A register-based study of the association between air pollutants and hypertensive disorders in pregnancy among the Japanese population.
BACKGROUND
Ambient air pollution is hypothesized to be a risk factor for hypertensive disorders in pregnancy, one of the major pregnancy complications. Past studies have reported the supporting evidence, however this mainly referred to the Western population, and results from trimester-specific analysis have been varied. In this study, we focused on exposure during the first trimester of pregnancy (placental development stage), and tested the hypothesis among the Japanese population.


METHODS
We drew on data from the Japan Perinatal Registry Network database, and studied 36,620 singleton pregnant women without medical complications, in western Japan (Kyushu and Okinawa districts) between 2005 and 2010. In addition, data on ozone, suspended particulate matter (SPM), nitrogen dioxide (NO2), and sulfur dioxide (SO2) concentrations were obtained. The nearest monitoring station to the respective birthing hospital was used as a reference point for assigning average concentrations of each pollutant during the first trimester of pregnancy for each woman. The logistic regression model was applied to assess the association between quintiles of each pollutant and hypertensive disorders in pregnancy.


RESULTS
Mean concentrations during the first trimester were 41.3 ppb for ozone, 27.4 μg/m(3) for SPM, 11.8 ppb for NO2, and 3.2 ppb for SO2. High exposure to ozone was associated with an increased risk of hypertensive disorders in pregnancy (for highest quintile vs. lowest: odds ratio=1.20, 95% confidence interval=1.01-1.42). With regard to SPM, NO2 and SO2, we did not obtain the results with constant directionality.


CONCLUSIONS
Ozone exposure during early pregnancy may be a risk factor for hypertensive disorders in pregnancy.
Environmental Epidemiology Section, Center for Environmental Health Sciences, National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan. Electronic address: tmichikawa@nies.go.jp.
Takehiro
T
Michikawa
Department of Obstetrics and Gynecology, Kyushu University Hospital, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Seiichi
S
Morokuma
Department of Obstetrics, Fukuoka Children's Hospital, 5-1-1 Kashiiteriha, Higashi-ku, Fukuoka 813-0017, Japan.
Kotaro
K
Fukushima
Environmental Epidemiology Section, Center for Environmental Health Sciences, National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan; Graduate School of Engineering, Kyoto University, Katsura, Sakyo-ku, Kyoto 615-8530, Japan.
Kayo
K
Ueda
Environmental Epidemiology Section, Center for Environmental Health Sciences, National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan; Preventive Medicine and Public Health, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
Ayano
A
Takeuchi
Department of Obstetrics and Gynecology, Kyushu University Hospital, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Kiyoko
K
Kato
Environmental Epidemiology Section, Center for Environmental Health Sciences, National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan.
Hiroshi
H
Nitta
D000328:Adult; D000393:Air Pollutants / Q000633:toxicity*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000139:chemically induced* / Q000150:complications; D007564:Japan; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000139:chemically induced*; D012042:Registries
D000393:Air Pollutants
First trimester; Hypertensive disorders in pregnancy; Japan; Ozone; Register-based