The more you use an app, the more space the app takes up on your phone. So if you use oogababy more than other apps, it's likely it will take up more space on your phone than apps you don't use as often. However, your phone automatically resets the storage space an app uses every week, so you don't need to worry about storage for any app becoming increasingly larger over time.
If you want to manually decrease the amount of space oogababy takes up, you can delete and reinstall the app (your moments + profile data will be saved).
On iOS, you can find out how much space oogababy takes up on your device by opening the Settings app and tapping General > Usage and finding oogababy in the Storage section.