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Table 2 Adjusted hazard ratios (HR) and 95% confidence intervals (CI’s) of pregnancy loss associated with drinking water nitrate exposure in pregnancy

From: Drinking water nitrate and risk of pregnancy loss: a nationwide cohort study

 

Pregnancy to week 22a

First trimesterb

Second trimesterc

 

n = 83,575 (2,915 pregnancy losses)

n = 53,082 (1,481 pregnancy losses)

n = 82,004 (1,352 pregnancy losses)

NO3- (mg/L)

Pregnancies (n (%))

Pregnancy losses (n)

aHRd (95% CI)

Pregnancies (n (%))

Pregnancy losses (n)

aHRd (95% CI)

Pregnancies (n (%))

Pregnancy losses (n)

aHRd (95% CI)

≤ 1

24,829 (29.7)

831

Ref (1)

15,428 (29.1%)

397

Ref (1)

24,717 (30.1)

423

Ref (1)

> 1- ≤ 2

23,474 (28.1)

829

0.97 (0.88, 1.07)

15,263 (28.8)

433

0.98 (0.86, 1.14)

22,894 (27.9)

363

0.91 (0.77, 1.06)

> 2- ≤ 5

22,013 (26.3)

781

1.00 (0.90, 1.10)

13,983 (26.3)

408

1.03 (0.89, 1.19)

21,492 (26.2)

351

0.95 (0.82, 1.10)

> 5- ≤ 25

9,586 (11.5)

346

1.04 (0.92, 1.18)

6,011 (11.3)

176

1.10 (0.92, 1.31)

9,229 (11.3)

156

0.98 (0.81, 1.17)

> 25

3,673 (4.4)

128

0.97 (0.81, 1.17)

2,397 (4.5)

67

1.03 (0.80, 1.34)

3,672 (4.5)

59

0.92 (0.70, 1.21)

  1. Model was fitted using robust standard error to control for non-independence of pregnancies by the same woman
  2. NO3- Nitrate concentration in drinking water, CI Confidence interval, Ref Reference
  3. a LMP to GA 21 weeks plus six days
  4. b LMP to GA 11 weeks plus six days
  5. c GA 12 weeks to GA 21 weeks plus six days
  6. d Adjusted for maternal age, education, occupation, population density, BMI, smoking and alcohol