The fluttering sensation you feel in your abdomen this month means the fetus is moving -- and that's living proof that his muscles and limbs are getting stronger and his bones are hardening. He can kick, turn, curl his toes, frown, or purse his lips -- even hiccup -- all while floating around in about a pint of amniotic fluid, made up mostly of fetal urine. (Though that may sound yucky, it's not harmful to the fetus, who actually swallows it.)
Baby's sucking reflex has also developed. If his hand floats to his mouth, he can suck his thumb. At 5 inches and 4 ounces, the fetus is now big enough to fill the palm of your hand.