Sonographic markers for early diagnosis of fetal malformations

Abstract

Fetal malformations are very frequent in industrialized countries. Although advanced maternal age may affect pregnancy outcome adversely, 80%-90% of fetal malformations occur in the absence of a specific risk factor for parents. The only effective approach for prenatal screening is currently represented by an ultrasound scan. However, ultrasound methods present two important limitations: the substantial absence of quantitative parameters and the dependence on the sonographer experience. In recent years, together with the improvement in transducer technology, quantitative and objective sonographic markers highly predictive of fetal malformations have been developed. These markers can be detected at early gestation (11-14 wk) and generally are not pathological in themselves but have an increased incidence in abnormal fetuses. Thus, prenatal ultrasonography during the second trimester of gestation provides a “genetic sonogram”, including, for instance, nuchal translucency, short humeral length, echogenic bowel, echogenic intracardiac focus and choroid plexus cyst, that is used to identify morphological features of fetal Down’s syndrome with a potential sensitivity of more than 90%. Other specific and sensitive markers can be seen in the case of cardiac defects and skeletal anomalies. In the future, sonographic markers could limit even more the use of invasive and dangerous techniques of prenatal diagnosis (amniocentesis, etc.).

Keywords: Prenatal diagnosis; Prenatal sonography; Chromosome abnormalities; Nuchal translucency; Fetal echocardiography; Skeletal dysplasia

Core tip: The aim of this paper is to review sonographic markers associated with the most frequent fetal abnormalities (chromosomal anomalies, cardiac defects, skeletal dysplasia) and their sensitivity in prenatal diagnosis. Fetal malformations are very frequent in industrialized countries and the only effective approach for prenatal screening is currently represented by an ultrasound scan. Early detection of abnormalities can optimize pregnancy management and childbirth timing, give the possibility of performing simpler procedures for termination of pregnancy in those patients in whom findings are abnormal, and plan therapeutic treatment of objectively selected diseased fetuses.