Postive outcome after TFMR?

hi, just looking to see if anyone has been in a similar situation. Last year i had a TFMR at 15weeks (feb 2020) our baby was diagnosed with anencephaly. i had an amnio and everything came back clear and we were told that unfortunately sometimes this things just happen and are random. We were told to take an increased dose of folic acid for any future pregnancies but the chance of anything similar happening again was very slim. i started the higher dose of folic acid in the march. Fast forward to November and we are pregnant again and everything seems to be going fine until our 20 week scan where baby was diagnosed with severe spina bifida. Devastated we had to go through a TFMR again. This time we asked if there would be more investigation as to why this has happened and decided to have a Post mortem done. Anencephaly and spina bifida are not the same but both stem from the neural tube. We have an appointment with the consultant for the PM results on Thursday and are just dreading being told there is something else going on that could cause this or prevent any future pregnancies. We have an almost 3 year old already and he is perfectly fine and had a great pregnancy with no issues. Just looking to find out if any one has had similar reasons for losses and has gone on to have a healthy baby after? TIA x