The performance of an intermediate 16th-week ultrasound scan for the follow-up of euploid fetuses with increased nuchal translucency.

OBJECTIVE

The objective of the study is to assess the utility of an intermediate ultrasound scan at 16(+0) to 18(+6)  weeks of gestation in euploid fetuses with increased nuchal translucency ≥ 3.5 mm.

METHODS

Three hundred eighty-nine fetuses with nuchal translucency (NT) ≥ 3.5 mm were identified in two prenatal centers between January 2008 and December 2012. Pregnancy work-up included karyotyping, monthly detailed ultrasound scan starting with a 16th-week scan, a cardioechography, and a genetic counseling. Abnormal findings and pregnancy outcomes were analyzed retrospectively.

RESULTS

Of the 389 fetuses included, 52% had normal karyotype. Among euploid fetuses, 51 (30.7%) structural defects were identified overall. First-trimester scan was useful to identify 16 of the major defects (31.3%), and the 16th-week scan was useful to identify an additional 21 of them (41.2%), whereas the 22nd-week pregnancy scan discovered an additional 14 (27.4%). Structural defects discovered with the 16th-week scan were cardiac defects (n = 7), polymalformative syndromes (n = 3), left diaphragmatic hernias (n = 3), limbs abnormalities (n = 2), genitourinary (n = 2), microretrognathism (n = 2), hydrops (n = 1), and exomphalos (n = 1). If the intermediate scan was normal, the chances of a favorable outcome were as high as 85% and were close to 100% after 20 weeks, irrespective of initial NT.

CONCLUSION

The intermediate ultrasound was useful in fetuses with increased NT pregnancy work-up.