Unless their under 12 wks I would go by calendar months, but thats just me. I know the MCHN (oooo I have to make paris' next appt...thanks for the reminder) Goes by weeks up until 3 mths and then by months going by their birthdate. Does that make sense? So if it were me I would say 7 mths and 3 weeks

*hugs*
Cailin