Umbilical Cord Diameter at Early Second Trimester: Relation to Trisomy 21

To compare the umbilical cord diameter (UCD) at early second trimester (at 17–19 weeks of gestation) in trisomy 21 and normal fetuses and determined value of measuring UCD in screening trisomy 21.

This was a case–control study. The UCD was measured in 39 fetuses with trisomy 21 (documented by chorionic villus sampling or amniocentesis) and 39 fetuses in control group at 17–19 weeks of gestation. The control groups were low‑risk fetuses for aneuploidy in routine screening and were shown not to have aneuploidy after birth.

Mean of UCD in fetuses with trisomy 21 was lower than normal fetuses, but there were no significant differences between them (7.48 ± 0.99 mm vs. 7.66 ± 0.91 mm; P = 0.41). Mean of UCD had no significant difference between other maternal variable, for example, body mass index and obstetric history. Mean of UCD among mothers who had previous cesarean section was significantly lower than without it (7.21 ± 0.97 vs. 7.71 ± 0.97; P = 0.03).

At 17–19 weeks of gestation, the UCD of fetuses with trisomy 21 is thinner than normal, but the importance of this difference is too small for using this measurement in screening.