Surprised that no one has mentioned this, but I also nannied for twin premies (born at around 25 weeks like you mention these babies were) and for the first year it's advised you keep them at home unless absolutely necessary. I only ever went out with them if they had a doctors appt. and MB needed a hand caring for both babies (they were a handful!). Otherwise we stayed home. Taking them out for a 2 hour stroll in the cold would have been unthinkable to all of us, because even if the babies were healthy now, their immune system is quite weak, and we didn't want to put them in any sort of compromising situations.

So yes, casually tell this mother. You don't have to sound accusatory, just tell her something along the lines of "Wow, I saw your nanny taking quite a long walk yesterday, those babies must really love their stroller!" and if she already knows about this, it will be no big deal, but if she doesn't she now has the information.

As a mom, if someone thinks something is not quite right with my nanny, I'd want to know. Even if there was no issue whatsoever. I'm not at home with my kids, and other people are the best resources, particularly in the early days. Once at the park, I was on the phone with our nanny and a mom yelled at her that she was going to tell her boss on her and my nanny said "ok, she's on the phone, want to talk with her." It was pretty funny, but I know that the mom was well intentioned.

Ok, if you've convinced yourself that you should myob, could you go up to the mom and say something like "your nanny has so much energy! Those walks she goes in are amazing! Its a good 3 hours round trip, I think and sonetimes, I see her twice a day! Your little ones must live the stroller - mind never did/mine did, too"

Youve now opened the door for her to question you if she finds the information alarming and let her off the hook by praising the nanny first.

OP here - I really don't think you all are understanding. There is no place she is going to. I initially thought that was what she was doing. But then I realized she really is just walking. It is not hard to notice things. She does not have a diaper bag with her. Never has bags or other things with her. When I stopped her one of the babies was awake. One was sleeping. I seriously doubt that the 12 lb babies are going to the playground. And yes, it is possible that she stopped at someone's house for a playdate....I really don't know. But given what I have seen these past several months it really is not likely. I am not following her, but I am in and out of the house all day so I can see these things.

I think this is the most important point. If you aren't a crazy stalker, then you aren't keeping a 24/7 eye on her, and, as such, you don't know.

Honestly, I think this a fake post because I have a hard time believing you have such an abundance of free time that you would be able to know what someone else was doing every minute of the day. That said, if you aren't fake, you are kind of creepy. Why on earth are you so concerned with someone else's kids, especially when the great crime you are concerned with is...walking too long?

Are you sure she's not taking them somewhere??

8:18 here. I will caveat this to say that perhaps it's different for twins but sleeping in the stroller for most naps is not good either, if that is what's going on. Now if MB has requested it then fine - that's her issue. But why in the world would you NOT mention something to the MB in case it's not at all what she wants for her kids??? It's not widgets we're talking about here - it is young children who cannot speak for themselves and whose formative years are being spent either in good care or poor care.