Gravid Spot

• All female guppies have a "gravid" spot on the belly, but a pregnant guppy's gravid spot will be very dark.
  
  

Belly Size

• Like pregnant women, pregnant female guppies' bellies grow larger as the pregnancy progresses.
  
  

Belly Shape

• Looking straight on, a pregnant guppy's belly looks like cube.
  
  

Skin Pattern

• If you see tiny black spots on or below a female guppy's tail, she is pregnant and close to delivering her fry.
  
  

Activity Level

• When a pregnant guppy is near the end of her 4-week pregnancy, and she is ready to deliver her baby guppies, she becomes less active or stops swimming completely.