If a profile has baptism dates but no data has been entered in the birth fields nothing will show up on the profile page.
As the is now a "Before" option for each date field the data from the baptism field could be automatically place into the Birth field with the caveat that the "Before" would be toggled (and only if the birth date field is blank).
I realise that some religions dont baptise until adulthood but the statement "XYZ was born before ABC date" would still be correct regardless of the persons age at ABC.