Table 4.

Relationships between hypothyroidism during pregnancy and exposure to PM_2.5 and PM₁₀ in Changping District

	PM2.5		PM10
	OR	P	OR	P
250 m buffer
Pre-LMPM 90 days	1.012(0.973–1.052)	0.561	1.005(0.973–1.037)	0.771
Pre-LMPM 60 days	1.052(1.012–1.093)	0.009*	1.042(1.009–1.075)	0.011*
Pre-LMPM 30 days	1.070(1.029–1.113)	< 0.001*	1.053(1.019–1.090)	0.002*
LMPM	1.139(1.088–1.194)	< 0.001*	1.100(1.060–1.141)	< 0.001*
Post-LMPM 30 days	1.038(0.995–1.083)	0.086	1.025(0.990–1.060)	0.160
Post-LMPM 60 days	1.008(0.971–1.047)	0.666	1.006(0.975–1.038)	0.702
Post-LMPM 90 days	1.038(0.996–1.082)	0.072	1.030(0.997–1.065)	0.077
500 m buffer
Pre-LMPM 90 days	1.012(0.973–1.053)	0.538	1.005(0.973–1.038)	0.769
Pre-LMPM 60 days	1.052(1.013–1.093)	0.009*	1.042(1.009–1.075)	0.012*
Pre-LMPM 30 days	1.070(1.029–1.113)	< 0.001*	1.054(1.019–1.090)	0.002*
LMPM	1.140(1.088–1.195)	< 0.001*	1.099(1.059–1.141)	< 0.001*
Post-LMPM 30 days	1.038(0.994–1.083)	0.090	1.025(0.990–1.060)	0.164
Post-LMPM 60 days	1.008(0.970–1.047)	0.670	1.006(0.975–1.038)	0.702
Post-LMPM 90 days	1.038(0.996–1.082)	0.072	1.030(0.996–1.065)	0.080
750 m buffer
Pre-LMPM 90 days	1.013(0.973–1.053)	0.532	1.005(0.973–1.038)	0.772
Pre-LMPM 60 days	1.053(1.013–1.094)	0.009*	1.042(1.009–1.075)	0.012*
Pre-LMPM 30 days	1.071(1.029–1.114)	< 0.001*	1.053(1.018–1.089)	0.003*
LMPM	1.140(1.088–1.196)	< 0.001*	1.099(1.059–1.140)	< 0.001*
Post-LMPM 30 days	1.037(0.994–1.083)	0.094	1.024(0.990–1.060)	0.171
Post-LMPM 60 days	1.008(0.970–1.047)	0.685	1.006(0.974–1.038)	0.722
Post-LMPM 90 days	1.038(0.996–1.082)	0.078	1.030(0.996–1.065)	0.085

LMPM: last menstrual period month.; OR (95% CI): odds ratio (95% confidence interval). OR values represent the increased risk of hypothyroidism per 10 µg/m³ of ambient particulate matter exposure. *P < 0.05. All logistic regression models were adjusted for age, the season of the last menstruation, and pregnancy and delivery history