Is there any advantage of doing an earlier screening scan in pregnancy (12 weeks) to detect anomalies, or is it preferable to wait for the regular scan at 18-20 week.?
It is noe becoming almost routine to perform a scan at around 11-14 weeks, mainly to look for an increased nuchal translucency and absent fetal nasal bone for the detection of chromosomal anomalies. With the documentation of an absent nasal bone and a thickened nuchal translucency in the fetus the chance of Trisomy 21 is much increased. More recently the presence of triscuspid regurgitation are also looked at to increase the detection rate. The screening is usually performed with the abdominal rather than the vaginal scan. A repeat scan at about 18 to 20 weeks will still be necessary for such anomalies as cardiac, spinal, intracranial and facial abnormalities.
