Yes true almost all the main FLs go through miscarriage once, it's itvs norm, from Og Akshara to Naira to Ishita to Archana, Purvi to Og Simar and many more, everyone went through miscarriage, So I'm not surprised that Sai is having miscarriage, also even technically it quite an early to bring pregnancy for Sairat, generally FLs become pregnant when show is about to take leap and story will eventually shift to leads' kid in maximum 2-3 months.
Here it's not the case, they will drag and drag till the time they can with these three, hence Sairat kid is not coming anytime soon as per me.
Right now I think Sai will miscarry but they will not declare her as infertile coz it'll close all ways of future pregnancy, makers will again make her pregnant when the separation or a probable leap is round the corner, till then all sorts of nonsense will be showed down.