Some anomalies could have been detected in
11-14 weeks scan but the ultrasound scan in the present
study missed. Items such as the skeletal dysplasia,
tibial aplasia and some aneuploidies were missed.
Signs of trisomy 21 might be seen in the first trimester
such as the fetal nasal bone but were missed. Sonomarkers
of trisomy18 or 13 might also be already
visible in the first trimester such as the megacystis,
omphalocele, polydactyly and holoprosencephaly(15),
but these sonographic signs were missed as well.
Although the majority of the fetal anomalies were
diagnosed in early pregnancy, a single scan in early
pregnancy will not detect all fetal abnormalities, as
described above. The detection rate is increased significantly
by adding a mid-second-trimester scan to the
early pregnancy scan. Therefore, the 18-20-week followup
examination by conventional second-trimester
transabdominal scan should always be performed(16).