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Table 5 Risk ratios and 95% confidence intervals for associations between average monthly PCE exposure (g) during the LMP year (percentiles) and individual ischemic placental diseases

From: Prenatal drinking-water exposure to tetrachloroethylene and ischemic placental disease: a retrospective cohort study

     Model 1: Unadjusted GEE     Model 2: Multivariable GEEa  
  Events/N RR 95% CI RR 95% CI
Placental abruptionb      
  Any 18/1,698 1.13 0.63, 2.04 1.19 0.65, 2.15
  ≥50th (5.7 × 10-1 g – 132 g) 11/846 1.36 0.69, 2.70 1.35 0.68, 2.67
  >0- < 50th (9.6 × 10-5 g – 5.7 × 10-1 g) 7/852 0.90 0.41, 1.97 0.90 0.41, 1.97
  0 28/3,062 1.00 Referent 1.00 Referent
Preeclampsiab      
  Any 8/1,721 0.35 0.16, 0.76 0.37 0.17, 0.83
  ≥50th (5.7 × 10-1 g – 132 g) 4/859 0.34 0.12, 0.97 0.36 0.12, 1.07
  >0- < 50th (9.6 × 10-5 g – 5.7 × 10-1 g) 4/862 0.37 0.14, 0.99 0.39 0.14, 1.10
  0 41/3,115 1.00 Referent 1.00 Referent
SGAc      
  Any 68/1,034 0.97 0.69, 1.35 1.04 0.75, 1.46
  ≥50th (5.7 × 10-1 g – 89.2 g) 38/600 0.91 0.61, 1.36 0.98 0.66, 1.45
  >0- < 50th (1.2 × 10-4 g – 5.7 × 10-1 g) 30/434 1.05 0.68, 1.61 1.15 0.75, 1.76
  0 62/968 1.00 Referent 1.00 Referent
Stillbirthb, d      
  Any 13/1,721 1.69 0.77, 3.68 1.67 0.76, 3.67
  ≥50th (5.7 × 10-1 g – 132 g) 9/859 2.39 1.02, 5.61 2.38 1.01, 5.59
  >0- < 50th (9.6 × 10-5 g – 5.7 × 10-1 g) 4/862 0.99 0.31, 3.17 0.98 0.30, 3.14
  0 14/3,115 1.00 Referent 1.00 Referent
  1. Abbreviations: CI confidence interval, GEE generalized estimating equation, LMP last menstrual period, PCE tetrachloroethylene, RR risk ratio, SGA small for gestational age.
  2. aModel for placental abruption adjusted for hypertension before or during pregnancy (yes, no) and first-trimester smoking (none, <11 cigarettes/day, ≥11 cigarettes/day). Model for preeclampsia adjusted for smoking and combined parity and previous ischemic placental disease (nulliparous, parous with no previous ischemic placental disease, parous with previous ischemic placental disease). Model for SGA adjusted for maternal age during LMP year (<25 y, 25–29.9 y, 30–34.9 y, 35+ y), year pregnancy ended (<1974, 1975–1980, and >1980), gestational weight gain <20 lb, hypertension before or during pregnancy, first-trimester smoking, and combined parity and previous ischemic placental disease. Model for stillbirth adjusted for first-trimester smoking.
  3. bAll live births and stillbirths ≥27 weeks gestation with non-missing data on covariates.
  4. cIndex live births with non-missing data on covariates.
  5. dStillbirth ≥27 weeks gestation.