From StandTrue.com:
20 days: Foundations of brain, spinal cord and nervous system are laid.
24 days: Heart begins to beat.
30 days: Child has grown 10,000 times to 6-7 mm (1/4″) long. Brain has human proportions. Blood flows in veins (but stays separate from mother’s blood).
35 days: Pituitary gland in brain is forming. Mouth, ears and nose are taking shape.
42 days: Skeleton is formed. Brain coordinates movement of muscles and organs. Reflex responses have begun. Penis is forming in boys. (Mother misses second period.)
43 days: Brain waves can be recorded.
8 1/2 weeks: Fingerprints are being engraved. Eyelids and palms of hands are sensitive to touch.
9 weeks: Child will bend fingers around an object placed in the palm. Thumb sucking occurs. Fingernails are now forming.
10 weeks: Body is sensitive to touch. Child squints, swallows, puckers up brow and frowns.
11 weeks: Baby urinates, makes complex facial expressions – even smiles.
12 weeks: Vigorous activity shows distinct individuality. Child can kick, turn feet, curl and fan toes, make a fist, move thumbs, bend wrists, turn head, open mouth and press lips tightly together. Breathing is practiced.
13 weeks: Face is prettier, facial expressions resembling parents’. Movements are graceful, reflexes vigorous. Vocal chords are formed (but without air baby cannot cry). Sex organs are apparent.
4 months: Child can grasp with hands, swim and turn somersaults.
5 months: Sleeping habits appear, but a slammed door will provoke activity. Child responds to sounds in frequencies too high or low for adults to hear.
6 months: Fine hair grows on eye brows & head. Eye-lash fringe appears. Weight is about 640g (22 oz.), height 23 cm (9″). Babies born at this age have survived.
7 months: Eye teeth are present. Eyelids open and close, eyes look around. Hands grip strongly. Mother’s voice is heard and recognized.
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Hat Tip — Pieter Friedrich