Because their white color indicates fertilization, you can expect them to shift position in the saddle to the area behind the rear legs as they get bigger.
A female ghost shrimp will continue to fan the legs that carry the eggs if she is pregnant.
It is unclear why pregnant female ghost shrimp fan their legs. It could have to do with ensuring adequate oxygen supply to the eggs, or it could be a response to the eggs' irritability.
Are Turtles Lucky or Unlucky?