Table 2

Air pollutant exposure and outcome definitions of studies included

SourceOutcomeDefinition of outcomeExposureDefinition of exposureExposure estimates
Choe et al12GDMBirth certificate data and ICD-9648.8x were listed, and absent otherwise.PM2.5, black carbonPM2.5 and black carbon from spatiotemporal models.Mean±SD
First trimester PM2.5: 9.7±1.9 µg/m3; second trimester PM2.5: 9.6±1.9 µg/m3
Third trimester PM2.5: 9.5±2.1 µg/m3; first trimester black carbon: 0.5±0.1 µg/m3; second trimester black carbon: 0.5±0.1 µg/m3; third trimester black carbon: 0.5±0.1 µg/m3
Fleisch et al13GDMFailed GCT(1) with ≥2 high values on the OGTT(2).PM2.5, black carbon, traffic exposurePM2.5 and black carbon from central sites within 40 km of residence.
PM2.5 and black carbon from spatiotemporal models.
Neighborhood traffic density [(vehicles/day) × km] within 100 m.
From central sites: PM2.5: 10.9±1.4 µg/m3; black carbon: 0.9±0.1 µg/m3
From spatiotemporal models: PM2.5: 11.9±1.4 µg/m3; black carbon: 0.7±0.2 µg/m3
Traffic density: 1621±2234 (vehicles/day × km)
Fleisch et al14GDMFailed GCT with ≥2 high values on the OGTT.PM2.5, traffic exposurePM2.5 from spatiotemporal models.
Neighborhood traffic density [(vehicles/day) × km] within 100 m.
First trimester PM2.5: 10.4±1.7 µg/m3; second trimester PM2.5: 10.4±1.7 µg/m3
Traffic density: 1317±2025 (vehicles/day × km)
Hu et al15GDMAccording to the American Diabetes Association 2003, failed GCT with ≥2 high values on the OGTT.PM2.5, O3Air pollution exposure data were obtained from the US EPA and CDC’s National Environmental Public Health Tracking Network (2003–2005) (US EPA 2014)Mean±SD
Trimester 1 PM2.5: 9.73±2.07 µg/m3; O3: 37.20±6.04 ppb
Trimester 2 PM2.5: 9.88±2.06 µg/m3; O3: 37.54±6.10 ppb
Full pregnancy PM2.5: 9.93±1.67 µg/m3; O3: 37.40±4.10 ppb
Lu et al16GDMA woman with a positive GCT and two or more abnormal 100 g OGTT values.PM2.5, SO2, NOx, CO, O3The exposure assessment of this study based on data from a single fixed-site monitoring station (Chiayi station).Mean±SD
3 months pre-pregnancy PM2.5: 44.38±12.09 µg/m3
First trimester PM2.5: 43.52±12.87 µg/m3; second trimester PM2.5: 41.20±13.43 µg/m3
Malmqvist et al17GDMGDM as defined in the Swedish Medical Birth Registry.NOx, traffic exposureMonthly and trimester means of NOx assigned by dispersion modeling at a spatial resolution of 500×500 m throughout the pregnancy.
Traffic density within a 200 m radius.
Quartiles of NOx exposure (μg/m3): Q1: 2.5–8.9; Q2: 9.0–14.1; Q3: 14.2–22.6; Q4: >22.7
Categories of traffic density within 200 m (vehicles/min): 1: no road; 2: <2; 3: 2–5; 4: 5–10; 5: >10
Pan et al18GDMAccording to the American Diabetes Association criteria, had two of the abnormal values on the OGTT.PM10, CO, NOx, SO2, O3Collected from 77 fixed-site air monitoring stations in Taiwan during 2004–2006.Mean±SD
PM10 (μg/m3): first trimester: 61.4±18.3; second trimester: 61.2±17.2; third trimester: 62.2±19.5
CO (ppm): first trimester: 0.6±0.1; second trimester: 0.6±0.1; third trimester: 0.6±0.2
NO (ppb): first trimester: 6.5±3.3; second trimester: 6.9±3.1; third trimester: 6.9±3.2
NO2 (ppb): First trimester: 20.2±5.3; second trimester: 19.8±5.5; third trimester: 19.1±5.9
