title: Small for gestational age and exposure to particulate air pollution in the early-life environment of twins.
abstract: Several studies in singletons have shown that maternal exposure to ambient air pollutants is associated with restricted fetal growth. About half of twins have low birth weight compared with six percent in singletons. So far, no studies have investigated maternal air pollution exposure in association with birth weight and small for gestational age in twins. We examined 4760 twins of the East Flanders Prospective Twins Survey (2002-2013), to study the association between in utero exposure to air pollution with birth weight and small for gestational age. Maternal particulate air pollution (PM10) and nitric dioxide (NO2) exposure was estimated using a spatial temporal interpolation method over various time windows during pregnancy. In the total group of twins, we observed that higher PM10 and NO2 exposure during the third trimester was significantly associated with a lower birth weight and higher risk of small for gestational age. However, the association was driven by moderate to late preterm twins (32-36 weeks of gestation). In these twins born between 32 and 36 weeks of gestation, birth weight decreased by 40.2g (95% CI: -69.0 to -11.3; p=0.006) and by 27.3g (95% CI: -52.9 to -1.7; p=0.04) in association for each 10µg/m³ increment in PM10 and NO2 concentration during the third trimester. The corresponding odds ratio for small for gestational age were 1.68 (95% CI: 1.27-2.33; p=0.0003) and 1.51 (95% CI: 1.18-1.95; p=0.001) for PM10 or NO2, respectively. No associations between air pollution and birth weight or small for gestational age were observed among term born twins. Finally, in all twins, we found that for each 10µg/m³ increase in PM10 during the last month of pregnancy the within-pair birth weight difference increased by 19.6g (95% CI: 3.7-35.4; p=0.02). Assuming causality, an achievement of a 10µg/m³ decrease of particulate air pollution may account for a reduction by 40% in small for gestational age, in twins born moderate to late preterm.
authors.affiliation: Centre for Environmental Sciences, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium; Department of Complex Genetics, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
authors.forename: Esmée M
authors.initials: EM
authors.lastname: Bijnens
authors.affiliation: Centre of Human Genetics, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium; Department of Obstetrics and Gynaecology, Ghent University Hospitals, 9000, Ghent, Belgium.
authors.forename: Catherine
authors.initials: C
authors.lastname: Derom
authors.affiliation: Department of Complex Genetics, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
authors.forename: Marij
authors.initials: M
authors.lastname: Gielen
authors.affiliation: Centre for Environmental Sciences, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium.
authors.forename: Ellen
authors.initials: E
authors.lastname: Winckelmans
authors.affiliation: Belgian Interregional Environment Agency, Kunstlaan 10-12, 1210 Brussel, Belgium.
authors.forename: Frans
authors.initials: F
authors.lastname: Fierens
authors.affiliation: Centre of Human Genetics, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Robert
authors.initials: R
authors.lastname: Vlietinck
authors.affiliation: Department of Complex Genetics, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
authors.forename: Maurice P
authors.initials: MP
authors.lastname: Zeegers
authors.affiliation: Centre for Environmental Sciences, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium; Department of Public Health, Leuven University (KU Leuven), Kapucijnenvoer 35, 3000 Leuven, Belgium. Electronic address: tim.nawrot@uhasselt.be.
authors.forename: Tim S
authors.initials: TS
authors.lastname: Nawrot
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000032:analysis; D000397:Air Pollution / Q000032:analysis*; D001530:Belgium / Q000453:epidemiology; D001724:Birth Weight; D005260:Female; D005865:Gestational Age; D006801:Humans; D008297:Male; D018811:Maternal Exposure; D009585:Nitrogen Dioxide / Q000032:analysis; D052638:Particulate Matter / Q000032:analysis; D011247:Pregnancy; D014427:Twins; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D009585:Nitrogen Dioxide
keywords: Air pollution; Birth weight; Particulate matter; Pregnancy; Small for gestational age; Twin