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Table 2 Estimates of mean, intracluster correlation coefficients (ICC), their respective 95% CI, design effect (Deff), and mean cluster size (n a ) for numeric maternal characteristics

From: Intracluster correlation coefficients for the Brazilian Multicenter Study on Preterm Birth (EMIP): methodological and practical implications

Variable Mean ICC 95% CI for ICC Deff na
Age (years) 26.1 0.018 0.004-0.033 5.3 265
Month stopped working 6.9 0.015 <0.001-0.032 2.6 99
Workload (hours daily) 8.0 0.040 0.007-0.072 6.9 98
Pre-pregnancy weight (Kg) 62.1 0.021 0.005-0.038 6.6 250
Height (m) 1.6 0.041 0.011-0.071 9.8 238
Final weight (Kg) 73.2 0.022 0.005-0.040 6.4 237
Weight gain in pregnancy (Kg) 10.9 0.012 0.001-0.023 4.5 229
Initial Body Mass Index (Kg/m2) 24.4 0.012 0.001-0.024 4.5 230
Final Body Mass Index (Kg/m2) 28.7 0.016 0.002-0.030 5.5 220
Number of pregnancies 2.4 0.006 <0.001-0.013 2.8 265
Number of vaginal deliveries 0.8 0.005 <0.001-0.011 2.5 265
Number of cesarean sections 0.3 0.014 0.002-0.025 4.7 265
Number of abortions 0.3 0.006 <0.001-0.013 2.3 265
Number of uterine curettage 0.2 0.008 <0.001-0.015 2.9 264