It's all down to smoking, drinking, not taking folic acid, eating sushi, taking medication and it's hereditary....X In actual fact, it seems like no-one has a specific answer.
I have spoken with other mothers who have children with clefts who have unfortunately been made to feel it was something THEY did that caused the condition. They had been questioned if they had been taking their folic acid in time, been made to feel bad that they may have drunk alcohol during pregnancy before they knew they were pregnant and heaven forbid they'd eaten sushi in early days of pregnancy. I think I 'got lucky' in that respect because having a cleft already, it was more about tackling the guilt that I felt for passing it on (the chances of me passing it on was between 2-8%...)
Real talk. NO-ONE IS TO BLAME. You can't foresee it happening and you can't stop it from happening either.
If you are worried, anxious or feeling guilty about the diagnosis, my best advice would be TALK. Talk to your friends, talk to your family or even your Cleft Nurse about how your feeling. Also, speak up if you feel someone has made you feel responsible for the condition - especially those in a healthcare setting.