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Fetal Development Timeline

  • Conception: Egg to Embryo

    This is the process of the sperm fertilizing the egg.
  • Ovulation

    Every month, both ovaries in a woman's body release a mature egg.
  • Moving to the Fallopian Tube

    The egg releases to be fertilized by a single sperm in the Fallopian tube.
  • Fertilization: Sperm Penetrates Egg

    Once the sperm makes it's way to the egg and penetrates it, the egg surface will change to prevent another sperm from coming in. This is when the genetic makeup happens and determines the gender.
  • The Cells Start to Divide

    This is when the rapid process of division begins after the egg is fertilized.
  • Implantation

    This is when the fertilized egg attaches to the lining tissues of the uterus. The cells still continue to divide.
  • Pregnancy Hormones

    The cells produce HCG and it eventually forms the placenta. This is when the woman can start taking pregnancy tests.
  • Fetal Development

    You can now call the baby a fetus. There is already a heartbeat and the baby is already about a 1/2 inch long.
  • Week 6

    You can now detect a heartbeat during an ultrasound. The baby's heart and brain begin to develop.
  • Week 7

    The baby's spinal cord and backbone begin to develop. Also, the amniotic sac and fluid are forming. This is to protect and provide cushioning for your baby. Also, the genitals begin to develop.
  • Week 8

    This is the end of the second month of pregnancy. The baby's eyes are starting to form.the baby's bone starts to replace cartilage. The digestive tract and sensory organs begin to develop.
  • Week 9

    Buds for the baby's future teeth start to appear. The baby's fingers and toes begin to form. The bones and muscles continue to grow.
  • Week 10

    The baby's intestines begin to start forming. Also, the backbone is soft and can flex.
  • Week 11

    At this time, the hands are more developed than the feet. The legs are shorter than the arms, but it won't stay this way.
  • Week 12

    The baby is fully formed. It can open and close its fists and mouth. Also, external ears start to form.
  • Week 13

    This is the beginning of the fourth month of pregnancy. The baby's arms and legs can now start to flex.
  • Week 14

    The baby's external sex organs are fully developed. The outer ears can now be seen.
  • Week 16

    The fetus can now swallow and hear. The neck is formed. Also, the kidneys start to function by producing urine.
  • Week 17

    This is the beginning of the fifth month of pregnancy. If the baby's hand happens to float to the mouth, it might start to suck on it's thumb. The baby's skin is wrinkled and it's skin is coated with vernix and fine hair.
  • Week 18

    The fetus is starting to become more active and the mother can feel it move. The baby begins to have a sleeping routine.
  • Week 19

    The baby's fingertips start to grow nails. Also, to be able to digest nutrients, the baby's gallbladder begins to produce bile.
  • Week 20

    This is the end of the fifth month. If the baby is a girl, her eggs have formed in the ovaries. If the baby is a boy, his testicles have began to form downwards. This is when the mother can use an ultrasound to determine her babies gender.
  • Week 21

    Mothers may start to feel their baby hiccup. The baby's brain is rapidly developing.
  • Week 22

    The baby is now about a foot long and is close to two pounds. Tear products begin to develop.
  • Week 23

    The baby's finger and toe prints are now set in place. It's skin is translucent and you can see the baby's veins though the skin.
  • Week 24

    This is the end of six months. Although the lungs are fully formed, they are not yet ready to work outside of the uterus. The baby's eyelids begin to part and it's eyes start to open.
  • Week 25

    The baby can sense changes in light and also open and close it's eyes. It starts to stay in a curled up position where it's arms and legs are crossed.
  • Week 26

    The baby kicks and stretches on a daily basis. If the mother went into premature labor, the baby would have a chance of surviving because it's lungs are now capable of breathing air.
  • Week 27

    The baby can respond to sounds and it's hearing is fully developed. Grasping motions can now be made by the baby.
  • Week 28

    Fat begins to form on the baby, giving it those cute chubby cheeks. The baby's lung cells make a substance that enables breathing.
  • Week 29

    Lanugo begins to fall off the baby. Major developments are finishing up, so the baby starts to gain weight very fast.
  • Week 30

    The fetus's bones start to harden and become strong. The skull stays soft though for birth.
  • Week 31

    There are many regions in the brain, not all of them are formed though, but they continue to grow. The baby weighs about four pounds.
  • Week 32

    This is the last week of the eighth month. The baby's hair starts to grow on its head. If the mother hasn't already, she will start to experience Braxton Hicks contractions.
  • Week 33

    This is when the process of the baby turning its head downwards starts to occur. During this month, the baby's brain continues to develop.
  • Week 34

    The baby's respiratory system is still developing. Also, its skin starts to lose the wrinkles.
  • Week 35

    Although the lungs can function outside of the uterus, they still continue to grow and develop fully. The baby is practicing for its first breath. It does this by inhaling amniotic fluid
  • Week 36

    The baby starts to develop sleeping patterns. Contractions will happen more often and make the mother think that she is going into labor, even though she isn't.
  • Week 37

    The fetus begins to drop even lower in the pelvis. The baby learns to grab and uses the umbilical cord to become more coordinated.
  • Week 38

    Even more fat forms on the baby. This happens in places such as the elbows, knees, and shoulders. The baby's brain and lungs are almost 100% ready to work outside of the uterus.
  • Week 39

    During this last month of pregnancy, the baby gains about 1/2 a pound per week. The mother will feel a lot of cramping and tightening in her pelvic area.
  • Week 40: Birth

    Today is the day! The mother's cervix prepares by stretching and thinning out. This opens up the cervix so that when it is time for the baby to finally come out, it will fit.