NOx (ppb): first trimester: 26.6±7.8; second trimester: 26.5±7.8; third trimester: 25.7±8.2
SO2 (ppb): first trimester: 4.5±1.8; second trimester: 4.8±1.7; third trimester: 4.9±1.7
O3 (ppb): first trimester: 25.8±3.8; second trimester: 25.6±3.2; third trimester: 25.5±3.7
Pedersen et al19GDMSelf-reported, physician-diagnosed GDM.NO2, noise from road traffic (Lden) exposureNO2 was using the advanced AirGIS dispersion model. Road traffic noise was using SoundPLAN based on the Nordic prediction method.First trimester:NO2 (μg/m3): 11.5 (5.8, 27.4); road traffic noise (dB): 57.5 (49.3, 69.8); railway noise (dB): 51.3 (31.1, 68.6)
Robledo et al20GDMGDM was recorded in the medical record or discharge records (code 648.8) using the International Classification of Diseases, Ninth Revision.PM10, PM2.5, SO2, O3, CO, NOxUsing a modified Community Multiscale Air Quality (CMAQ) model version 4.7.1.IQR
Preconception PM2.5 (μg/m3): 5.54; PM10 (μg/m3): 6.3; SO2 (ppb): 3.30; NOx (ppb): 28.55; O3 (ppb): 12.33; CO (ppm): 0.26
First trimester PM2.5(μg/m3): 5.28; PM10 (μg/m3): 6.32; SO2 (ppb): 3.31; NOx (ppb): 30.21; O3 (ppb): 12.36; CO(ppm): 0.26
Shen et al21GDMInternational Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code: 648.0 or 648.8.PM10, PM2.5, SO2, O3, CO, NO2Collected from 76 fixed-site air quality monitoring stations supervised by the Taiwan Environmental Protection Agency during 2005–2013.
van den
Hooven et al
GDMGDM diagnosed according to the Dutch midwifery and obstetric guidelines.Traffic exposureDistance-weighted traffic density (DWTD) within a 150 m radius around residence (vehicles/24 hours × m); proximity to a major road (>10 000 vehicles/day).Median (P25–P75) DWTD (vehicles/24 hours × m): 5.5×105 (1.6×105−1.2×106)
Proximity to a major road (m): 140 (74–225)
Choe et al23GDMICD-9-CM code: 648.8.PM2.5, NO2Air pollution samples were collected at 150 monitoring sites in each of the four seasons for one 2-week session and in every 2 weeks at five reference locations to track city-wide temporal variation.Mean±SD
Trimester 1 PM2.5: 12.0±2.5 µg/m3; NO2: 27.9±6.3 ppb
Trimester 2 PM2.5: 11.9±2.4 µg/m3; O3: 27.9±6.3 ppb
Jo et al24GDMBased on laboratory values confirming a plasma glucose level of 200 mg/dL or higher on the glucose challenge test or at least two plasma glucose values meeting or exceeding the following values on the 100 or 75 g oral glucose tolerance test.PM2.5, PM10, NO2, O3Distance-weighted monthly average from four closest monitoring stations within 50 km, except for geocoded locations within 0.25 km of a monitor.Mean±SD
PM2.5: 18.2±5.5 µg/m3; PM10: 38.4±10.9 µg/m3; NO2: 25.8±8.2 ppb; O3: 41.3±7.6 ppb
  • (1) Glucose change test: serum glucose 1 hour after a non-fasting 50 g oral glucose load. (2) Oral glucose tolerance test: serum glucose 3 hours after a fasting 100 g glucose load.

  • CDC, Centers for Disease Control and Prevention; CO, carbon monoxide; EPA, Environmental Protection Agency; GCT, glucose change test; GDM, gestational diabetes mellitus; NO, nitric oxide; NO2, nitrogen dioxide; NOx, nitrogen oxide; O3, ozone; OGTT, oral glucose tolerance test; PM10, particulate matter ≤10 μm in diameter; PM2.5, particulate matter ≤2.5 μm in diameter; SO2, sulfur dioxide.