Is The Prenatal Urine Inorganic Arsenic Concentration A Factor Related To Low Birth Weight? A Cohort Study In Arica, Chile

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Background: Despite the fact that previous studies have examined the association between birth weight and arsenic pollution, few studies have examined the association between prenatal exposure to low-level inorganic arsenic (iAs) and birth weight. In the 1980s, the region of Arica in Chile became contaminated with toxic smelting waste containing arsenic. iAs is known to persistent in the environment. We examined the association between prenatal maternal iAs exposure and newborn birth weight. Methods: This was a cohort study of pregnant women attending in primary health care centers in Arica during 2013. Socio-demographic information as well as information related to arsenic exposure was obtained through an interviewer-based at the time of recruitment. Urine samples were collected during second trimester to assess iAs levels. Birth weight was obtained from birth records. We used multiple linear regression to relate birth weight to inorganic As levels, adjusting for potential confounders: socioeconomical position, mother's age, sex, BMI, gestational age, wedlock and tobacco use during pregnancy. Results: 257 pregnant women were recruited, 242 gave the urine sample and to date we have collected birth weight data of 229 newborns. iAs levels were a positively skewed distributed with a median of 14 and IQR=12.3 μg/L. Birth weight's distribution was negative biased with a median of 3350 and IQR=480 grams. Prenatal iAs exposure was not associated with birth weight (βadj =4.79, 95% CI: -2.28-11.87) even when the model was adjusted for confounders. No clear dose-response trends were evident. Conclusion: In our sample birth weight was not associated with iAs exposure but it was associated with mother's age and gestational age, which is consistent with previous studies. These results could be due to low levels of exposure in this group of pregnant women. This finding differs in the literature in that other studies examine populations exposed to high levels of iAs.