Does prior knowledge of maternal age affect judgment of operators measuring nuchal translucency?

To test the hypothesis that, in real life standard clinical practice, knowledge of maternal age (MA) by operators measuring nuchal translucency (NT) for screening of aneuploidy may influence their judgment, resulting in a tendency to over-measurement in older women.

We retrospectively analyzed the correlation between MA and NT MoMs in data from a group of operators from several clinical practices, with different levels of experience.

We assessed 66,918 measurements by 41 operators. There was no association between NT and MA in all the measurements analyzed together In 3 experienced operators (N > 1900), there was a significant association between the variables, although all were negative and its effect size was very small (0.004, 0.006 and 0.01). However one of the less experienced operators (N = 47) had a statistically significant (p = 0.0002) and strong (R2 = 0.2634) association. We tested the hypothesis that this bias could occur in less experienced operators but time/experience would correct it. We did the same analyses for each set of 50 tests, sorted by date, for each operator up to the 7th set. No significant progression was identified in association with increase in experience.

Our data does not support the hypothesis that operators might be biased towards over-measuring NT in older women.