Quick Facts About Fetal Development
The heart begins to beat just 21 days after fertilization, or 5 weeks after the mother's last menstrual period began.
At 8 weeks, the embryo can respond to touch by reflex.
At 10 weeks, for the first time in development, the brain can make the muscles move on purpose.
By 18 weeks, fetal movement can usually be felt by the mother.
At 22 weeks, the baby is about 11 inches long and weighs about 1 pound.