My girlfriend is about 9 weeks pregnant. She went to the doctor and they did the ultrasound and told her that the heartbeat sounded healthy and she seemed healthy, but that she had a really thick lining. They seemed to think it was too thick for the stage she is in. She has a history of endometriosis in her family and I am wondering if it has something to do with that. Do women often miscarry due to a lining that is too thick? I also heard it could be due to the chance of having twins, but she has no history of having twins in her family. Any help would be appreciated. Thanks.