Ultrasound in Pregnancy – From Ultrasound Physics to Morphological and Functional Measurements of the Fetus

Ultrasound is the leading technology to monitor the progress of pregnancy and the fetal condition. This chapter presents the basic principles of ultrasound, including the generation of ultrasound pressure waves through electromechanical conversion, their propagation through lossless and lossy media, and the formation of ultrasound images using array transducers. Special attention is dedicated to the resolution of the imaging system, which affects the accuracy of the morphological measurements performed during pregnancy. Besides imaging, ultrasound Doppler principles have provided important solutions for the estimation of blood velocity. The available solutions, ranging from continuous- to pulsed-wave Doppler, up to more advanced color and power Doppler, are presented and critically discussed for their advantages and limitations in pregnancy. The last part of the chapter is dedicated to the clinical use of ultrasound in pregnancy. The main ultrasound tests are presented in chronological order from the first to the third trimester of gestation, monitoring pregnancy progression from embryo development all the way to labor and delivery. Latest developments, such as dynamic 3D and ultrafast imaging, are also briefly presented, along with their expected impact on pregnancy monitoring.