Disorders

Disorders such as neural tube defects, severe skeletal
dysplasias, abdominal wall defects and renal abnormalities may
all be detected by ultrasonography between 17 and 20 weeks’
gestation. Centres specialising in high resolution
ultrasonography can detect an increasing number of other
abnormalities, such as structural abnormalities of the brain,
various types of congenital heart disease, clefts of the lip and
palate and microphthalmia. For some fetal malformations the
improved resolution of high frequency ultrasound transducers
has even enabled detection during the first trimester by
transvaginal sonography. Other malformations, such as
hydrocephalus, microcephaly and duodenal atresia may not
manifest until the third trimester.