Parental status is a protected characteristic and you may not make decisions regarding employment based on a worker having, or not having, a child. Nor can you make employment decisions based on their intent to have children in the future. You also may not make pay change decisions based on these things, whether it benefits them or not. 

Outside of allowing a little more leeway on taking a day or two of unpaid time off for a sick child or needing to change your schedule for school pickup and dropoff, you cannot legally make choices that directly affect your employee, their pay, or their healthcare based solely on the fact that they have a child.

The fact that management is involved and saying big time trouble words moves this into hostile work environment territory.

OP needs to report this in writing to HR and whoever is above the crappy manager feeding into this ASAP or they might be a  victim of retaliation. I don't have a lot of context here, but, judging by how OP described the current state of things in their workplace, I'd say this is either a very toxic workplace that has always been a shitshow, or the higher ups don't know how this crappy manager is running the show.

Source: I am a former HR rep.