Fattened up on bites of potatoes, yucca and chicken starting at 4 months, some of the babies wearing sporty clothes and frilly dresses are rolly-polly chubby. As striking as their sizable girth are their heads, beautifully round and fully formed with none of the deep skin folds that corroborate the Zika virus' devastating ability to halt normal brain expansion as infants develop in utero.