My wife is 22 weeks along with fraternal twins through IVF. We have been seeing the prenatalist for high level ultrasound. Everything came out fine so far, and the babies are 1.5 pounds each. Her gynecologist was very comfortable with the overall findings up till now. After examining the physical, her prenatalist advised that her belly size is too big and her uterus is about the full-term already and recommended to get her cervix sized measured by her gynecologist on our next scheduled visit and indicated that pregnancy can be due preterm any time. On the other hand my wife has no indications/signs (contractions etc.) of going into preterm labor. Her gynecologist recommended my wife go on complete bed rest. Since then we are so much worried about our twins. Please advise if it is possible to tell if the pregnancy will be preterm by measuring the belly size and water bag being big by ultrasound finding. Also if this is OK, then what kind of precautions should we take and what are the chances for survival?