Umbilical cord diameter at 11-14 weeks of gestation: relationship to nuchal translucency, ductus venous blood flow and chromosomal defects.

OBJECTIVE: To compare the umbilical cord diameter (UCD) in euploid and aneuploid fetuses at 11-14 weeks of gestation.

METHODS: In 299 fetuses at 11-14 weeks of gestation the UCD, the nuchal translucency and the a-wave of the ductus venosus were measured. Reference ranges for the UCD according to the gestational age and to the crown-rump-length (CRL) were obtained by measuring the UCD by outer-to-outer border of 244 singleton pregnancies with normal karyotype. The fetal karyotype was established by chorionic villus sampling, amniocentesis or in case of suspected chromosomal abnormalities in the newborn. Linear regression was used to determine the significance of the association between the UCD and CRL or gestational age.

RESULTS: Two hundred and ninety-nine fetuses were examined. The median fetal CRL was 64.5 mm (range 45-84) and the median gestational age was 13 (range 11-14) weeks. In the chromosomally normal group the UCD significantly increased with the CRL (r=0.620; p<0.001) and the gestational age (r=0.555; p<0.001). The regression equation for the mean UCD (y) according to the gestational days (x) was: y=-0.604+0.051*x. The regression equation for the mean UCD (y) according to the CRL (x) was: y=1.962+0.029*x. There were no significant differences in the mean UCD in fetuses without and with chromosomal abnormalities. The proportion of fetuses with an UCD above the 95th centile for CRL was higher in aneuploid compared to euploid fetuses (5/14 vs. 13/285, p<0.005). In 5/14 (35.7%) fetuses with chromosomal defects the NT and the UCD were above the 95th centile, whereas none of the fetuses with normal karyotype showed this combination. The proportion of fetuses with increased UCD and abnormal DV blood flow was increased in the cases with chromosomal abnormalities (33.3 vs. 1.8%, p<0.005).

CONCLUSION: Umbilical cord diameter at 11-14 weeks increases with fetal CRL. Fetuses with chromosomal abnormalities are more likely to have an UCD above the 95th centile. Therefore, sonographic evaluation of the umbilical cord during first trimester ultrasound might be of additional value in the assessment of fetuses at risk for aneuploidies.