Correction

I was wrong about Le Metro not accomodating baby strollers. Almost all Paris metro stations have a pass-through gate like in NYC. Here, you put your ticket in the slot at the turnstile, walk over to the gate, and press a red button. A disembodied voice chimes in over a speakerbox: "Bonjour," and you fumble through something like "Pouvez vous abrir la puerta?" (It helps if you you mix a little Spanish in with your French).

You then cap it off with "J'ai du bebe a bord," a paraphrase of a car window sticker you saw a few minutes before entering the metro, and you'll hear the disembodied (and now somewhat bemused) voice say, "Je vous en pris," or some such, followed by a click of the lock. Pull the gate open and you're in.