Theoretically, it is possible that diphenhydramine could affect a woman's milk supply, since the medication can suppress prolactin (a hormone important for breast milk production). However, this is probably not an issue for women who are well-established with breastfeeding.
PRO is a strategic communications firm helping high profile individuals, professional teams, national governing bodies, corporations and non-profits within the sports industry build their brands through the media.
Pro is not an abbreviation, but 'con' is for 'contra.' From the OED: An argument or consideration in favour of something; reasoning in support of a proposition, thesis, etc.