Fair enough.  Pregnancy is a choice.  It requires close medical attention.  And it's managed effectively.

The military offers drug and alcohol rehab programs.  That lifestyle is a choice and requires a lot of treatment.

Last, to save on cost, they could always reclassify transgendered treatment as one not covered, similar to what they do with many cosmetic surgeries.  Leave it up to the person to decide whether they want to incur the cost on their own.