Relationship between first trimester visualization of the intracranial translucency and spina bifida

To establish a reference range for the intracranial translucency (IT).

In this prospective study, we examined 596 singleton fetuses at 11-14 weeks of gestation using transabdominal ultrasonography. The distribution curves of the anterior-posterior diameter of the IT were established according to the gestational weeks, and the percentiles for 11-14 weeks of gestation were calculated. Regression analysis was performed to estimate the relationship between the anterior-posterior diameter of the IT and other fetal biometric parameters.

The mean anterior-posterior diameter of the IT was 1.8 ± 0.4 mm. From 11 to 14 weeks of gestation, the IT diameter increased linearly with advancing gestation. The linear regression equation for the IT × crown-rump length (CRL) was IT = CRL × 0.0184 + 0.575 (R = 0.385, p < 0.001). The linear regression equation for the IT × biparietal diameter (BPD) was IT = BPD × 0.0532 + 0.632 (R = 0.346, p < 0.001). The linear regression equation for IT × gestational age (days) (GA) was ICT = GA × 0.024 - 0.339 (R = 0.25, p < 0.001). The linear regression analysis revealed significant correlations of the IT with CRL, BPD, and GA.

The IT increases linearly with increasing CRL, BPD, gestational age in weeks, and gestational age in days.