The relationship between umbilical cord length and chronic rheumatic heart disease: a prospective cohort study

BACKGROUND: One previous, preliminary study reported that the length of the umbilical cord at birth is related to the risk of developing chronic rheumatic heart disease in later life. We sought to replicate this finding. DESIGN: Prospective, population-based birth cohort. METHODS: We traced 11,580 individuals born between 1915 and 1929 in Uppsala, Sweden. We identified cases with a main or secondary diagnosis of chronic rheumatic heart disease in the Swedish national inpatient, outpatient or death registers. Archived obstetric records provided data on umbilical cord length, gestational age, birthweight and placental weight. RESULTS: There were 136 patients with chronic rheumatic heart disease (72 men and 64 women) with a mean age at first hospital admission of 68 years (range 36-92). There was evidence of a positive association between umbilical cord length and risk of subsequent chronic rheumatic heart disease. The overall hazard ratio in the Swedish study (1.13, 95% confidence interval 1.01 to 1.27) was similar to that of the previous study, with some suggestion of larger effect in men than in women. No other birth characteristics were predictive except for weak evidence of a protective effect of higher birthweight in men. CONCLUSIONS: People with longer umbilical cords at birth are more likely to develop chronic rheumatic heart disease in later life. As longer umbilical cords have more spiral arteries and a higher vascular resistance, we hypothesize that the increased pressure load on the heart leads to changes in endothelial biology and increased vulnerability to the autoimmune process initiated by infection with β-haemolytic streptococci.