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Table 4 Estimates of prevalence (P), intracluster correlation coefficients (ICC), their respective 95% CI, design effect (Deff), and mean cluster size (n a ) for categorical variables of process during pregnancy

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

Variable P (%) ICC 95% CI for ICC Deff na
Healthcare facility used for prenatal care:     
   Primary health care unit 71.3 0.117 0.044-0.191 31.1 256
   Hospital 34.3 0.185 0.079-0.291 46.2 256
   Private clinic 9.3 0.051 0.015-0.086 15.9 256
   Other 0.3 0.005 <0.001-0.011 2.4 256
   Without prenatal care 3.2 0.003 <0.001-0.008 2.2 256
Prenatal care by physician 89.7 0.195 0.085-0.305 64.5 256
Start of prenatal care (1st trimester) 64.8 0.034 0.009-0.059 8.9 219
Number of prenatal care visits (≥6) 58.8 0.054 0.016-0.092 13.7 231
Ultrasound during prenatal care 98.4 0.001 <0.001-0.004 1.4 254
Physical effort 42.0 0.053 0.016-0.089 14.8 263
Depression 32.5 0.073 0.024-0.122 26.2 263
Anxiety 65.5 0.099 0.035-0.163 38.0 263
Smoking 13.5 0.020 0.004-0.036 7.7 265
Use of alcohol 15.9 0.031 0.008-0.054 10.2 263
Illicit drugs use (during or before) 4.9 0.015 0.002-0.027 5.8 265
Vaginal discharge treatment (self-reported) 36.6 0.010 0.001-0.020 4.1 264
Vulvovaginitis:      
   Bacterial vaginosis 12.9 0.039 0.008-0.069 11.1 160
   Candidiasis 13.5 0.061 0.016-0.106 11.2 160
   Trychomoniasis 1.4 0.011 <0.001-0.023 4.9 160
   Other vulvovaginitis 0.9 0.030 0.005-0.054 6.2 160
Vulvovaginitis treatment (registered) 24.1 0.073 0.020-0.126 15.1 164
Urinary infection treatment (self-reported) 36.3 0.018 0.004-0.032 6.7 261
Urinary infection (registered) 32.9 0.032 0.008-0.057 10.0 209
   Asymptomatic bacteriuria 15.7 0.084 0.027-0.140 23.2 184
   Cystitis 7.1 0.028 0.006-0.050 7.9 184
   Pyelonephritis 2.0 0.003 <0.001-0.008 2.0 184
Urinary treatment (registered) 2.1 0.075 0.023-0.126 18.2 184
Periodontal infection 17.0 0.036 0.010-0.063 14.5 262
Other infection 9.1 0.019 0.004-0.035 7.5 263
   Unknown fever 1.8 0.024 0.006-0.043 11.1 265
   Diarrhea fever 0.9 0.006 <0.001-0.012 3.2 265
   HIV - diagnosis in pregnancy 0.6 0.002 <0.001-0.006 2.1 265
   Pneumonia 0.5 <0.001 <0.001-0.003 1.2 265
   Tuberculosis <0.1 <0.001 <0.001-0.003 0.8 265
   Sinusitis/tonsillitis 3.4 0.015 0.003-0.028 6.7 265
   Hepatitis 0.2 0.007 <0.001-0.014 4.2 265
   Genital herpes <0.1 0.001 <0.001-0.004 1.4 265
   Toxoplasmosis 0.5 0.009 <0 001-0.018 3.4 265
Anemia 29.2 0.046 0.013-0.078 13.4 259
Iron replacement 84.9 0.037 0.001-0.063 12.1 264
Bleeding 23.9 0.012 0.001-0.022 4.6 264
   Bleeding in first trimester 12.2 0.006 <0.001-0.013 2.6 264
   Bleeding in second trimester 6.7 0.002 <0.001-0.006 1.6 264
   Bleeding in third trimester 6.3 0.013 0.002-0.024 6.1 264