It's the smugness, and the fact that Maaaawk doesn't know about neck so he never warns her to extend hers when he's about to take another shot with hisVery mean for saying this! I have never found pregnant women unattractive, even when Lily pull off the miserable toilet hugging face, I found her okay.
I cannot say the same with Anna, even when she looks happy, she just looks like bland unseasoned potato