Waa-waa. These embarrassing goofs on Yahoo! Style make me cry.
Ms. Missoni is pregnant with baby number two, meaning she’s having one baby, which is a bambino. The word bambino, which is now considered informal English, is singular; bambini (or bambinos) is the plural.
So this genius of a writer uses a plural when she needs a singular and then uses a possessive when she needs a plural. I know I don’t have to tell you this, but I will anyway: The plural of baby is babies. Anything else is just the result of gross ignorance.