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Table 2 Association between individual exposure to ambient NO2 in different time periods during pregnancy and anthropometric measures at birth.*

From: Air pollution exposure during pregnancy and reduced birth size: a prospective birth cohort study in Valencia, Spain

 

Birth weight (in g)a

(n:785)

Birth length (in cm)a

(n:784)

Birth head circumference (in cm)a

(n:782)

NO2 exposure period

β

(95% CI)

Linearity (df)b

β

(95% CI)

Linearity (df)b

β

(95% CI)

Linearity (df)b

Unadjusted

         

First trimester

-3.564

(-23.698;16.570)

L

-0.092

(-0.177;-0.008)

NL (4)

-0.069

(-0.133;-0.004)

L

Second trimester

-4.464

(-25.175;16.248)

NL (3)

-0.050

(-0.137;0.037)

NL (2)

-0.071

(-0.137;-0.004)

L

Third trimester

-5.740

(-26.553;15.072)

L

-0.010

(-0.096;0.077)

NL (4)

-0.017

(-0.084;0.049)

L

Whole pregnancy

-5.792

(-30.065;18.481)

NL (3)

-0.063

(-0.165;0.038)

L

-0.074

(-0.152;0.003)

L

Adjusted c

         

First trimester

-12.782

(-34.537;8.972)

NL (3)

-0.066

(-0.149;0.017)

NL (4)

-0.066

(-0.137;0.005)

L

Second trimester

-9.961

(-32.594;12.671)

NL (4)

-0.040

(-0.125;0.044)

NL (3)

-0.060

(-0.133;0.014)

NL (3)

Third trimester

-4.294

(-25.923;17.335)

L

-0.005

(-0.089;0.079)

NL (2)

-0.028

(-0.099;0.042)

L

Whole pregnancy

-9.729

(-33.218;13.760)

L

-0.047

(-0.146;0.052)

NL(2)

-0.058

(-0.134;0.018)

NL (3)

  1. * Estimates are expressed as the change in birth anthropometric measures for a 10 μg/m3 increase in the mean NO2 levels at each woman's residence during the corresponding period. Unadjusted and adjusted models.
  2. a Standardized for gestational age.
  3. b Shape of the relationship after contrast between model with NO2 in non-linear vs. linear form; L: linear; NL: non-linear (and degrees of freedom of the selected model).
  4. c Adjusted for:
  5. -Birth weight = maternal age, maternal pre-pregnancy weight, maternal height, paternal height, gestational weight gain, parity, maternal education, smoking during pregnancy, country of origin, sex of the infant, and season of last menstrual period.
  6. -Birth length = maternal age, maternal height, gestational weight gain, parity, maternal education, smoking during pregnancy, working status in the first trimester, country of origin, and sex of the infant.
  7. -Birth head circumference: maternal age, maternal pre-pregnancy weight, maternal height, gestational weight gain, parity, maternal education, smoking during pregnancy, country of origin, sex of the infant, and season of last menstrual period.