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<h5 class="title" id="d448798e194">Background</h5>
<p id="P1">Urinary phthalate metabolites and psychosocial stress in pregnancy have
each been
associated with preterm birth (PTB), but no study has examined the joint impact of
these two environmental exposures. We hypothesized that there would be stronger associations
between phthalate exposure and PTB in mothers with higher stress in pregnancy compared
to mothers with lower stress.
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<h5 class="title" id="d448798e199">Methods</h5>
<p id="P2">We addressed this question using data from The Infant Development and the
Environment
Study (TIDES), a prospective birth cohort conducted at four US sites (N=783). We examined
urinary phthalate metabolite concentrations measured in samples collected from up
to three trimesters of pregnancy. Mothers reported their exposure to stressful life
events (SLE) in each trimester in a questionnaire administered in the third trimester.
PTB was defined as delivery before 37 weeks completed gestation (n=71, 9.1%). We examined
associations between urinary phthalate metabolite concentrations (individual time
points and on average) and PTB using logistic regression models adjusted for maternal
race, age, pre-pregnancy body mass index, education, specific gravity, and gestational
age at sample collection. In addition, we created models stratified by whether or
not mothers were exposed to any or no SLE in pregnancy.
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<h5 class="title" id="d448798e204">Results</h5>
<p id="P3">Summed di-2-ethylhexyl phthalate (ΣDEHP) metabolites measured in urine
samples from
the third trimester, but not the first trimester, were associated with an increased
odds ratio (OR) of PTB (OR=1.44, 95% confidence interval [CI]=1.06, 1.95). In models
stratified by SLE, associations between third trimester ΣDEHP concentrations and PTB
were significant only for women experiencing one or more SLE during pregnancy (OR
for ΣDEHP: 2.09, 95% CI: 1.29, 3.37) but not for women with no SLE during pregnancy
(OR for ΣDEHP: 1.04, 95% CI: 0.66, 1.63) (p for interaction=0.07).
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<h5 class="title" id="d448798e209">Conclusions</h5>
<p id="P4">We observed an association between urinary ΣDEHP levels and PTB that was
modified
by whether a mother was exposed to one or more psychosocial stressors during pregnancy.
Additional research to understand the joint impacts of chemical and non-chemical exposures,
with an emphasis on timing of exposure, is needed in order to advance the state of
the science on how the environment influences pregnancy.
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