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Fetal Development

  • Week 1

    Week 1
    The week of the last menstrual period.
  • Period: to

    Fetal Development

  • Week 2

    Week 2
    Ovulation occurs, the egg becomes fertilized, and the endometrium thickens to form a sac that will carry and cushion the baby.
  • Week 3

    Week 3
    Egg goes through cleavage (many divisions), it's set as a boy or girl based on the (X) or (Y) chromosome the sperm carries. The division occurs as it floats from the fallopian tube to the uterus.
  • Week 4

    Week 4
    Blastocyst: cluster of 50-60 cells (5-8 of embryo developed) through (IVF) the embryo is transferred into uterus, placenta attached to uterine wall, blastocyst releases (hCG) into bloodstream
  • Week 5

    Week 5
    Amniotic fluid builds up, embryo starts as 2mm, egg grows into the mucous membrane of uterus which covers egg, umbilical sac and amniotic fluid cavity, hole to uterus cavity is closed, placenta develops, and embryo recieves oxygen and nutrients.
  • Week 6

    Week 6
    Embryo 8mm, spinal cord closes, 1st blood cells and vessels develop, blood moves through primitive vessels, heart forms and beats, eyes start to develop, and cells for legs and arms are in place.
  • Week 7

    Week 7
    Embryo 15mm, heart beats with one chamber, division walls form in the heart, arm/leg buds grow, lower jaw/vocal chords begins to form, mouth opening formed, inner ear in process of being created, digestive tract developed, navel string created, and organs being formed: lungs, liver, pancreas, and thyroid gland.
  • Week 8

    Week 8
    18 mm, arms/legs grow (loc. of toes/elbows visible), feet/hand buds appear, face shaping, mouth/nostrils are developing, teeth develop under gums, and eyes can be seen as small hollows.
  • Week 9

    30 mm, fingers/toes defined (cartilage bones form), Body parts forming: upper lip, and tip of nose. Body parts developing: tongue, larynx, eyelids, and construction of heart complete
  • Week 10

    Week 10
    Fetus is the size of a strawberry. Developed body parts: jaws, mouth cavity, and nose is joined. Body parts forming: body muscles, nipples, hair follicles, and the baby begins moving.
  • Week 11

    Week 11
    CRL is 1.5 in, the toes and fingers seperate. Body parts developing: taste buds, testicles start to produce testerone if boy, has tooth buds, the whole body except the tongue is sensitive, and the cartilage is now calcifying to bone.
  • Week 12

    Week 12
    2.5 in, 0.7 oz, feet is 1/2 an in, face is more visual, pancreas produces insulin, finger nails and toes appear, and as a parent you can hear the baby's heart beat.
  • Week 13

    Week 13
    3 in, 1 oz, bone replaces cartilage and ribs appear, the nose and chin is defined, it can open and close its mouth, and the sex of the baby can possibly be figured out.
  • Week 14

    Week 14
    3 1/2 in, 1 1/2 oz, eyes move slowly to center of face, the nose is pronounced, ears fully developed, the cheek bones are visible, the 1st hair apppears, kidneys produce urine, If it's a girl ovaries move down to pelvis, and if it's a boy prostate gland develops.
  • Week 15

    Week 15
    4 in, 2.5 oz, the baby can move its arms and the baby's skin becomes thick
  • Week 16

    Week 16
    5 in, 3.5 oz, the fetus is covered with a protective to help regulate it's temperature, fat begins to form underneath the baby's skin, and the baby can hear, sleep, and dream.
  • Week 17

    Week 17
    5in, 5 oz, the umbilical thickens and becomes stronger, the retina is sensitive to light, and the 1st stools (meconium) begin to accumulate.
  • Week 18

    Week 18
    6in, 7oz, the baby can hear sounds, it can also recognize active/rest periods, and the skin builds a protective wax layer (vernix).
  • Week 19

    Week 19
    6.5 in, 9oz, placenta grows/ nourishes the baby, features of a baby's heart is visible, the baby's genital is recognizable, and the scalp hair continus to grow.
  • Week 20

