Intracranial translucency at 11–13 weeks of gestation: prospective evaluation and reproducibility of measurements

ABSTRACT Objective This paper aimed to determine the feasibility of identification and measurement reproducibility of intracranial translucency (IT) in our population. Methods This is a prospective study in which five accredited operators attempted to identify and measure the IT during first‐trimester sonographic screening for aneuploidy in 990 fetuses. The presence or absence of spina bifida was determined at the time of the second‐trimester scan or after birth. Measurement reproducibility was assessed through intraclass correlation coefficient (ICC) on a subgroup of 150 fetuses. Results Identification and measurement of the IT were possible in 961 (97%) cases. The mean IT anteroposterior diameter was 1.8 mm (SD ± 0.37; range 0.8–3.1), and the size increased linearly with advancing gestation (IT = 0.74 + 0.02 × crown–rump length; r 2 = 0.15, p < 0.0001). The only fetus with spina bifida in this series presented with absent IT. Intra‐observer and inter‐observer ICCs were 0.79 and 0.75, respectively (95% confidence intervals 0.72–0.84 and 0.67–0.81, respectively; both p < 0.001). Conclusions The IT increases linearly with increasing crown–rump length and seems to be of value in the first‐trimester detection of spina bifida. It is easy to identify and measure and shows excellent intra‐observer and inter‐observer reproducibility measurements. © 2012 John Wiley & Sons, Ltd.