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Table 2 Hazard ratios for maternal chronic kidney disease by history of preterm delivery, among women delivering between 1973 and 2012 in Sweden (n = 1,943,716)

From: Risk of long-term renal disease in women with a history of preterm delivery: a population-based cohort study

 Chronic kidney disease (N = 18,001)
nMinimally adjustedFully adjusted
HR (95% CI)HR (95% CI)
Exposure 1
 Term delivery (≥ 37 weeks)15,9141.01.0
 Preterm delivery (< 37 weeks)20871.47 (1.40–1.53)1.39 (1.32–1.45)
Exposure 2
 Term delivery (≥ 37 weeks)15,9141.01.0
 Moderate preterm delivery (32–36 + 6 weeks)17331.41 (1.34–1.48)1.35 (1.28–1.41)
 Very preterm delivery (28–31 + 6 weeks)2441.77 (1.56–2.01)1.55 (1.36–1.76)
 Extremely preterm delivery (< 28 weeks)1102.05 (1.70–2.48)1.84 (1.52–2.22)
Exposure 3
 Full term delivery (39–41 + 6 weeks)91341.01.0
 Post-term delivery (≥ 42 weeks)22370.94 (0.90–0.98)1.04 (0.99–1.09)
 Early term delivery (37–38 + 6 weeks)45431.13 (1.09–1.17)1.19 (1.15–1.24)
 Moderate preterm delivery (32–36 + 6 weeks)17331.44 (1.37–1.52)1.43 (1.36–1.51)
 Very preterm delivery (28–31 + 6 weeks)2441.81 (1.60–2.06)1.65 (1.45–1.87)
 Extremely preterm delivery (< 28 weeks)1102.11 (1.75–2.54)1.96 (1.63–2.37)
Exposure 4
 Term delivery (≥ 37 weeks)15,9141.01.0
 Spontaneous preterm delivery (< 37 weeks)15711.32 (1.25–1.39)1.32 (1.25–1.39)
 Iatrogenic preterm delivery—preeclampsia (< 37 weeks)2302.82 (2.48–3.21)2.81 (2.46–3.20)
 Iatrogenic preterm delivery—SGA (< 37 weeks)1821.74 (1.50–2.00)1.66 (1.44–1.93)
 Iatrogenic preterm delivery—preeclampsia and SGA (< 37 weeks)1042.11 (1.74–2.56)2.10 (1.73–2.55)
Exposure 5
 Two term deliveries (≥ 37 weeks)60131.01.0
 One preterm (< 37 weeks) and one term delivery (≥ 37 weeks)7231.51 (1.40–1.63)1.34 (1.24–1.45)
 Two preterm deliveries (< 37 weeks)931.67 (1.36–2.05)1.46 (1.19–1.79)
  1. Hazard ratios represent separate Cox regression models for associations between preterm delivery and maternal chronic kidney disease. Each exposure variable (1–5) represents different categories used to define gestational age at delivery. For all categories, preterm delivery was a time-dependent variable, where exposure status was based on the earliest gestation of any previous delivery. Minimally adjusted models controlled for year of delivery. Fully adjusted models controlled for year of delivery, maternal age, country of origin, education level, parity, inter-pregnancy interval, maternal BMI, smoking in pregnancy, exposure to gestational diabetes (time-dependent), and preeclampsia (time-dependent). In the analyses involving exposure 4 (spontaneous vs. iatrogenic preterm delivery), the models were not adjusted for preeclampsia. Abbreviations: CI confidence interval, HR hazard ratio, SGA small for gestational age