. 2021 Feb 4;129(2):027002. doi: 10.1289/EHP7331

Table 4.

Effect modification of the associations between urbanicity and nitrate exposure on birth weight, body length at birth, head circumference at birth, and low birth weight.

	Birth weight (g)			Body length (mm)			Head circumference (mm)^a			Low birth weight
	$n = 852, 348$			$n = 848, 106$			$n = 588, 981$			$n = 852, 348$
	$n$	$Δ$ (95% CI)	$p$ -Value^b	$n$	$Δ$ (95% CI)	$p$ -Value^b	$n$	$Δ$ (95% CI)	$p$ -Value^b	$n$	OR (95% CI)	$p$ -Value^b
Rural areas^c	275,660	$- 7.3$ ( $- 13.8$ , $- 0.7$ )		274,406	$- 0.3$ ( $- 0.6$ , 0.002)		188,896	$- 0.2$ ( $- 0.5$ , 0.1)		275,660	0.93 (0.82, 1.06)
Provincial town^d	244,500	$- 15.1$ ( $- 23.0$ , $- 7.1$ )		243,189	$- 0.6$ ( $- 1.0$ , $- 0.2$ )		166,647	0.5 (0.2, 0.9)		244,500	1.15 (0.99, 1.34)
Provincial city^e	107,963	3.8 ( $- 5.8$ , 13.5)		107,405	$- 0.03$ ( $- 0.5$ , 0.4)		74,980	$- 0.1$ ( $- 0.5$ , 0.3)		107,963	0.95 (0.78, 1.16)
Suburb of capital	103,800	$- 32.7$ ( $- 52.4$ , $- 13.1$ )		103,286	$- 0.9$ ( $- 1.8$ , $- 0.001$ )		69,331	$- 0.4$ ( $- 1.2$ , 0.5)		103,800	1.20 (0.81, 1.77)
Capital	120,425	17.6 ( $- 23.3$ , 58.6)		119,820	4.2 (2.3, 6.1)		89,127	$- 2.4$ ( $- 4.3$ , $- 0.6$ )		120,425	1.14 (0.51, 2.55)
			0.002			$< 0.001$			0.001			0.20

Note: Models were fitted using linear regression with GLM and were controlled for maternal age, calendar year, sex, gravidity, maternal smoking, maternal education, maternal income, maternal employment status, region, and urbanicity. Models did not account for non-independence of observations for mothers with multiple births in the cohort. $Δ$ (95% CI) shown for exposures $x = 25.0 mg / L$ ${NO}_{3}^{-}$ compared to $0 mg / L$ . CI, confidence interval; GLM, generalized linear models; OR, odds ratio.

^{^a}

Data were available only for births in or after 1997.

^{^b}

p-Value from likelihood ratio tests comparing models with and without product interaction terms.

^{^c}

Municipalities in Denmark where the largest town has $< 10, 000$ inhabitants.

^{^d}

Municipalities where the largest town has between 10,000 and 100,000 inhabitants.

^{^e}

Municipalities where the largest town has $> 100, 000$ inhabitants.