Baby Development Timeline

  • 4 Weeks

    4 Weeks
    At this point the baby is developing the structures that will eventually form his face and neck. The heart and blood vessels continue to develop. And the lungs, stomach, and liver start to develop. A home pregnancy test would show positive.
  • 8 weeks

    8 weeks
    The baby is now a little over half an inch in size. Eyelids and ears are forming, and you can see the tip of the nose. The arms and legs are well formed. The fingers and toes grow longer and more distinct.
  • 12 weeks

    12 weeks
    The baby measures about 2 inches and starts to make its own movements. You may start to feel the top of your uterus above your pubic bone. Your doctor may hear the baby's heartbeat with special instruments. The sex organs of the baby should start to become clear.
  • 16 weeks

    16 weeks
    The baby now measures about 4.3 to 4.6 inches and weighs about 3.5 ounces. You should be able to feel the top of your uterus about 3 inches below your belly button. The baby's eyes can blink and the heart and blood vessels are fully formed. The baby's fingers and toes have fingerprints.
  • 20 weeks

    20 weeks
    The baby weighs about 10 ounces and is a little more than 6 inches long. Your uterus should be at the level of your belly button. The baby can suck a thumb, yawn, stretch, and make faces. Soon -- if you haven't already -- you'll feel your baby move, which is called "quickening."
  • 24 weeks

    24 weeks
    The baby weighs about 1.4 pounds now and responds to sounds by moving or increasing his pulse. You may notice jerking motions if he hiccups. With the inner ear fully developed, the baby may be able to sense being upside down in the womb.
  • 28 weeks

    28 weeks
    The baby weighs about 2 pounds, 6 ounces, and changes position often at this point in pregnancy. If you had to deliver prematurely now, there is a good chance the baby would survive. Ask your doctor about preterm labor warning signs. Now is the time to register for birthing classes. Birthing classes prepare you for many aspects of childbirth, including labor and delivery and taking care of your newborn.
  • 32 weeks

    32 weeks
    The baby weighs almost 4 pounds and is moving around often. The baby's skin has fewer wrinkles as a layer of fat starts to form under the skin. Between now and delivery, your baby will gain up to half his birth weight. Think about breastfeeding. You may notice a yellowish fluid leaking from your breasts. That is colostrum, and it happens to get your breasts ready for making milk. Most women go to the doctor every two weeks at this stage of pregnancy.
  • Birth

    Birth
    A mother's due date marks the end of her 40th week. The delivery date is calculated using the first day of her last period. Based on this, pregnancy can last between 38 and 42 weeks with a full-term delivery happening around 40 weeks. Some post-term pregnancies -- those lasting more than 42 weeks -- are not really late. The due date may just not be accurate. For safety reasons, most babies are delivered by 42 weeks. Sometimes the doctor may need to induce labor.
  • 36 weeks

    36 weeks
    So your baby's overall rate of growth is as important as the actual size. On average, a baby at this stage is about 18.5 inches and weighs close to 6 pounds. The brain has been developing rapidly. Lungs are nearly fully developed. The head is usually positioned down into the pelvis by now. Your baby is considered at 'term' when he is 37 weeks. He is an early term baby if born between 37-39 weeks, at term, if he's 39-40 weeks and late term if he's 41-42 weeks.