highly significantP < 0.0001
After stratification by plurality of birth, somewhat weaker but still highly significant associations of ART with ARM were seen among both singletons (OR, 7.7; 95% CI, 4.6–12.7; P < 0.0001) and multiple births (OR, 4.9; 95% CI, 2.4–10.1; P < 0.0001) (Table 5 ).