Hi OP, sorry I'm a bit late to the chat and apologies for the essay....
My daughter was born with a complete unilateral cleft lip and palate - she's just turned 4. I'm a regular volunteer with CLAPA and I help to facilitate the antenatal support groups for families with a recent diagnosis so I do have a decent bit of experience in the area.
There was no history of cleft in my family and it was a complete shock to us at my 20 week scan. Like you, I was absolutely sick with guilt at how I might have caused it despite doing everything "properly" to the letter. The fact is, nobody will ever be able to tell you and I how your baby's cleft might have occurred (unless there's a clear genetic link in your family) so please try and make peace with yourself in the knowledge that it is incredibly unlikely that anything that you did might have caused this, and that knowing how the cleft has occurred ultimately wouldn't change anything anyway. The care pathway is the same regardless.
I cried for weeks post-diagnosis, refused to engaged properly with my pregnancy out of anger at the situation and, once I felt ready to, I reached out to CLAPA and spoke with a parent-peer counsellor who was amazing. I'd strongly recommend doing this. The antenatal support groups are fab - they're always attended by a cleft nurse specialist from one of the regional teams who can help to answer specific questions and it's a great way to start the journey. I've seen families cry many a tear at the groups and I've cried with them - it's a very safe space.
Cleft palates are generally more common in complete cleft lips so there is the chance your baby's palate will be unaffected. It's incredibly difficult for a sonographer to see a cleft palate on an ultrasound so whoever you ask, you're likely to be told that you won't know until they're born and assessed. I was heartbroken that I couldn't directly breastfeed but I got on with feeding with expressed milk and harvested colostrum just fine as I felt it was the next best thing I could do. I still consider my child to have been breastfed! We never had a moment's concern feeding. It's likely that they'll pop a feeding tube in for the baby as soon as they're born just as a failsafe to be able to get some milk into them in case of difficulty. My daughter was fitted with a tube and as soon as she'd been assessed by our cleft nurse specialist (less than 24 hours after birth) the tube came straight out and she was on a bottle - and this is with a considerable cleft palate. She never needed the tube, it was just in-case.
I completely understand your fears about other peoples' judgments and I spent many an hour having imaginary arguments in my head with people so that I had responses prepared just in case. Hand on my heart, people only ever looked at my baby with love and never once made a cruel comment or looked at her "funny". You will be so fiercely proud of your baby that you'll almost will someone to test you. A young lady approached me at a local adventure playground very recently who had been born with a cleft herself and she noticed that my daughter had been too. The lady told me that my daughter's confidence is amazing and that she will be an absolute star growing up. The lady herself had been born with a complete bilateral cleft and was very affected. She's beautiful, glamorous, very fashionable, eloquent and intelligent, set to get married next year and was there with her own daughter who is not cleft-affected. She was happy to tell me that she'd never been bullied, had always felt confident in herself and she could see my daughter heading in the same direction. I was so very proud I cried on the spot. Your attitude will matter so much so let that love and pride shine through once the fear subsides. My daughter's lip repair is incredible and most people would never know any different - so much so that I tell anyone who will listen that she was born with a cleft because I am proud. It doesn't define my child but it is part of her story. We bought a specially customised teddy for my daughter which had a cleft scar sewn onto it on the same side as her cleft and it was there with her the day she was born.
Honestly the fact that you are even worried about the prospect of letting your baby down shows what a great parent you're about to be. With a few years' parenting under my belt I can tell you that I've let my child down in a few ways (gave her the wrong pizza, short-cut a bedtime story after a long day, threw away a beloved broken toy, etc) but I have come to know that I have never let her down when it has come to her cleft or how I could have caused it, and neither will you.
After her surgeries, pain management has been excellent and I have seen my second-born son in infinitely worse states with colds, coughs and bugs than I ever saw my daughter in post-surgery. All of it is hardest on your heart as a parent in my honest opinion. If it helps, I came so full circle from my fears during pregnancy that I happily and proudly volunteer with CLAPA now, so if I can be any sort of indication of what you have to come, I would like to reassure you that you're not alone with your feelings and that you're still a parent just like any other. I don't see myself as a "cleft mum". I'm just a mum of a child who happened to be born with a cleft. I get sass and attitude just like anyone else from a child who we thought would never be able to speak "properly". How wrong we were!
If you would like to chat further, please feel free to send me a direct message. Happy to connect and answer any questions or be a safe place for you to share any thoughts. Be kind to yourself and good luck with the rest of your pregnancy! x