original: The females have the unique ability to delay birth of their baby until their previous Joey has left the pouch.
simplifications: The females have the unique ability to postpone birth until their previous Joey has left the pouch. Females can delay birth until their previous Joey has left the pouch. The females have the ability to delay birth of their baby. The females can delay birth of their baby until their previous Joey has left the pouch. Females can delay the birth of their baby until their previous Joey has left the pouch. The females can delay the  birth of their baby until their last Joey has left the pouch. The females have a unique skill. They can stop their baby from being born until their previous child has left the pouch. Females are able to put off the birth of a baby until their previous baby leaves their pouch. Females can delay the baby's birth until the Joey has left the pouch. The females have the unique ability to delay birth of their baby until their previous offspring develops