Approximately 6 percent of infants are delivered with a short umbilical cord. This condition has been associated with several abnormalities during pregnancy and complications of labor and delivery, but little is known about the etiology of short cord or its associated complications. Krakowiak and colleagues used a population-based, case-control study in one state of more than 17,000 singleton live births over 11 years to identify risk factors and adverse outcomes associated with a short umbilical cord.
They used a statewide database that linked information from birth certificates, hospital maternal and infant records, and infant deaths. The 3,565 infants diagnosed with short cords by any record of an appropriate International Classification of Diseases, 9th rev. (ICD-9) code were compared with 14,260 randomly selected control infants born in the same year. The variables of interest were possible causes or consequences of a short cord identified by previous studies. The latter included maternal body mass index (BMI), smoking, alcohol use, parity, previous poor outcomes of pregnancy, and several fetal characteristics.
During the study, more than 900,000 live singleton births were recorded, giving an incidence of four per 1,000 live infants born with a short umbilical cord. The mothers of the short-cord infants were likely to have more formal education and less likely to use Medicaid insurance than the control group, but these and other differences between the two groups were not statistically significant. The greatest differences between the study and control groups as assessed by the odds ratios (ORs) were in an excess of fetal malformation (OR, 1.6), oligohydramnios or polyhydramnios (1.4), first pregnancy (1.4), and female infant (1.3); and a relatively lower incidence of high BMI (0.7), hypertension (0.7), parity three or more (0.7), early amniocentesis (0.7), gestational diabetes (0.7), and eclampsia (0.3). Within the congenital malformations classification, infants with short cords had double the risk of chromosomal, gastrointestinal, and circulatory or respiratory malformations. Mothers of infants with short cords had increased risk of retained placenta, operative vaginal delivery, prolonged labor, and other complications of delivery. The short-cord infants had increased risk of being small for gestational age and having fetal distress. Overall, the relative risk of death within one year in infants born with a short umbilical cord was 2.4.
The authors conclude that the incidence of short cord was stable at about four per 1,000 live births each year. No modifiable risk factors for the condition were identified, but it was associated with certain congenital abnormalities. They recommend that infants born with short cords be monitored closely because of the observed high mortality during the first year of life.