Screening ultrasonography in pregnancy

ABSTRACT

Ultrasonography in obstetrics is increasingly used for the screening of chromosomal abnormalities as well as for prenatal diagnosis of congenital abnormalities with safety and technological advancements. In the first trimester, it is important to confirm normal intrauterine pregnancy with viability, detect the abnormalities of uterus and adnexa, determine the number of fetuses and assess chorionicity and amnionicity in case of multiple pregnancy. After establishment of gestational age accurately by crown-rump length, thickened fetal nuchal translucency, absence of nasal bone, tricuspid regurgitation, reverse a wave of ductus venosus and cystic hygroma can be markers for screening of chromosomal abnormalities. In addition, the scan also offers an opportunity to detect gross structural abnormalities, which could help improve the prognosis by early prenatal intervention. In the second trimester, aneuploidy (trisomy 21, 18, 13, Turner syndrome) and genetic syndromes could be detected by major structural defects and soft markers. It is important to consider that many malformations may not be detected prenatally even by qualified practitioners and appropriate equipment, and to counsel patients about the potential for false-positive or false-negative results.