Check for a small white bullseye or ring on the yolk called the germinal disc
Look for visible blood vessels after a few days of incubation
Candle the egg with a bright light in a dark room
Watch for embryo development during incubation
Observe movement inside the egg after several days
Check whether the hen has been with a rooster before the egg was laid
Crack the egg open and look for a bullseye-shaped germ spot on the yolk
Use incubation time and temperature to confirm development
Consult a veterinarian or poultry expert if unsure