Ultrasound Surveillance of Twin Pregnancy: I. Conception to the Mid-trimester

Abstract

The phenomenon of twinning is a unique, biological experiment shrouded in social and scientific curiosity. More commonplace in animals than in humans, it is a fascinating example of survival of the fittest. Co-habitation of two or more fetuses within a common uterus markedly heightens the risk of disease and death for these multiples throughout their entire life cycle, but health and survival are undoubtedly influenced most by events in the perinatal period. Ultrasonography has enabled us to be conscientious observers of this experiment, has allowed us to chronicle developmental milestones in multiple pregnancy, and has guided therapeutic interventions in the management of these challenging cases. Modem high resolution imaging technology has delivered additional information regarding the epidemiology of plural pregnancies and has given us an appreciation of some of the complex, pathophysiological mechanisms which result in poorer obstetrical outcomes.Part I of this two-part series reviews applications of antenatal ultrasound in the diagnosis of twin pregnancy, assessment of chorionicity/amnionicity, detection of anomalies and identification of pathological twin states. Part II of the series will address the differing roles of sonography in mid to late gestation: prediction of preterm labour, assessment of fetal growth and well-being, guiding invasive techniques and intrapartum applications. Ultrasonography is an integral part of contemporary management of multiple pregnancies from conception through confinement.