The Collaborative International Dictionary of English v.0.48:

Catamenial \Cat`a*me"ni*al\ (k[a^]t`[.a]*m[=e]"n[i^]*al), a.
   [Gr. katamh`nios monthly; kata` down, back, again + mh`n
   month.]
   Pertaining to the catamenia, or menstrual discharges.
   [1913 Webster]

WordNet (r) 3.0 (2006):

catamenial
    adj 1: of or relating to menstruation or the menses; "menstrual
           period" [syn: menstrual, catamenial]