Measurement of the fetal umbilical cord insertion-to-genital tubercle length in early gestation: in utero sonographic study.

Objectives: The purpose of this study was to establish in utero reference ranges for the fetal umbilical cord insertion-to-genital tubercle length in early gestation.

Methods: A prospective cross-sectional study was performed on 140 normal low-risk singleton pregnancies between 12 and 18 weeks' gestation. The umbilical cord insertion-to-genital tubercle length was measured in a midsagittal section with high-resolution transvaginal or transabdominal sonography. The mean and 95% prediction limits were defined for each gestational week and analyzed by regression equations and correlation coefficients.

Results: Adequate measurements were obtained in 134 patients. The umbilical cord insertion-to-genital tubercle length as a function of gestational age was expressed by the following regression equation: umbilical cord insertion-to-genital tubercle length = -3.079452 + 1.09 × week (R(2) = 0.7117). The correlation R(2) = 0.7117 was found to be highly statistically significant (P < .001). The normal mean and 95% prediction limits were defined for each gestational week. During the study period, 2 cases were referred to our unit because of nonvisualization of the urinary bladder. The umbilical cord insertion-to-genital tubercle lengths in these cases were below the 95th percentile, confirming the diagnosis of bladder exstrophy.

Conclusions: The normative data established in this study may be helpful for early pre-natal diagnosis congenital bladder exstrophy.