I was IVF ISCI FET too. I understand where you are coming from, the pregnancy is hard fought, and all the waiting around is hard. All you can do is eat your folic acid and know you're doing all you can; instead of worrying about it I spent my efforts reading up on what could go wrong at which stage and planning contingencies. My husband thinks I'm morbid but I feel having a roadmap helps.
If it gives any comfort I'm 35yo and W28 now, and so far there hasn't been any abnormalies sighted. In the early months the baby is bigger than normal and the gynae advised may have to C-sect, but he has since gotten back into range it seems.