Here's a month-by-month guide to your baby's development:

Month 1

  • Tiny limb buds, which will grow into arms and legs, appear.
  • The embryo looks like a tadpole.
  • The heart and lungs begin to form. By the 25th day, the heart starts to beat.
  • The neural tube, which becomes the brain and spinal cord, begins to form.
  • At the end of the first month, the embryo is about 1/2 inch long and weighs less than 1 ounce.

Month 2

  • All major body organs and systems are formed but not completely developed.
  • The early stages of the placenta, which exchanges nutrients from your body for waste products produced by the baby, are visible and working.
  • The ears, ankles, and wrists form. The eyelids form and grow but are sealed shut.
  • Fingers and toes develop.
  • By the end of the second month, the fetus looks more like a person than like a tadpole, is about 1 inch long and still weighs less than 1 ounce.

Month 3

  • After 8 weeks as an embryo, the baby now is called a "fetus."
  • The fingers and toes have soft nails.
  • The mouth has 20 buds that will become "baby teeth."
  • You can hear your baby's heartbeat for the first time (10 to 12 weeks) using a special instrument called a Doptone.
  • For the rest of pregnancy, the body organs will mature, and the fetus will gain weight.
  • By the end of this month, the fetus is 2 1/2 inches long and weighs a little over 1 ounce.

Month 4

  • The fetus moves, kicks, and swallows.
  • The skin is pink and transparent.
  • The umbilical cord continues to grow and thicken to carry enough nourishment from mother to fetus.
  • The placenta is fully formed.
  • By the end of the fourth month, the fetus is 6 to 7 inches long and weighs about 5 ounces.

Month 5

  • The fetus becomes more active, turning from side to side and sometimes head over heels.
  • The fingernails have grown to the tips of the fingers.
  • The fetus sleeps and wakes at regular intervals.
  • The fetus has a month of rapid growth. At the end of the fifth month, the fetus is 8 to 12 inches long and weighs 1/2 to 1 pound.

Month 6

  • The skin is red and wrinkled and covered with fine, soft hair.
  • The eyelids begin to part and the eyes open.
  • The finger and toe prints can be seen.
  • The fetus continues its rapid growth. At the end of the sixth month, the fetus is 11 to 14 inches long and weighs 1 to 1 1/2 pounds.
  • If born now, the fetus might survive with intensive care.

Month 7

  • The fetus can open and close its eyes and suck its thumb.
  • The fetus exercises by kicking and stretching.
  • The fetus responds to light and sound.
  • If born now, the fetus has a good chance for survival.
  • The fetus is now about 15 inches long and weighs about 3 pounds.

Month 8

  • Rapid brain growth continues.
  • The fetus is too big to move around much but can kick strongly and roll around.
  • You may notice the shape of an elbow or heel against your belly.
  • The bones of the head are soft and flexible to make it easier for the baby to fit through the birth canal.
  • The lungs may still be immature. If born now, before 37 weeks, the fetus is premature but has an excellent chance for survival.
  • The fetus is now about 18 inches long and weighs about 5 pounds.

Month 9

  • At 37 to 40 weeks, your baby is full term.
  • The baby's lungs are mature and ready to work on their own.
  • During this month the baby gains about 1/2 pound a week.
  • The baby moves into position to be born, usually dropping into a head-down position and resting lower in the mother's belly.
  • By the end of the ninth month, the baby weighs 6 to 9 pounds and is 19 to 21 inches long.