The use of first trimester ultrasound in routine practice.

Since the introduction of ultrasound scanning in early pregnancy, transabdominal or transvaginal ultrasonography has taken on an important role in routine clinical practice in terms of the care of the fetus and the mother. The use of ultrasound in very early pregnancy makes it possible to confirm the intrauterine living embryo or diagnose the extrauterine pregnancy in which medical treatment with low morbidity is feasible with early detection. Early scanning can provide exact dating with acceptable error, which is one of problems encountered in clinical practice. Chorionicity can be correctly established by early scanning (before 14 weeks of gestation) to manage multiple pregnancies properly. The nuchal translucency, which is a transitory abnormality, can be measured for the early screening of Down's syndrome, trisomy-18, trisomy-13, Turner's and some other aneuploidy at the 11-14 weeks gestation with approximately 80% detection rate. Early diagnosis of some major abnormalities such as anencephaly, megacystis, polycystic kidney, omphalocele is also possible by early scanning. This provides great advantages as the clinical management will be quite different for a case of omphalocele or megacystis. Therefore the early ultrasound scanning has become a routine standard method in the care of the pregnant woman.