ABSTRACT
In the last two decades, considerable advances have been made in obstetric ultrasonography due to improved equipment and expertise. Routine ultrasonography is of value in determination of gestational age and placental localization, diagnosis of multiple pregnancies, and evaluation of fetal growth. The value of routine ultrasonography in screening for fetal malformations has been the subject of debate in recent years. It is imperative that such a screening in an unselected population of pregnant women should have high sensitivity and specificity and should have a high predictive value even when the prevalence of the conditions is low. Despite their low prevalence (ranging from 2% to 4%) fetal structural malformations are responsible for approximately 20% to 30% of perinatal mortality in developed countries (1-3). The vast majority of these malformations occur in low-risk pregnancies (4). The ideal timing for screening in a low-risk population seems to be a compromise between obtaining adequate images for diagnosis in the majority of routine patients, scanning sufficiently late not to miss late-developing lesions, and yet offering diagnosis as early as possible for parents to consider their options.
