Milestones of Fetal Development

pregnancy chart

  • Four Weeks
  • The embryo is 4 to 5 mm in length.
  • Foundations for nervous system, genitourinary system, skin, bones, and legs begin to form.
  • Rudiments of eyes, ears, and nose appear.
  • Five to Eight Weeks
  • The fetus is 27 to 31 mm in length and weighs 2 to 4 g.
  • Fetus is markedly bent.
  • Head is disproportionately large as a result of brain development.
  • Sex differentiation begins.
  • Centers of bone begin to ossify.
  • Nine to Twelve Weeks
  • The fetus average length is 50 to 87 mm and weight is 45 g.
  • Fingers and toes are distinct.
  • Placenta is complete.
  • Rudimentary kidneys secrete urine.
  • Fetal circulation is complete.
  • External genitalia show definite characteristics.
  • Thirteen to Sixteen weeks
  • The fetus is 94 to 140 mm in length and weighs 97 to 200 g.
  • Head is erect.
  • Lower limbs are well developed.
  • Coordinated limb movements are present.
  • Heartbeat is present.
  • Lanugo develops.
  • Nasal septum and palate close.
  • Fingerprints are set.
  • Seventeen to Twenty Weeks
  • The fetus is 150 to 190 mm in length and weighs approximately 260 to 460 g.
  • Lanugo covers the entire body.
  • Fetal movements are felt by woman.
  • Eyebrows and scalp hair are present.
  • Twenty-one to Twenty-five Weeks
  • The fetus is about 200 to 240 mm in length and weighs 495 to 910 g.
  • Skin appears wrinkled and pink to red.
  • Eyebrows and fingernails develop.
  • Sustained weight gain occurs.
  • Twenty-six to Twenty-nine Weeks
  • The fetus is 250 to 275 mm in length and weighs about 910 to 1,500 g.
  • Skin is red.
  • Rhythmic breathing movements occur.
  • Pupillary membrane disappears from eyes.
  • The fetus often survives if born prematurely.
  • Thirty to Thirty-four Weeks
  • The fetus is 280 to 320 mm in length and weighs 1,700 to 2,500 g.
  • Toenails become visible.
  • Eyelids open.
  • Steady weight gain occurs.
  • Vigorous fetal movement occurs.
  • Thirty-five to Thirty-seven Weeks
  • The fetus average length is 330 to 360 mm: weight is about 2,700 to 3,400 g.
  • Face and body have a loose wrinkled appearance because of subcutaneous fat deposit.
  • Body is usually plump.
  • Lanugo disappears.
  • Nails reach fingertip edge.
  • Amniotic fluid decreases.
  • Thirty-eight weeks (full term)
  • The average fetus is 360 mm in length and weighs 3,400 to 3,600 g.
  • Skin is smooth.
  • Chest is prominent.
  • Eyes are uniformly slate colored.
  • Bones of skull are ossified and nearly together at sutures.
  • Testes are in scrotum.

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