Divider/Brand Symbol

Get inspired! Browse Questions

Your Developing Baby

Back to Questions

As an expectant parent, understanding the incredible journey of your developing baby is both fascinating and heartwarming. In this article, we'll explore your baby's growth and development during pregnancy. From the miraculous early stages to the beautiful transformations week by week, we'll provide insights into the remarkable process that brings you closer to life's miracle.

First trimester (week 1-week 12)

At four to five weeks:

  • Your baby's brain and spinal cord have begun to form.
  • The heart begins to form.
  • Arm and leg buds appear.
  • Your baby is now an embryo and one-twenty-fifth inch long.

At eight weeks:

  • All major organs and external body structures have begun to form.
  • Your baby's heart beats with a regular rhythm.
  • The arms and legs grow longer, and fingers and toes have begun to form.
  • The sex organs begin to form.
  • The eyes have moved forward on the face and eyelids have formed.
  • The umbilical cord is clearly visible.
  • At the end of eight weeks, your baby is a fetus and looks more like a human. Your baby is nearly 1 inch long and weighs less than one-eighth ounce.

At 12 weeks:

  • The nerves and muscles begin to work together. Your baby can make a fist.
  • The external sex organs show if your baby is a boy or girl. A woman who has an ultrasound in the second trimester or later might be able to find out the baby's sex.
  • Eyelids close to protect the developing eyes. They will not open again until the 28th week.
  • Head growth has slowed, and your baby is much longer. Now, at about 3 inches long, your baby weighs almost an ounce.
Learn more: First Trimester (week 1-12)

    Second trimester (week 13-week 28)

    At 16 weeks:

    • Muscle tissue and bone continue to form, creating a more complete skeleton.
    • Skin begins to form. You can nearly see through it.
    • Meconium (mih-KOH-nee-uhm) develops in your baby's intestinal tract. This will be your baby's first bowel movement.
    • Your baby makes sucking motions with the mouth (sucking reflex).
    • Your baby reaches a length of about 4 to 5 inches and weighs almost 3 ounces.

    At 20 weeks:

    • Your baby is more active. You might feel slight fluttering.
    • Your baby is covered by fine, downy hair called lanugo and a waxy coating called vernix. This protects the forming skin underneath.
    • Eyebrows, eyelashes, fingernails, and toenails have formed. Your baby can even scratch itself.
    • Your baby can hear and swallow.
    • Now halfway through your pregnancy, your baby is about 6 inches long and weighs about 9 ounces.

    At 24 weeks:

    • Bone marrow begins to make blood cells.
    • Taste buds form on your baby's tongue.
    • Footprints and fingerprints have formed.
    • Real hair begins to grow on your baby's head.
    • The lungs are formed, but do not work.
    • The hand and startle reflex develop.
    • Your baby sleeps and wakes regularly.
    • If your baby is a boy, his testicles begin to move from the abdomen into the scrotum. If your baby is a girl, her uterus and ovaries are in place, and a lifetime supply of eggs have formed in the ovaries.
    • Your baby stores fat and has gained quite a bit of weight. Now at about 12 inches long, your baby weighs about 1½ pounds.

    Learn more: Second Trimester (week 13-28)

    Third trimester (week 29-week 40)

    At 32 weeks:

    • Your baby's bones are fully formed, but still soft.
    • Your baby's kicks and jabs are forceful.
    • The eyes can open and close and sense changes in light.
    • Lungs are not fully formed, but practise "breathing" movements occur.
    • Your baby's body begins to store vital minerals, such as iron and calcium.
    • Lanugo begins to fall off.
    • Your baby is gaining weight quickly, about one-half pound a week. Now, your baby is about 15 to 17 inches long and weighs about 4 to 4½ pounds.

    At 36 weeks:

    • The protective waxy coating called vernix gets thicker.
    • Body fat increases. Your baby is getting bigger and bigger and has less space to move around. Movements are less forceful, but you will feel stretches and wiggles.
    • Your baby is about 16 to 19 inches long and weighs about 6 to 6½ pounds.

    Weeks 37–40:

    • At 39 weeks, your baby is considered full-term. Your baby's organs are ready to function on their own.
    • As you near your due date, your baby may turn into a head-down position for birth. Most babies "present" head down.
    • At birth, your baby may weigh somewhere between 6 pounds 2 ounces and 9 pounds 2 ounces and be 19 to 21 inches long. Most full-term babies fall within these ranges. But healthy babies come in many different sizes.

    Learn more: Third Trimester (week 29-40)

    by Lola&Lykke Team