Fetal Development: Week by Week


4 Weeks Pregnant:

  • The brain and spinal cord begin to form
  • The heart begins to form
  • The stomach and intestines are forming
  • Bone tissue is growing
  • The eyes and ears are just beginning to form
  • The weight is less than one ounce
  • The length is less than 1/8 inch


6 Weeks Pregnant

  • The lungs are beginning to form
  • Brain activity can be recorded
  • Eyes are present, but no eyelids yet
  • The heart is more developed and is beating
  • Early reflexes develop
  • The hands and feet have fingers and toes, but may still be webbed
  • The length is less than 1/4 inch


8 Weeks Pregnant

  • All essential organs have begun to form
  • Elbows and toes are visible
  • The fingers are grown to the first joint
  • Facial features continue to develop – the eyes, nose, lips and tongue
  • The outer ears begin to take shape
  • Organs being to be controlled by brain
  • The length is about 1/2 to 3/4 inch


10 weeks Pregnant

  • The head is half the length of the body
  • The arms and legs and long and thin
  • The hands can make a fist with fingers
  • Red blood cells are produced
  • The length is about 1.25 to 1.75 inches


12 Weeks Pregnant

  • The neck is present and the face is well formed
  • Tooth buds appear
  • The arms and legs move
  • All body parts and organs are present
  • The fibers that carry pain to the brain are developed
  • Definitive signs of male or female gender are present
  • A heartbeat can be detected with electronic devices
  • The length is about 2 to 3 inches


14 Weeks Pregnant

  • The mouth makes sucking motions
  • Amniotic fluid is swallowed
  • Seat glands develop
  • The liver and the pancreas are starting to work
  • The length is about 3 to 4 inches


16 Weeks Pregnant

  • Swallowing and chest movements are clearly present
  • Movement may be felt by mother
  • The head and body become proportional
  • The neck takes shape
  • The weight is about 5 ounces
  • The length is about 4 to 5 inches


18 Weeks Pregnant

  • The fingernails are well formed
  • The unborn child can suck its thumb
  • Taste buds are present
  • Male and female gender is evident
  • The length is about 5 to 6 inches
  • The baby is about the size of a bell pepper


20 Weeks Pregnant

  • Eyebrows and eyelashes appear
  • Breathing like movements become regular and are detected by ultrasound
  • The unborn child turns its entire body side to side and front to back
  • The length is about 6 to 7 inches


22 Weeks Pregnant

  • Rapid brain growth continues
  • The eyes are fully functional and capable of movement
  • The vocal cords are active
  • Reflexes are present
  • The weight is about 1 pound
  • The length is about 7 to 8 inches


24 weeks pregnant

  • Unique footprints and fingerprints are present
  • Outside sounds can be heard
  • Actions such as hiccuping, squinting, smiling, and frowning may be seen through the ultrasound
  • The lungs have developed such that some premature babies may survive
  • The weight is 1 to 1.5 pounds
  • The length is 8 to 9 inches


26 Weeks pregnant

  • The eyelids open, close and can perceive light
  • The lungs have further matured and breathing is possible
  • The unborn child exercises muscles by kicking and stretching
  • The weight is about 1.5 to 2 inches
  • The length is about 9 to 10 inches


28 Weeks Pregnant

  • Brain-wave patterns resemble those of a full term baby
  • Another person can hear a heartbeat by listening to the pregnant woman’s abdomen
  • There is a good chance of survival if birth occurs at this stage of development
  • The weight is about 2 to 2.25 pounds
  • The length is about 10 to 13 inches


30 Weeks Pregnant

  • Rhythmic breathing movements occur
  • The bones are fully developed but still soft and pliable
  • The weight is about 2.5 to 3 pounds


33 Weeks Pregnant

  • Practicing skills to use outside the womb: swallowing, breathing, kicking, sucking
  • Accumulating more body fat
  • The weight is almost 4 pounds


36 weeks Pregnant

  • Fingernails have reached the tip of the finger
  • The weight is almost 6 pounds
  • The length is almost 20 inches


39 Weeks Pregnant

  • The baby is officially full term
  • The brain is growing at an astonishing rate
  • The baby is almost fully developed


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