Enlarged heart? 20 week scan

I recently was told by my midwife that my baby’s heart was measuring slightly larger than normal in the 20 week scan. Everything else looked normal & healthy. I’ve been referred to a specialist to have another scan. She was quite confused and said she hadn’t really seen this before so wasn’t sure what it could be and the radiologist’s wouldn’t tell her anything. She said it could have just been a wrong measurement or something but we just have to check. Has anyone else gone through something like this? I’m so confused, worries & don’t know what to think, I’ve tried to look online but can’t find any info. Thanks x