The embryology and pathophysiology of nuchal translucency (NT) are still not entirely known. Current guidelines recommend measuring NT in fetuses with a Crown–rump length (CRL) of 45-84 mm. The aim of this study was to assess the significance and the evolution of enlarged NT if detected before the CRL of 45 mm. Retrospective observational study. Information about NT measurements performed at our centre in 2005-2016 was retrieved from the database. We searched for cases of singleton pregnancies with viable fetuses and with NT above the 95th centile observed before the CRL of 45 mm, and for which a second NT measurement was performed in the recommended CRL of 45-84 mm. The information about a fetal karyotype, a result of first-trimester combined test, ultrasound scan at 20 weeks and pregnancy outcome was recorded. In total, 44067 women had the NT scans during the period. Of these, 17 cases with paired measurements were eligible for the analysis. The average CRL of the first NT measurement was 38 mm (range 31-44 mm), the average of the second measurement was 57 mm (range 45-73 mm). In 8 (47%) fetuses the NT measurement was found to be below the 95th centile at the second measurement. The risks from combined test were low (range 1/440-1/25000), CVS was performed in one case with normal karyotype and in all these cases ultrasound scans at 20 weeks were normal and healthy neonate were born. However, NT remained enlarged at the second measurement in 9 (53%) cases. Of these, an abnormal karyotype was found in 4 (44%) cases, one (12%) fetus had a complex cardiac anomaly, and in 4 (44%) cases the karyotype was normal and a healthy neonate was born. The results of our study suggest that the significance of enlarged NT detected before the CRL of 45 mm is questionable. The second evaluation with the recommended CRL of 45-84 mm is warranted and the NT thickness falls below the 95th centile in 47% of cases. If the enlargement disappears and the risk from combined test is low, the pregnancy outcome is excellent.