Umbilical cord stricture is not a genetic anomaly: a study in twins

Two recent reports on recurrent cases of umbilical cord stricture (UCS) have opened the debate on the possibility of a genetic basis for this anomaly, traditionally considered to be sporadic. We present a series of 130 cases of UCS located at the fetal insertion, diagnosed among 2067 fetal and infantile autopsies performed during the last 10 years. All cases were macerated stillborn fetuses, and 54.6% were < or =20 weeks of gestational age. Our study is focused on 2 recurrent episodes and 16 cases occurring in multiple pregnancies. Among twins, males were affected more than females (2.2:1), although no statistical significance was found. Associated umbilical cord anomalies were present in 8 of 16 cases, consisting of hypocoiling (3 cases), hypercoiling (2 cases), excessive length (1 case), vascular tortuosity (1 case), and single umbilical artery (1 case). The most frequent placental finding was obliterative endovasculopathy (6 cases), probably indicating a causal relationship with UCS. Zygosity was analyzed by placental histology and/or a panel of 12 microsatellite markers to classify twins as monozygotic (8 cases) or dizygotic (8 cases). Our data prove that UCS is not a genetic condition because all 8 genetically identical twins were discordant for the anomaly and 2 dizygotic twins with UCS had co-twins also affected. Genetic factors are not implicated in UCS pathophysiology, and parents with a fetal demise due to UCS should be counseled as having a low-recurrence risk for subsequent pregnancies. Because there is not a higher incidence of UCS in multiple gestations, twinning should not be considered a risk factor for UCS.