Genetic Influence on Dystocia

Abstract

ABSTRACT

Dystocia, a prolonged and difficult labor, complicates from 3% to 8% of all deliveries worldwide. There is evidence of familial aggregation of the disorder, prompting this population-based retrospective study using registry information on dystocia in sisters and mothers. The goal was to detect any genetic influences on susceptibility to dystocia. The study group included 2,539,534 births taking place in Sweden from 1973 through 1997. Relationships between sibling and mother–daughter pairs were examined, and model fitting served to estimate the relative contributions of genetic and environmental factors to dystocia.

The incidence of dystocia, identified in 190,747 births, was 8%. Compared with a monozygotic twin whose cotwin did not have dystocia, 1 whose cotwin did have dystocia exhibited a nearly 4-fold increase in the risk of dystocia. Considering all diagnoses of dystocia, the odds ratio was highest for monozygotic twins at 3.82. For dizygotic twins (biologically full-sisters), half-sisters with the same mother, and mother–daughter pairs, the respective odds ratio values were 1.66, 1.85, and 1.60. Half-sisters sharing the same father had a lower risk of dystocia. Model fitting suggested that genetic effects accounted for 28% of susceptibility to dystocia (95% confidence interval, 21–32%). Nonshared environmental factors accounted for 67% of susceptibility. The same patterns were found for primary and secondary dystocia. When analyzing women with primary dystocia who had cesarean section, the risk of dystocia was significantly elevated only in monozygotic twins and mother–daughter pairs.

These findings suggest that detecting genes related to dystocia might clarify the pathophysiological of this disorder, and might make it possible to detect, before parturition, an increased risk of dystocia.