Fetal Development Timeline

  • Week 1

    Week 1
    The first week of pregnancy starts from the first day after someone's last menstrual period. Pregnancy usually lasts from 38-42 weeks.
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    First Trimester

  • Week 2

    Week 2
    After the egg has been fertilized a sperm, it starts a rapid cell division and travels up to the uterus. The combination of the egg and the sperm's chromosomes determines the baby's sex and physical characteristics.
  • Week 3

    Week 3
    After fertilization of an egg, all of the DNA needed to make it human are present. The cells continue rapid cell division as it travels from the fallopian tubes through the uterus and embeds itself into the uterus' lining.
  • Week 4

    Week 4
    The fertilized egg, also known as a blastocyst, implants itself to the uterine wall where it releases hCG, a hormone used for detecting pregnancy. The rapid increase of hCG levels produces the symptoms for pregnancy.
  • Week 5

    Week 5
    The blastocyst multiplies quickly and divides into the placenta and the baby. By the end of the week, the baby's spinal cord and brain starts to form.
  • Week 6

    Week 6
    The mother can become extremely tired because of the rapid development of the baby. The baby's heart starts beating, its brain divides into five parts and their optic pits form.
  • Week 7

    Week 7
    The baby's lungs, liver, mouth, ear, vocal cords, limbs, and other major organs are developing.
  • Week 8

    Week 8
    The baby's limbs continue to grow and it starts to move. Its facial features are visible and the mother goes to her first prenatal visit.
  • Week 9

    Week 9
    The head appears larger than the rest of its body because of the rapid delevopment of the brain. The fingers and toes become more noticable and cartilage begin to form.
  • Week 10

    Week 10
    It's now called the fetus and they're about the size of an inch. Their fingerprints are now visible, and their hair follicles begin to form.
  • Week 11

    Week 11
    The fetus' reproductive organs and tooth buds begin to form and cartilage starts to become bones. Its neurons multiply, totaling to about 250,000 a minute.
  • Week 12

    Week 12
    Its pancreas produces insulin and nails starts to form. They start to move a lot.
  • Week 13

    Week 13
    The fetus can flex their limbs, open and close its mouth, and suck its thumb.
  • Week 14

    Week 14
    The baby starts to pee in the amniotic fluid, and they become covered with very fine hair to protect them from the fluid they currently live in.
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    Second Trimester

  • Week 15

    Week 15
    The head and the body is more proportional, bones and muscle continue to grow, and they can now taste. Some mothers may feel the movement of the fetus.
  • Week 16

    Week 16
    Facial expressions are noticable. They can hear voices, sleep, breathe and kick around.
  • Week 17

    Week 17
    The baby is about 5 ounces and 9 inches in length. They develop fat under their skin to help keep them warm, and they start to poop.
  • Week 18

    Week 18
    Vernix forms on the baby's skin to protect them from the water. They hear sounds, sleep and even dream.
  • Week 19

    Week 19
    The baby's genitals can be recognized, and their hair continues to grow.
  • Week 20

    Week 20
    It can now recognize different voices. Their heartbeat can be heard and, the mother can feel its movements.
  • Week 21

    Week 21
    The baby starts producing its own blood cells and absorbing sugar.
  • Week 22

    Week 22
    The fetus has a regular sleep-wake cycle, and their taste buds start to form.
  • Week 23

    Week 23
    They may know their different positions. Their pancreas continues to grow and now produces their own insulin.
  • Week 24

    Week 24
    They start to breath more as they inhale and exhale the amniotic fluids. They have a 36% chance of survival if they are born now.
  • Week 25

    Week 25
    They explore their living quarters using their fully developed hands. The parts of the spine form, brain cells start to mature, and their sex organs become fully developed.
  • Week 26

    Week 26
    The eyes start to open. They become really active and are sensitive to touch.
  • Week 27

    Week 27
    It can open its eyes and blink. Its hairs continue to grow and muscle continues to develop.
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    Third Trimester

  • Week 28

    Week 28
    They can recognize the mother's voice and respond to it when heard. They can dream.
  • Week 29

    Week 29
    They can taste, feel pain and follow the light. Their movements lessen because of the increasing amount of space they take up.
  • Week 30

    Week 30
    They baby gains weight, produce its own red blood cells, have smoother skin, and control its own temperature.
  • Week 31

    Week 31
    Its major organs starts maturing. Their eyes can fully open and respond to the light and darkness.
  • Week 32

    Week 32
    The baby has a lot less movement, and their reproductive organs continue to develop.
  • Week 33

    Week 33
    The baby drinks and pee constantly. The mother will gain pounds that will go towards her and her baby.
  • Week 34

    Week 34
    The baby is about 18 inches in length and weighs five and a quarter pounds. They gain a lot of fat in their limbs.
  • Week 35

    Week 35
    They continue to gather fat under their skin and have reflexes.
  • Week 36

    Week 36
    They continue to get fatter and may position themselves into the birth canal.
  • Week 37

    Week 37
    The mother is considered ready to give birth and may often experience vaginal discharge.
  • Week 38

    Week 38
    The baby continues to gain weight and eat up most of the fluids in their current home.
  • Week 39

    Week 39
    There is very little movement in the belly, and the lanugo that covers the baby is gone.
  • Week 40

    Week 40
    The baby is ready to come out into the world at any second. It's normal for the mother to become very sensitive around this time.