Abstract
BACKGROUND: Polycyclic aromatic hydrocarbons (PAHs) are formed during incomplete burning of fossil fuels, wood, and tobacco products. High PAH exposure has been associated with low birth weight, intrauterine growth restriction, and preterm birth, but little is known about its impact on adverse outcomes in early pregnancy such as in-utero fetal death. OBJECTIVES: To examine associations between exposure to PAHs and missed abortion in which the embryo has died but a miscarriage has not yet occurred during early pregnancy in a Chinese population in Tianjin. METHODS: A case-control study was conducted from April to November, 2007 in Tianjin, China. Cases experienced a missed abortion while controls underwent elective abortions before 14weeks of pregnancy. Eighty-one cases were recruited from four hospitals, with the same number of controls matched on hospital, maternal age (+/-8years), gravidity (1 or >1), and gestational age (+/-30days). Two maternal measures of PAH exposures were obtained based on benzo[a]pyrene (BaP) DNA adducts in 1) aborted tissues and 2) maternal blood (for a subset of subjects). In addition, proxy measures for PAH exposures from different sources were derived from maternal interviews. RESULTS: In conditional logistic regression analyses, we estimated more than 4-fold increase in risk of having experienced a missed abortion in women with above the median levels of blood BaP-DNA adducts (adjusted OR=4.27; 95% CI, 1.41-12.99); but no increase with adduct levels in aborted tissues (adjusted OR=0.76; 95% CI, 0.37-1.54). BaP-DNA adduct levels in maternal blood and aborted tissues were poorly correlated (r=-0.12; n=102). Missed abortion risk also was higher among women reporting traffic congestion near the residence, commuting by walking, and performing regular cooking activities during pregnancy. CONCLUSION: High levels of maternal PAH exposures may contribute to an increased risk of experiencing a missed abortion during early pregnancy.