Umbilical cord index in fetuses with and without aneuploidy

Backgroud: Sonographic abnormalities of the umbilical cord (UC) such as single umbilical artery, thick cord, short cord and disorders of the coiling pattern have been linked to aneuploidy. Particularly uncoiled UC's below 20 weeks of gestation have recently been associated with Down Syndrome. The present study was planned to explore the association between the UC coiling index (UCI) of normal fetuses compared to UC from fetuses with aneuploidy in the second half of gestation.

Materials and Methods: A case control study was designed. Fetuses with confirmed aneuploidy during prenatal diagnosis above 20 weeks of gestation were matched one-to-two with normal controls of similar gestational age. Color flow mapping was used to enhance the definition of the UC and its vascular coils. The length of one complete coil (two arteries and one vein) was measured and the UCI was defined as the reciprocal value of that measurement. Nonparametric tests were used for statistical analysis.

Results: During the study period 11 fetuses with aneuploidy (trisomy 21 n=3; trisomy 13 n=1; turner syndrome and mosaicism n=2); Di George syndrome n=2; Cri-du-chat syndrome n=3) and 22 normal fetuses were included into the study. No difference in the median (range) gestational age at study inclusion between groups was found (cases: 33.1 (23–37.3) vs. controls: 33.1 (23–37.4) weeks; p=ns). The median (range) difference in gestational age was 1 (0–3) days. No difference was found comparing the UCI (cases: 0.41±0.18 vs. controls: 0.43±0.27; p=0.90). Moreover the prevalence of uncoiled UC's was statiscally not different, which was 9.1% in both groups.

Conclusions: Although abnormal sonographic umbilical cord coiling patterns are a marker of genetic fetal abnormalities in early pregnancy, this observation seems not to be valid for late pregnancy.

aneuploidy - early pregnancy - umbilical cord coiling index