Fetal Nuchal Translucency Measurements: Performance of Midwives and Doctors Compared

Abstract

Objective: To compare (a) the performances in fetal nuchal translucency for multiple of median, and false-positive Down syndrome detection rates in doctors and midwives, and (b) the same parameters as obtained using the two models of ultrasound machines.
Methods: We conducted a retrospective review of all pregnancies with fetal nuchal translucency measurements in a public hospital in Hong Kong from July 2010 to December 2011. We compared demographic factors, fetal nuchal translucency multiple of median values, and false-positive Down syndrome detection rates by doctors and midwives. We also compared the same parameters obtained by the two models of ultrasound machines (Philips IU22 [US] and Medison V20 [Korea]) that were used. Both the doctors and midwives responsible for fetal nuchal translucency measurements were certified Hospital Authority sonographers who had completed the Fetal Medicine Foundation training, and were supervised until deemed fit for independent scanning, and their performance was monitored. A standardised protocol for fetal nuchal translucency measurements was adopted from Fetal Medicine Foundation. Both models of the ultrasound machines were equipped with high-resolution ultrasound probes. A pre-set protocol for measuring nuchal translucency was available in both machines. Independent paired t tests and Chi-square tests were used to analyse the parametric and non-parametric data, respectively.
Results: A total of 5983 first-trimester screens for Down syndrome were performed from July 2010 to December 2011. Among these, 1262 (21.1%) and 4721 (78.9%) screenings were performed by doctors and midwives, respectively. In all, 5746 (96.0%), 217 (3.6%), and 9 (0.2%) of the fetal nuchal translucency measurements were performed using the Philips IU22, Medison V20, and another ultrasound machine, respectively. Between doctors and midwives, there were no differences in the mean fetal nuchal translucency multiple of median values (0.97 vs. 0.98; p=0.081), the false-positive rates (7.1% vs. 5.8%; p=0.15), and the Down syndrome detection rates (100% vs. 94.1%; p=0.742). There was also no difference in the mean nuchal translucency multiple of median values obtained by the two models of ultrasound machines (Philips IU22 and Medison V20) being compared, respective values being 0.98 vs. 1.01 (p=0.152).
Conclusion: It seems that the performance of trained midwives in measuring fetal nuchal translucency is comparable to that of trained doctors. Our preliminary results did not show a significant difference in fetal nuchal translucency multiple of median values obtained by the two ultrasound machines when using standardised settings.