Abstract
Objectives
To examine the relation between prenatal urinary phthalate metabolite concentrations and preterm birth (PTB).
Methods
The data were drawn from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study, a pan-Canadian cohort of 1857 pregnant women enrolled between 2008 and 2011. We quantified urinary concentrations of 7 phthalate metabolites that were detected in > 70% of urine samples collected during the first trimester. Gestational age was obtained from either the last menstrual period or early ultrasound. We used Cox proportional hazard models to examine the associations of urinary phthalate metabolite concentrations, plus the molar sum of di-2-ethylhexyl phthalate metabolites (∑DEHP), with time to delivery before 37 weeks of gestation. We also examined PTB by clinical presentation. PTBs presented with either spontaneous labour or premature rupture of the membrane were considered spontaneous PTB (sPTB). Additionally, we used multiple linear regression to model changes in mean gestational age in relation to phthalate exposure.
Results
We found no evidence of an association between first trimester phthalate metabolite concentrations and PTB among the MIREC study participants. For example, each 2-fold increase in any of the 7 phthalate concentrations or ∑DEHP was associated with hazard ratios (HRs) for PTB ranging from 0.95 to 1.07 with 95% confidence intervals including the null. An assessment of non-linear trends showed some evidence of non-monotonic dose-response relationships between phthalates and PTB. Furthermore, male infants exposed to MCPP showed higher sPTB risk compared with female infants.
Conclusion
Phthalate exposure during early pregnancy is not clearly associated with the risk of PTB among this Canadian population.
Résumé
Objectifs
Examiner la relation entre les concentrations prénatales des métabolites urinaires des phtalates et les naissances avant terme (NAT).
Méthode
Les données proviennent de l’Étude mère-enfant sur les composés chimiques de l’environnement (MIREC), une étude de cohorte pancanadienne de 1 857 femmes enceintes inscrites entre 2008 et 2011. Nous avons chiffré les concentrations urinaires de 7 métabolites phtaliques détectés dans > 70 % des échantillons d’urine prélevés au cours du premier trimestre. L’âge gestationnel a été obtenu d’après la date des dernières menstruations ou d’une échographie précoce. Nous avons utilisé le modèle à risques proportionnels de Cox pour examiner les associations entre les concentrations des métabolites urinaires des phtalates, plus la somme des moles des métabolites phtaliques de bis(2-éthylhexyle) (∑DEHP), et une date d’accouchement avant 37 semaines de grossesse. Nous avons aussi examiné les NAT selon leur tableau clinique. Les NAT se présentant avec un travail spontané ou avec la rupture prématurée des membranes ont été considérées comme étant spontanées (NATs). De plus, nous avons procédé par régression linéaire multiple pour modéliser les changements de l’âge gestationnel moyen en lien avec l’exposition aux phtalates.
Résultats
Nous n’avons relevé aucun signe d’association entre les concentrations en métabolites phtaliques au premier trimestre et les NAT chez les participantes de l’étude MIREC. Par exemple, chaque multiplication par deux de l’une des 7 concentrations de phtalates ou de la ∑DEHP était associée à des coefficients de danger de NAT allant de 0,95 à 1,07 avec des intervalles de confiance de 95 % incluant les valeurs nulles. Une évaluation des tendances non linéaires a montré des signes de relations dose-réponses non monotones entre les phtalates et les NAT. De plus, les nourrissons de sexe masculin exposés aux phtalates de mono(3-carboxypropyle) (MCPP) présentaient un risque de NATs plus élevé que les nourrissons de sexe féminin.
Conclusion
L’exposition aux phtalates en début de grossesse n’est pas clairement associée au risque de naissance avant terme dans cette population canadienne.
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Acknowledgements
We are grateful to all the participants who took part in the MIREC Study, as well as to all study staff.
Funding
This project was funded by a Catalyst Grant from the Canadian Institutes of Health Research (L-CIP-150736). The MIREC Study was funded by Health Canada’s Chemicals Management Plan, the Ontario Ministry of the Environment and a research grant from the Canadian Institutes of Health Research (MOP-81285).
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Health Canada and the Institutional Review Boards of CHU Sainte-Justine Research Centre and Simon Fraser University approved the MIREC Study. All participants gave their informed consent to participate in the study.
Competing interests
JMB was financially compensated for serving as an expert witness for plaintiffs in litigation related to tobacco smoke exposures.
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Hu, J.M.Y., Arbuckle, T.E., Janssen, P. et al. Associations of prenatal urinary phthalate exposure with preterm birth: the Maternal-Infant Research on Environmental Chemicals (MIREC) Study. Can J Public Health 111, 333–341 (2020). https://doi.org/10.17269/s41997-020-00322-5
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Keywords
- Preterm birth
- Gestational age
- Phthalates
- Environmental chemicals
Mots-clés
- Naissance avant terme
- Âge gestationnel
- Phtalates
- Produits chimiques dans l’environnement