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.