Ultrasonography inObstetrics and GynecologyDepartment of Obstetrics andGynecology,Tongji HospitalXu Xiaoyan2014.10 Ultrasound in Obstetrics pregnancypregnancy is the maternalcondition of having adeveloping fetus in thebody.1.Start：fertilization.Estimated age of the fetus calculated from the firstday of the last menstrual period (LMP)2.Termination：delivery.Assuming a 28-day cycle, 280 days, 40 weeks3.There are about 266 days during pregnancy.？-14fertilizationD- -266D Ovulation-Delivery