered out by the mother's kidneys.