Obstetric ultrasonography is the use of medical ultrasonography in pregnancy, in which sound waves are used to create visual images of the developing embryo or fetus in the uterus. The procedure is a standard part of prenatal care in many countries, as it can provide a variety of information about the health of the mother, the timing and progress of the pregnancy, and the health and development of the embryo or fetus. The International Society of Ultrasound in Obstetrics and Gynecology recommends that pregnant women have routine obstetric ultrasounds between 18 weeks' and 22 weeks' gestational age in order to confirm pregnancy dating, to measure the fetus so that growth abnormalities can be recognized quickly later in pregnancy, and to assess for congenital malformations and multiple pregnancies. Empty your bladder 90 minutes before exam time, then consume one 8-ounce glasses of fluid about an hour before exam time. We recommend a two-piece outfit so we can access your abdomen without you removing your clothing.