Anyone experience this with their twins? A 15% size difference was confirmed at my ultrasound today. I'm currently 23 weeks. Doc said if it gets to 20% we have a problem, but right now we just need to keep an eye on it. One twin is the 74th percentile and the other in 30th. Both are normal, we just don't want to see this size difference increase. They will do another growth scan in 4 weeks.