Comparison of pregnancy outcome of euploid fetuses with increased nuchal translucency (NT) expressed in NT MoM or delta-NT

Objective To evaluate the outcome of euploid fetuses with increased nuchal translucency thickness (NT) expressed in multiples of the median (MoM) or delta-NT. Methods Included in the study were euploid fetuses with increased NT greater than or equal to 95(th) centile, for which information about pregnancy outcome was available. The following parameters were defined as an adverse outcome: miscarriage, structural anomalies justifying termination of pregnancy, and structural anomalies, genetic syndromes and neurodevelopmental problems diagnosed postnatally. Fetal outcome according to NT MoM and delta-NT was calculated using different cut-off values. Calculations of the odds ratio for adverse outcome were performed using either NT MoM or delta-NT as a predictor in logistic regression models. Results The study comprised 168 euploid fetuses. Of these, 38 (23%) bad an adverse outcome: 11 (6%) had miscarriages, 14 (8%) were terminated because of fetal abnormalities detected on the prenatal scan and 13 (7%) were found postnatally to have abnormalities. The incidence of cases exhibiting an adverse outcome was 5.3%, 19.2% and 58.5% for NT values of 1.6-1.9, 2.0-3.0 and > 3.0 MoM, respectively (P < 0.0001, chi(2) test), and 3.9%, 16.7% and 62.8% for delta-NT values of 1.0-1.4, 1.5-2.5 and > 2.5 mm, respectively (P < 0.0001, chi(2) test). Using cut-offs of 2.0 MoM and delta-NT of 1.5 mm, the odds ratios for adverse outcome were 10.2 (95% CI, 3.4-30.4) and 15.4 (95% CI, 4.2-43.6), respectively. Conclusion Both the NT MoM and delta-NT approaches may be used to determine cases which require additional antenatal investigation as well as fetal karyotyping. For this purpose we suggest using a cut-off of either 2.0 MoM or a delta-NT of 1.5 mm. Copyright (C) 2004 ISUOG. Published by John Wiley & Sons, Ltd.