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  • Variability in urinary phthalate metabolite levels across pregnancy and sensitive windows of exposure for the risk of preterm birth.

Variability in urinary phthalate metabolite levels across pregnancy and sensitive windows of exposure for the risk of preterm birth.

Environment international (2014-06-18)
Kelly K Ferguson, Thomas F McElrath, Yi-An Ko, Bhramar Mukherjee, John D Meeker
ABSTRACT

Preterm birth is a significant public health problem, affecting over 1 in 10 live births and contributing largely to infant mortality and morbidity. Everyday exposure to environmental chemicals such as phthalates could contribute to prematurity, and may be modifiable. In the present study we examine variability in phthalate exposure across gestation and identify windows of susceptibility for the relationship with preterm birth. Women were recruited early in pregnancy as part of a prospective, longitudinal birth cohort at the Brigham and Women's Hospital in Boston, Massachusetts. Urine samples were collected at up to 4 time points during gestation for phthalate measurement, and birth outcomes were recorded at delivery. From this population we selected all 130 cases of preterm birth, defined as delivery before 37 weeks of completed gestation, as well as 352 random controls. Urinary phthalate metabolite levels were moderately variable over pregnancy, but levels measured at multiple time points were associated with increased odds of preterm birth. Adjusted odds ratios (aOR) for spontaneous preterm birth were strongest in association with phthalate metabolite concentrations measured at the beginning of the third trimester (aOR for summed di-2-ethylhexyl phthalate metabolites [∑DEHP]=1.33, 95% confidence interval [CI]=1.02, 1.73). Odds ratios for placental preterm birth, defined as delivery with presentation of preeclampsia or intrauterine growth restriction, were slightly elevated in the first trimester for DEHP metabolites (aOR for ∑DEHP=1.33, 95% CI=0.99, 1.78). Pregnant women with exposure to phthalates both early and late in pregnancy are at an increased risk of delivering preterm, but mechanisms may differ based on etiology.

MATERIALS
Product Number
Brand
Product Description

Supelco
Bis(2-ethylhexyl) phthalate, PESTANAL®, analytical standard
Sigma-Aldrich
Phthalic acid, ACS reagent, ≥99.5%
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Bis(2-ethylhexyl) phthalate, Selectophore
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Bis(2-ethylhexyl) phthalate, certified reference material, TraceCERT®, Manufactured by: Sigma-Aldrich Production GmbH, Switzerland
Phthalic acid, European Pharmacopoeia (EP) Reference Standard
Plastic additive 01, European Pharmacopoeia (EP) Reference Standard
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Dioctyl phthalate, ≥99.5%
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Phthalic acid, puriss. p.a., ≥99.5% (T)
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Bis(2-ethylhexyl) phthalate solution, certified reference material, 2000 μg/mL in methanol
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Potassium hydrogen phthalate, BioXtra, ≥99.95%
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Potassium phthalate monobasic, puriss. p.a., ≥99.5% (T)
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Potassium phthalate monobasic, BioUltra, ≥99.5% (T)
Supelco
Potassium phthalate monobasic, reference material for titrimetry, certified by BAM, ≥99.5%
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Potassium phthalate monobasic, Standard for quantitative NMR, TraceCERT®, Manufactured by: Sigma-Aldrich Production GmbH, Switzerland
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Sigma-Aldrich
Phthalic acid dipotassium salt, 98%