Tashy my dd1 had this diagnosed at 20wk scan, they were very worried about it and discussed worst case scenario, I had an amnio and mri on bubs, all came back clear. As she got bigger it started to resolve and by 36 weeks was almost normal. But......DD has a genetic condition called 1p36 deletion syndrome, and the enlarged ventricals are one of the indicators, but her syndrome doesn't get tested on a standard amnio.