Obstetric ultrasonography, or prenatal ultrasound, is the use of medical ultrasonography in pregnancy, in which sound waves are used to create real-time visual images of the developing embryo or fetus in the uterus (womb). 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. This book consists of 4 chapters including: Chapter I (Introduction),Chapter II (Ultrasound in the Second Trimester),Chapter III (Ultrasound in Twin Pregnancy),Chapter IV (Abnormalities of the Placenta in Ultrasound),Chapter V (Ultrasound assessment of amniotic fluid),Chapter VI (Ultrasound in the Third Trimester). It is hoped that this book will help students and interested people as an important and scientific resource.