Ultrasound screening for anencephaly at 10-14 weeks of gestation.

In an ongoing study involving seven hospitals in London and surrounding areas, 55,237 fetuses were examined by ultrasound at 10-14 weeks of gestation. There were 47 fetuses (1 in 1175) with anencephaly which presented with acrania with varying degrees of cerebral degeneration. The first audit of results was performed in April 1995. During the first phase of the study 34,830 fetuses were examined and in eight of the 31 with anencephaly the diagnosis was not made at the 10-14-week scan. Following the audit, 20,407 fetuses were examined and in all 16 with anencephaly the diagnosis was made at the 10-14-week scan (p = 0.03). These findings demonstrate that anencephaly can be reliably diagnosed at the routine 10-14-week ultrasound scan, provided a specific search is made for the sonographic features for this condition.