Routine ultrasound examination is defined as a screening procedure per
formed on the total obstetric population usually at 18-20 weeks of ges
tation as opposed to the selective use of ultrasound that might provid
e more information for a problem that is suspected on clinical grounds
. Standard ultrasound examination includes a comprehensive examination
of fetal anatomy as part of routine ultrasound. It is important for t
he clinician to realise that the comprehensive examination of fetal an
atomy is an essential, not optional, part of the routine examination.
Screening may lead to unnecessary anxiety if there is a false-positive
result, or to a false sense of security if there is a false-negative
result. The routine offering of obstetric ultrasound screening is the
central issue in the general question of whether every woman should re
ceive an obstetric ultrasound examination. The majority of countries h
ave adopted the following diagnostic strategy. All pregnancies must be
ultrasonographically tested in accordance with the protocols commonly
recommended. The ultrasonography done at 18-20 weeks, which is known
to be fundamental for diagnosing prenatal malformations, must always b
e performed at level II. Highrisk pregnancies of malformations are to
be selected in the first level of screening and referred to level II f
or further study. There is extensive literature neither supporting an
improvement in perinatal morbidity or mortality nor an overall :reduct
ion in unnecessary intervention with routine ultrasound. The role of r
outine ultrasonography and its validity as a screening test for fetal
malformation in a low-risk population is still the object of debate.