Urinary Phthalate Metabolites in Relation to Preterm Birth in Mexico City

Abstract

BackgroundRates of preterm birth have been rising over the past several decades. Factors contributing to this trend remain largely unclear, and exposure to environmental contaminants may play a role.ObjectiveWe investigated the relationship between phthalate exposure and preterm birth.MethodsWithin a large Mexican birth cohort study, we compared third-trimester urinary phthalate metabolite concentrations in 30 women who delivered preterm (< 37 weeks of gestation) with those of 30 controls (≥ 37 weeks of gestation).ResultsConcentrations of most of the metabolites were similar to those reported among U.S. females, although in the present study mono-n-butyl phthalate (MBP) concentrations were higher and monobenzyl phthalate (MBzP) concentrations lower. In a crude comparison before correcting for urinary dilution, geometric mean urinary concentrations were higher for the phthalate metabolites MBP, MBzP, mono(3-carboxylpropyl) phthalate, and four metabolites of di(2-ethyl-hexyl) phthalate among women who subsequently delivered preterm. These differences remained, but were somewhat lessened, after correction by specific gravity or creatinine. In multivariate logistic regression analysis adjusted for potential confounders, elevated odds of having phthalate metabolite concentrations above the median level were found.ConclusionsWe found that phthalate exposure is prevalent among this group of pregnant women in Mexico and that some phthalates may be associated with preterm birth.

Effect of environmental phthalate exposure on pregnancy duration and birth outcomes

“…The total daily intake of DEHP was 108.5 μg/day and DEP -176.5 μg/day; which is close to the values calculated based on the same model by Koch et al (2003) [46]. It needs to be pointed that in majority of the studies in this field, the assessment of exposure was based on phthalate levels in urine collected, as in our study, during the third trimester of pregnancy [11,13,16,17] or in cord blood [4][5][6]. Additionally, the recently published study by in which phthalate metabolites were measured 4 times in pregnancy period, has indicated that urinary phthalate metabolite levels showed moderate individual and population-wide variability during pregnancy, and that most of them demonstrated a slightly downward sloping trend across gestation [14].…”

“…Results of the studies of the impact of phthalates on pregnancy duration are not consistent. In the studies that measured phthalate metabolite levels in cord blood or, similarly as in our study, in the urine collected in the third trimester of pregnancy, 4 noted significant associations with shortened pregnancy duration or increased odds of preterm birth [4,6,16,17], while 2 other studies indicated longer gestation with an increase in concentrations of phthalate metabolites (which as suggested by Wolff et al (2009) can result from residual confounding) [11,13]. No association was noted by Suzuki et al (2010) [10].…”

“…However, the studies evaluating the impact of phthalate exposure on duration of pregnancy are not consistent. Some of them have indicated no effect [10] and other a decreased [4,6,[14][15][16][17] as well as increased gestational age [11,13]. In addition, in some studies [10,12] no association between phthalate exposure and birth outcomes has been observed, whereas in otherstatistically significant positive [11] and negative associations have been reported [5,6].…”

“…Birth outcomes, such as birth weight, have been frequently used for evaluation of fetal development and have been indicated to predict occurrence of diseases and neurodevelopment delay later in life [7][8][9]. Several studies on the effects of prenatal phthalate exposure on pregnancy duration and birth outcomes have been published [4][5][6][10][11][12][13][14][15][16][17]. However, the studies evaluating the impact of phthalate exposure on duration of pregnancy are not consistent.…”

Early-life risk factors for chronic nonrespiratory diseases

“…Furthermore, there appear to be relationships of environmental toxins with birth at lower gestational age, and phthalates [55,56] and perfluorinated compounds [51,53] with preterm birth.…”