The Effect of Environmental Carbon Monoxide Pollution on Spontaneous Abortion of the First Trimester of Pregnancy in Tehran

Air pollution is the major problem in industrial cities. It seriously threatens the inhabitants'' health، especially high-risk people like pregnant women’s. Spontaneous abortion could happen as a consequence of carbon monoxide in this situation. This study was aimed to examining the effect of environmental carbon monoxide concentration on the rate of spontaneous abortion. This study was conducted on 148 pregnant women who had spontaneous abortion (case group) and 148 pregnant women without abortion (control group). They were collected randomly from 10 hospitals in different area of Tehran between June 2010 to February 2011 and the correlation between spontaneous abortion and environmental carbon monoxide was investigated. Two groups were matched by their age، their husbands'' age، age at the first childbirth، educational level، average of family income، previous delivery type، interval between deliveries، history of previous abortion، body mass index، parity، duration of residence in Tehran and the amount of time spent at work and outside of the home (P>0. 05). The study revealed that the mean of environmental carbon monoxide concentration in case group (4. 09±2. 09PPM) was significantly higher than control group (2. 81±1/07PPM) (P<0. 001) and the rate of abortion was 1. 98 times higher in highly concentrated areas (CI95% 1. 55-2. 53). There was also a negative relationship between gestational age and carbon monoxide concentration. The results of the study showed that there was a significant relationship between the occurrence of spontaneous abortion and the environmental carbon monoxide concentration.