Prenatal Development

By Maustin063416

  • Week 1-4

    The dividing fertilized egg moves down the fallopian tube toward the uterus.
    At about 5 days after fertilization, the cluster of dividing cells enters the uterus.
    At about 8–9 days after fertilization, the cluster of cells attaches to the lining of the uterus. http://www.acog.org/Patients/FAQs/Prenatal-Development-How-Your-Baby-Grows-During-Pregnancy

  • Week 5-8

    The placenta begins to form.
    The brain and spinal cord begin to form.
    The tissues that will form the heart begin to beat. The heartbeat can be detected during an ultrasound exam at about 6 weeks of pregnancy.
    Buds for limbs appear with paddle-like hands and feet.
    The eyes, ears, and nose begin to develop. Eyelids form, but remain closed.
    The genitals begin to develop.
    By the end of the eighth week, all major organs and body systems have begun to develop.

  • Week 9-12

    Buds for future teeth appear.
    Fingers and toes start to form. Soft nails begin to form.
    Bones and muscles begin to grow.
    The intestines begin to form.
    The backbone is soft and can flex.
    The skin is thin and transparent.
    The hands are more developed than the feet.
    The arms are longer than the legs.

  • Week 13-16

    Eyebrows, eyelashes, and fingernails form.
    Arms and legs can flex.
    External sex organs are formed.
    The placenta is fully formed.
    The outer ear begins to develop.
    The fetus can swallow and hear.
    The neck is formed.
    Kidneys are functioning and begin to produce urine.
    In male fetuses, the testicles begin to descend from the abdomen.
    Genitals become either male or female at week 14.

  • Week 17-20

    The sucking reflex develops. If the hand floats to the mouth, the fetus may suck his or her thumb.
    The skin is wrinkled, and the body is covered with a waxy coating and fine hair.
    The fetus is more active. You may be able to feel him or her move.
    The fetus sleeps and wakes regularly.
    Nails grow to the tips of the fingers.

  • Week 21-24

    Real hair begins to grow.
    The brain is rapidly developing.
    The eyes begin to open.
    Finger and toe prints can be seen.
    The lungs are fully formed but not yet functioning.

  • Week 25-28

    The eyes can open and close and sense changes in light.
    Lanugo begins to disappear.
    The fetus kicks and stretches.
    The fetus can make grasping motions and responds to sound.

  • Week 29-32

    With its major development finished, the fetus gains weight very quickly.
    Bones harden, but the skull remains soft and flexible for delivery.
    The different regions of the brain are forming.
    Taste buds develop, and the fetus can taste sweet and sour.
    The fetus may now hiccup.

  • Week 33-36

    The fetus usually stays in a head-down position in preparation for birth.
    The brain continues to develop.
    The skin is less wrinkled.
    The lungs are maturing and getting ready to function outside the uterus.
    Sleeping patterns develop.

  • Week 37-40

    The fetus drops lower into the pelvis.
    More fat accumulates, especially around the elbows, knees, and shoulders.
    The fetus gains about 1/2 pound per week during this last month of pregnancy.