Officially no, however needing frequent stretch breaks and trips to the lav could fall under 'medical preboard'.

An A or B boarding pass, with T-24hr checkin, EBCI fee, or gate boarding upgrade to A1-15 fee would also have near certain success of getting an aisle seat.​

//I don't want to start any debate, but if by chance your wife and her medical providers have recommended making when traveling (hepa filters do not run effectively during during boarding/taxiing), boarding with a late A/early B boarding pass also has the benefit of helping you choose your nearby seatmates....