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Timeline of normal fetal development
| Time (wk) | Development milestone |
|---|---|
| 4.5-5 | Appearance of gestational sac |
| 5-5.5 | Yolk sac becomes apparent |
| 6 | Embryo is seen, cardiac pulsation |
| 6.7-7 | Amniotic membrane appears |
| 7-8 | Appearance of fetal spine |
| 8 | Head and limbs begin to appear as distinct from torso |
| 8-8.5 | Fetal motion is appreciable |
| 8-10 | Rhombencephalon appears |
