Baby shadow

Fetal Development

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  • Week 1 (Start of first trimester)

    Week 1 (Start of first trimester)
    The last menstrual period. The start of the period is considered the starting point of the pregnancy.
    FUN FACT: Pregnancy lasts 266 days from the moment the egg is fertilized.
  • Week 2

    Week 2
    The endometrium within the uterus thickens. The ova and sperm meet in the fallopian tube and the resulting new embryo travels down to the uterus.
    FUN FACT: The ova is the largest cell in the human body.
  • Week 3

    The fertilized cell continues to divide itself. The fertilized egg is traveling down the fallopian tube.
    FUN FACT: The baby begins to form from this single fertilized egg.
  • Week 4

    The fertilized egg finally burrows into the lining of the uterus.
    FUN FACT: The baby's sex is predetermined by the father's sperm chromosomes.
  • Week 5

    Week 5
    The amniotic sac, amniotic cavity and yolk sac are developing. The placenta is also beginning to take shape.
    FUN FACT: At this time the embryo starts receiving oxygen and nutrition through the placenta.
  • Week 6

    Though not completely developed, all the major organs and systems are formed. The heart also begins to beat and can be detected as well.
    FUN FACT: At this time the embryo is still smaller than a raisin.
  • Week 7

    The embryo's major organs continue to form. Arms and legs begin to form as buds at each side.
    FUN FACT: The embryo is about 1/8 of an inch long.
  • Week 8

    The arms and legs continue to develope. The pituitary gland as well as the embryo's muscle fibers are beginning to form. The baby's facial features are now visible.
    FUN FACT: The embryo begins to practice movement (though not felt by mother till week 20).
  • Week 9

    The baby is now swimming round in a little bag of fluid. Head appears larger than the body because of rapid brain growth.
    FUN FACT: The baby is now about 1 inch long.
  • Week 10

    Week 10
    All of the organs, muscles, and nerves are in place and beginning to function. The unborn baby is now called a fetus.
    FUN FACT: Fingerprints are now evident on the fetus' skin.
  • Week 11

    The baby's face and brain continue to develope while the heart is almost completely developed and rsembles that of a newborn baby.
    FUN FACT: The fetus' whole bosy is sensitive to touch except the tongue.
  • Week 12

    The baby's heart can now be heard through a doppler monitor on the mother's tummy. The baby now has a chin, nose and facial profile.
    FUN FACT: The fetus can now suck his thumb and get hiccups.
  • Week 13

    The baby now produces insulin to control sugar levels and can move, flexing the arms and kicking the legs.
    FUN FACT: The baby weighs approximately 1 ounce at this time.
  • Week 14 (Start of second trimester)

    Hormones begin to take effect. Baby boys begin to develope the prostate gland and in baby girls, the ovaries shift down to the pelvis. The fetus continues to grow in size.
    FUN FACT: The kidneys are now producing urine.
  • Week 15

    Week 15
    Baby's skeletal system and senses are continuing to develope. The baby's taste buds are now formed.
    FUN FACT: The fetus' fingernails and toenails are now present.
  • Week 16

    The baby has now learned how to breath. These actions further stregthen and develope the lungs. More developed facial muscles lead to more facial expressions.
    FUN FACT: The fetus can now hear external noises, sleep and dream.
  • Week 17

    Fat under the baby's skin begins to develope. The skeleton is transforming from cartilage to bone (though it will remain flexible for birth).
    FUN FACT: The baby is about 5 inches long.
  • Week 18

    Vernix begins to form on skin to protect from months in water. The vocal chords as well as the alveoli in the lungs are formed. Baby now make crying out motions.
    FUN FACT: The baby now weighs 200 grams.
  • Week 19

    The fetus' genitals are distinct and recognizable. The legs are reaching a relative size and muscle development increases as well.
    FUN FACT: Scalp hair has spouted and continues to grow.
  • Week 20

    Week 20
    Sensory is now developing into their specialized area of the brain.
    FUN FACT: The baby can now hear and recognize its mothers voice.
  • Week 21

    The baby's bone marrow is now creating red blood cells. The baby is still steadily gaining fat.
    FUN FACT: Babys may respond to different types of music.
  • Week 22

    Th eyebrows and eyelids are fully developed and baby can hear conversation outside of the uterus.
    FUN FACT: The baby is now 11 inches long and weighs at about a pound.
  • Week 23

    Skin pigment is now forming. The baby is now proportioned like a newborn but thinner as they are still developing fat beneath the skin. The baby now has a sense of balance.
    FUN FACT: The fetus' eyebrows are now visible.
  • Week 24

    Lungs are developing branches of the respiratory tree. The body continues to fill out and the fetus looks more like a bormal newborn.
    FUN FACT: At this stage babies can be born and have a chance at surviving.
  • Week 25

    Week 25
    The fetus' hands are now fully developed and blood vessels within the lungs are developing.
    FUN FACT: The baby's sex organs are now fully developed.
  • Week 26

    The fetus' visual ans auditory systems are starting to develope.
    FUN FACT: The baby's eyes begin to open around this time.
  • Week 27 (Start of the third trimester)

    The baby's muscle tone is improving and fat is continuing to grow. The brain continues its rapid growth.
    FUN FACT: The fetus weighs almost 2 pounds.
  • Week 28

    Baby begins to dream during sleep.
    FUN FACT: The hair on the baby's head is now visible.
  • Week 29

    The brain continues to grow as well as develope. The baby is more aware of noises and tends to move a lot more often as the uterus gets cramped.
    FUN FACT: The fetus can taste and respond to pain.
  • Week 30

    Week 30
    The baby continues to gain weight and beins to cotrol its own temperature. Hands are now fully formed and can grasp things.
    FUN FACT: The baby now weighs about 3 pounds.
  • Week 31

    The baby's lungs and digestive tract are very close to maturity and now almost all of the major organ are functioning. Growth will focus on maturing organs, growing muscle mass, and storing fat.
    FUN FACT: The baby's eyes now open and repond to light.
  • Week 32

    The uterus becomes more cramped, and the baby's kicks seem less forceful. If the baby is a boy, his testicles are moving their way down to the scrotum.
    FUN FACT: The baby is now 17 inches long and weighs 4 pounds.
  • Week 33

    The baby is using it's lungs to practice breathing. The nails are as long as the tips of the fingers or longer.
    FUN FACT: The mother may gain a pound a week for the rest of the pregnancy.
  • Week 34

    The fetus has most likely turned to a head down position in preparation for birth. The baby is developing immunities to mild infections.
    FUN FACT: The child now has an excellent chance of survival outside the womb.
  • Week 35

    Week 35
    The fetus continues to gain fat. The lungs are almost fully developed, it's reflexes are coordinated, and respond to sounds, light and touch.
    FUN FACT: About 90% of babies born this week survive.
  • Week 36

    The baby continues to gain fat. The baby may drop into the birth canal in prepartion of labor.
    FUN FACT: The baby now weighs around 6 pounds.
  • Week 37

    The fetus continues to grow, stretch and squirm.
    FUN FACT: The baby now weighs about 7 pounds.
  • Week 38

    Developement is complete, the baby's main job now is to gain weight.
    FUN FACT: About one in eight births are caesarean.
  • Week 39

    Week 39
    The fetus' kicks no longerseem forceful.
    FUN FACT: The baby has reached its final birth position.
  • Week 40

    Week 40
    The fetus is ready for birth and is settling into the fetal position with its head down against the birth canal.
    FUN FACT: By now all systems are developed and ready to go.