Complicated Situation

My girl is missing an ovary. I'm in a step parent situation and she found out she's missing an ovary and fallopian tube when they had to surgically take her first born out. I then assumed it was a 50% chance each try. My doctor said the pattern doesn't work like that. One ovary could release twice in a row or not release three months in a row. There is no way to tell which month to go for. She doesn't keep track of her patterns either. She constantly works so we don't even get to try that often. Our situation is complicated and I'm not sure any traditional tests or methods are going to help or apply to us.