Ha, E H; Lee, B E; Park, H; Lee, J T; Hong, Y C; Kim, Y J; Kim, Y S; Kim, H

Objectives: Although there have been growing concerns about the adverse effects of air pollution on preterm birth, little is known about whether air pollutants contribute to preterm birth. This study aims to evaluate the association between prenatal exposure to air pollutants and preterm birth.

Methods: We obtained birth data in Seoul between January 1, 1998 and December 31, 2000 from the Korean National Birth Register. The last menstrual period and ultrasound assessment were used to estimate gestational age. Preterm birth was defined as less than 37 weeks completed gestation. Using the air pollution data, we estimated the exposure during each trimester and also during each month of pregnancy on the basis of the gestational age and birth date of each newborn. Both of logistic regression analysis in SAS and generalized additive logistic regression analyses in SPLUS were conducted considering infant sex and order, parental age, marriage status, parity, live birth, maternal occupation, educational level of father and season.

Results: Using logistic regression model, the adjusted odds ratio (AOR) of an interquartile range (IQR) of PM10 for preterm birth was 1.06 (95% CI, 0.97-1.15) in third trimester. The highest risk for PM10 was observed in 7 month (OR = 1.07, 95% CI = 1.01-1.14). The monthly analyses suggested that the risks for preterm birth tended to increase with PM10 exposure between the sixth and ninth months of pregnancy. Using generalized additive model (GAM), we observed similar results with logistic regression model. However, the effect size from GAM was larger than that from logistic regression.

Conclusions: We found that prenatal exposure to PM10 was associated with preterm birth. The monthly analyses suggested that exposure to PM10 during mid to late pregnancy contributes to risks for preterm birth.

(C) 2003 Lippincott Williams & Wilkins, Inc.