Fetal development

• • Spinal cord is formed
  • Arms and legs are bud-like structures; rudimentary eyes, ears, and nose are discernible
  • Wt: 400 mg; length 0.75 cm

  4 weeks
• • Organogenesis complete
  • Every organ system is present
  • Heart beats rhythmically
  • A sonogram shows gestational sac
  • Wt: 20 g; length 2.5 cm

  8 weeks
• • Bone ossification centers begin to form
  • Tooth buds are present
  • Kidneys begin to form urine
  • Fetal heart rate is audible by Doppler (FHR 110-160 beats/min)
  • Wt:45 g; length 7 to 8 cm

  12 weeks
• • Sex can be determined by ultrasonography
  • Amniotic fluid is 200 ml (amniocentesisis 14-16 weeks)
  • Lanugo is well-formed
  • Liver and pancreas functioning
  • FHR is audible by an ordinary stethoscope
  • Wt: 55 to 120 g; length 10-17 cm

  16 weeks
• • Spontaneous movement felt by the mother (quickening)
  • Hair growth on eyelashes, and brow
  • Passive antibody transfer from the mother
  • Definite sleeping and activity patterns are distinguishable
  • Wt: 223 g; length 25 cm

  20 weeks
• • Meconium is present
  • Lung surfactant present
  • Hearing present
  • Age of viability
  • Wt: 550 g; length: 28 to 36 cm

  24 weeks
• • Lung alveoli are almost mature
  • If born, newborn can breathe at this time
  • Wt: 1,200 g; length 35 to 38 cm

  28 weeks
• • Subcutaneous fat begins to be deposited
  • Iron stores beginning to be built
  • Wt: 1,600 g; 38 to 43 cm

  32 weeks
• • Additional amounts of subcutaneous fat are deposited
  • Lanugo disappears
  • Vernix increases
  • Testes palpable in scortum
  • Wt: 1,800 to 2,700 g; length 42 to 48 cm

  36 weeks
• • Fetus kicks actively
  • Fetal hemoglobin to adult hemoglobin
  • Sole creases cover the feet at least 2/3
  • Lightening occurs
  • Wt: 3,000 g; length 48 to 52 cm

  40 weeks