Environmental Carbon Monoxide Related to Pregnancy Hypertension

Abstract

Carbon monoxide pollution frequently occurs due to auto exhaust, industrial emissions, and/or cigarette smoke. Exogenous and endogenous carbon monoxide affects blood pressure; however, the relation of carbon monoxide exposure to pregnancy hypertension has not been systematically examined. For the present study the authors recruited a total of 2,707 apparently healthy, non-obese, non-smoking mothers, aged between 15 and 40 years, who had singleton births, and who lived within two miles of the selected air monitoring stations in Tehran, Iran, to study the relation of ambient carbon monoxide to pregnancy hypertension (>140 mmHg systolic and/or >90 mmHg diastolic after the 20th week of gestation). A relatively small but statistically significant elevation in mean postpartum diastolic blood pressure (mean ± SD, 69.5 ± 9.8 mmHg) was observed in the mothers' who were exposed to relatively high ambient carbon monoxide (mean = 14.1 ppm) compared to mothers exposed to lower carbon monoxide (mean = 1.8 ppm) concentrations (mean ± SD, 68.0 ± 8.3 mmHg, p < 0.01). The authors found twice the rate of pregnancy hypertension in the relatively higher carbon monoxide exposed mothers than the mothers with lower exposure (adjusted odds ratio = 2.02, 95% CI 1.35–3.03). Findings of the present study suggest that high level ambient carbon monoxide exposure is associated with pregnancy hypertension.

KEYWORDS:

• carbon monoxide
• women
• pregnancy hypertension
• air-pollution
• environmental exposure

Notes

This study was supported by Tehran University of Medical Sciences from design to collecting data and the Japanese National Institute of Occupational Safety and Health for writing the paper and submission.

*Lowest CO exposure; yearly average of 1.8 ppm.

**Highest CO exposure; yearly average of 14.1 ppm.

*>140 mmHg systolic and/or >90 mmHg diastolic.

^†Mean ± standard division; Student t-test.

^‡Number of yes answer and percentage in parenthesis; Chi-square test.

^§One-year mean (daily range): 1.8 (0.7–2.7 ppm).

^#One-year mean (daily range): 14.1 (5.4–19.6 ppm).