Fetal Development Timeline

  • Week One

    Week One
    this stage is determined by your last menstrual period. The sperm has not entered the egg yet, but is well on its way.
  • Week Two

    Week Two
    At this stage, the sperm has entered the egg. Both sets on DNA from the parents begin merging, and the cell will divide multiple times.
    Fun Fact: The gender of the baby is determined at this time; wheather the sperm carries an X chromosome or a Y chromosome
  • Week Three

    Week Three
    At this time, the fertilized egg has traveled through the fallopian tubes and into the uterus. The cell continues to rapidly divide.
  • Week Four

    Week Four
    Now the fertilized egg is called a Blastocyst and is made up of 50-60 cells, and still multiplying!
    Fun Fact: the baby is now the size of a pinhead!
  • Week Five

    Week Five
    The blastocyst is now made up of a whopping 500 cells and is still multiplying. This is when the blastocyst divides into two separate parts: the placenta- a kind-of support system that nourishes the underdeveloped baby- and the actual baby.
    Fun Fact: The soon to be baby will now begin taking shape!
  • Week Six

    Week Six
    At this time: the spinal cord is beginning to close, the tiny heart starts beating, the first of the embryo's blood cells and vessels begin developing, and the brain divides itself into five parts. The embryo is well on its way to becoming a fetus.
  • Week Seven

    Week Seven
    At this stage, the embryo's heart begins to develop chambers and its arms and legs are now little stubs. Most of the baby's other organs and delicate features such as eyes and ears are also developing.
  • Week Eight

    Week Eight
    This far in the pregnancy, the baby will begin moving, although the mother wont be able to feel it for some time. The gums and teeth start taking form in this time period also.
  • Week Nine

    Week Nine
    The embryo-baby is now developing cartilage and bone.
    Fun Fact: The embryo's head is so large compaired to the body because the brain is growing so rapidly.
  • Week Ten

    Week Ten
    The embryo is now a fetus! At this point, the fetus will begin looking more baby-like.
    Fun Fact: The fetus is always moving, but the mother wont feel it just yet
  • Week Eleven

    Week Eleven
    The fetus is now developing taste buds and its fingers have separated. Its cartilages is beginning to calcify to later become bone. If the fetus is a boy, its testes will start producing the hormone testosterone.
  • Week Twelve

    Week Twelve
    The fetus' brain is fully formed and it can now feel pain. Its pancreas is functional and creating insulin already. Its kidneys are formed and the fetus can now urinate.
    Fun Fact: The fetus can get hiccups!
  • Week Thirteen

    Week Thirteen
    Its ribs are appearing and bone is replacing most cartilage.
    Fun Fact: The fetus already has its unique set of fingerprints!
  • Week Fourteen

    This marks the end of the first trimester and the beginning of the second. The fetus' sex organs are moving into place and its ears are fully formed.
  • Week Fifteen

    Week Fifteen
    Bones and muscle are still developing inside the fetus and its legs have grown longer than its arms. Its skin is still very transparent.
  • Week Sixteen

    Week Sixteen
    The fetus has learned to breathe, and in the process takes in alot of embiotic fluid.
  • Week Seventeen

    Week Seventeen
    The fetus will now store fat under its skin to keep it warm and provide energy. The skeleton is currently transforming from cartilage to bone.
  • Week Eighteen

    Week Eighteen
    The fetus can hear and its vocal cords are formed. The fetus can be startled by loud noises, and cant make any sounds even though it has vocal cords.
    Fun Fact: Some studies show that a baby's cry will imatate its mother's accent after its born!
  • Week Nineteen

    Week Nineteen
    The fetus will now have developed distinct and recognizable genitals. Its scalp hair is beginning to gro also.
    Fun Fact: A female fetus will have about 6 million eggs at this time, but she will only have about 1 million by the time of birth.
  • Week Twenty

    Week Twenty
    At this time during the pregnancy, nerve cells serving each of the senses; taste, smell, hearing, sight, and touch are now developing into their specialized area of the brain. The mother will probably be able to feel the baby kicking, moving, and rolling over.
    Fun Fact: Sounds a baby hears in the womb are often soothing to them after birth
  • Week Twenty One

    Week Twenty One
    The fetus' bone marrow has started making blood cells and the fetus will begin pulling sugar out of its amniotic fluid instead of soley relying on the placenta.
  • Week Twenty Two

    Week Twenty Two
    The fetus has now fully developed eyelids and eyebrows. If you speak loud enough, there is a chance the baby would be able to you.
  • Week Twenty Three

    Week Twenty Three
    The fetus will now develope its pigment color preordained by its parents genes. The fetus is now proportioned like a newborn.
  • Week Twenty Four

    Week Twenty Four
    At this stage, the fetus is beginning to fill out to look more like a newborn. Surfacant is a substance that helps the air sacs inflate easily and also keeps the small air sacs in our lungs from collapsing.
  • Week Twenty Five

    Week Twenty Five
    The structure of the spine is beginning to form and its brain is continuing to rapidly develop. Its nostrils have opened up and its mouth has become more sensative.
  • Week Twenty Six

    Week Twenty Six
    During this week, the fetus is most active and can be felt by the mother. Brain growth within the fetus continues to advance at a steady rate.
  • Week Twenty Seven

    Week Twenty Seven
    This week marks the end of the 2nd trimester and begins the last trimester of pregnancy. The fetus can open its eyes now. The retina in the back of its eyes are developing.
    Fun Fact: If the baby were to be born at this time, there is an 80% chance the baby will survive.
  • Week Twenty Eight

    Week Twenty Eight
    The fetus wont change much in this week except for size
    Fun Fact: If the baby were to be born at this time, it ould have a 90% chance of surviving.
  • Week Twenty Nine

    Week Twenty Nine
    The fetus' brain is busy at work developing billions of neurons, and in the process the head continues to increase in size. At this stage, babies ayes are almost always blue/hazel.
  • Week Thirty

    Week Thirty
    The fetus will now begin storing its own calcium, iron, and phosphorus. The fetus collects fat faster and faster and begins controling its body temperature.
  • Week Thirty One

    Week Thirty One
    At this point in the baby's development, almost all organs are developed and functioning, its digestive tract and lungs are very close to being mature, and its irises are now responsive to light.
  • Week Thirty Two

    Week Thirty Two
    The fetus will sleep most of the day at this time, and it will be less active due to lack of space. The head continues to grow larger in response to advancing of the brain.
  • Week Thirty Three

    Week Thirty Three
    The lanugo is disappearing and is being replaced by actual hair. All its fetus-fuzz is gone or almost gone.
  • Week Thirty Four

    Week Thirty Four
    The fetus will usually turn over around this time so its head it downward, to make birth easier. It will continue to grow larger.
  • Week Thirty Five

    Week Thirty Five
    The fetus is still storing fat to stay warm outside the womb and gaining weight in the process.
  • Week Thirty Six

    Week Thirty Six
    This week the fetus may drop into the birthing canal and is almost ready to enter the outside world. Contractions are known to start anywhere between this week and labor.
  • Week Thirty Seven

    Week Thirty Seven
    The fetus is ready to leave the womb, although it will be a few more weeks before the mother enter labor.
  • Week Thirty Eight

    Week Thirty Eight
    The fetus may have a full head of hair. The fetus will soon if not already make their first bowel movement.
  • Week Thirty Nine

    Week Thirty Nine
    The fetus has entered its final birthing position.
  • Week Forty

    Week Forty
    The due date has come and the baby is ready to be born. All organs are functional and matured.