Leave the Kids out of This
There are a few things that you just shouldn’t say to people, at least within a lot of cultures: “You’ve put on weight,” is one that springs to mind, or its distant cousin, “So when’s the baby due?” These are basic unwritten rules that people should just know.
And a big one, I would say, is “Your baby is not cute.” First off, babies are all cute in their way; even if a baby has a little gremlin face, there’s something about them being so tiny and snuggly that makes them all adorable, no matter what their face looks like. Secondly, why would you say that within hearing of the mother? You might think that baby has an ugly face, but behavior like that is what’s truly ugly. Keep your thought to yourself.