    Week 20
    7in, 11 oz, can recognize mom's voice, mom feels first fetal movement, toenails/fingernails gorw, the growth for the rest of the body starts, skin gets thicker, and the heart can be heard.
  • Week 21

    10.5 in, 12.7 oz, the baby is gaining weight , and the fat is being added to the body, the bone marrow starts to make blood cells, and the small intestine starts to absorb sugars.
  • Week 22

    Week 22
    The fetus reacts to loud noises, has regular sleeping and waking rhythms, the mothers movements can wake the baby, taste buds are forming, 9 in long (450 grams)
  • Week 23

    Week 23
    11 in, 550 grams, eyebrows are visible, the baby can sucessfully suck its thumb, due to it's fully developed ear it can have a sense of it's position.
  • Week 24

    Week 24
    The baby is gaining about 3 oz a week, 1.3 lbs, 12 in long, eyelids can be seen, if it is born it is considered visable and the baby may be able to survive.
  • Week 25

    Week 25
    13 in, 1 1/2 lbs, bones become solid, hands fully developed, the baby's brain is growing rapidly, the brain cells are maturing,and the sexual organs are developed.
  • Week 26

    Week 26
    14 in, 1.7 lbs, feet is 2 in, hands are active, and the baby's eyes begin to open
  • Week 27

    Week 27
    14.5 in long, 2lbs, the baby's head is over 2.5 in, it's hearing continues to develop, the baby's eyes blink/open/ and close, and the appearance is much clearer
  • Week 28

    Week 28
    The baby has it's own intervals for sleeping and waking up, 14.8 in long, 2.5 lbs, the feet is over 2 in, the baby's hair is clearly visible, the milk teeth is developed, and the eyes are moving in the sockets.
  • Week 29

    Week 29
    15 in, 2.5 lbs, the brain is developing neurons, the baby's lungs/ muscles are maturing, the baby can taste and respond to pain.
  • Week 30

    Week 30
    16 in, 3lbs, head is about 3.5 in, feet is 2.5 in, the baby's wrinkled skin is becoming smoother, if it's a boy the testicles move to groin, and the baby controls it's temperature.
  • Week 31

    Week 31
    16.5 in, 3.5 lbs, the eyes are responding to light and darkness, and loud noises can cause it to jump
  • Week 32

    Week 32
    17 in, 4lbs, the head is 4 in, the underskin fat layer is getting thicker, the toenails/fingernails are completely formed, and testicles move from groin to scrotum.
  • Week 33

    Week 33
    17.5 in, 4.4 lbs, head is 8.5 cm long, lanugo is dissappearing, and half of the weight the mother is gaining is going towards the baby.
  • Week 34

    Week 34
    18 in, 5.25 lbs, the baby has an excellent chance of survival outside womb, and fat accumulations plumps up the arms and legs.
  • Week 35

    Week 35
    18.5 in long, 5.5 lbs, the baby's body is growing round due to the fat, baby's reflexes are coordinated, lungs are fully developed, and the baby has a 90% chance of surviving if born this week.
  • Week 36

    Week 36
    19 in, 6 lbs, the baby is becoming chubby, baby may gain an oz a day, and you as the mother may feel contractions.
  • Week 37

    Week 37
    19.5 in, 7lbs, head is 3.5 in, and the mother's water might break.
  • Week 38

    Week 38
    20 in, 7.5 lbs, the soft down is disappearing, putting on 1 oz a day, skin is "baby" smooth, the baby is reaching it's birth position, most babies come out head first, 3% come out feet first, and 1/8 th are caesaren.
  • Week 39

    20 in, 7.5lbs, has reached it's final birth position, cramped inside uterus, continues to punch and kick in the lower abdomen under pelvis, head is 4 in, and lanugo disappears.
  • Week 40

    Week 40
    Time to deliver, all systems are developed, the baby is 20in approximately, 7.5 lbs, contractions are starting, and it's time to deliver.