Table 1.

Epidemiological studies of associations between air pollution exposure during pregnancy and ultrasound measures of fetal parameters

Reference	Study location	Number of women	Number of ultrasound measurements	Time period of ultrasound measurements	Fetal parameters evaluateda	Air pollutantsb	Air pollutant exposure windows	Summary of key results	Additional covariatesc
[25]	France	366	2 per pregnancy	Second and third trimester	HC	NO2	Fertilization – trimester ultrasound exam	Decreases in HC were associated with the highest tertile of NO2 exposure	Parity, gestational diabetes, and maternity center
[26]	Australia	14 734	1–3 per pregnancy	13–26 weeks of gestation	HC, AC, FL, and BPD	O3, NO2, SO2, and PM10	Monthly; first 4 months of pregnancy	Negative associations between early exposures to pollutants and mean changes in growth parameters during mid-gestation (13–26 weeks)	Concurrent temperature exposures, and seasonality and long-term trend
[27]	France	271	2–3 per pregnancy	Second and third trimester	HC and BPD	Benzene	7 day sampling period	Reductions in BPD and HC associated with log transformed exposures of benzene in second and third trimesters	Urinary cotinine levels, birth order, occupational exposure to paints or pesticides, month of conception, maternal age at end of studies, and center
[28]	Sabadell, Spain	562	1 per pregnancy	12, 20, and 32 weeks of gestation	HC, AC, and BPD	NO2 and BTEX	LMP until 12, 20, and 32 weeks; 12–20 and 20–32 week averages	Exposure during weeks 1–12 was negatively associated with BPD growth in weeks 20–32	Season of conception, parity
[29▪▪]	Netherlands	7772	3 per pregnancy	First, second and third trimester	HC and FL	NO2 and PM10	Conception – trimester ultrasound exam	NO2 and PM10 exposures during pregnancy were inversely associated with HC and FL at various stages of gestation.	Parity, folic acid supplementation use, alcohol consumption, paternal height, and road traffic noise exposure
[30▪▪]	Valencia, Spain	785	3 per pregnancy	12, 20, and 32 weeks of gestation	BPD, AC, and FL	NO2	0–12, 12–20, 20–32, 32–delivery; 0–20 and 0–32 week avg.	Adverse effects on fetal parameters were higher in association with NO2 exposure in earlier stages of pregnancy	Maternal gestational weight gain, country of origin, zone of residence, parity, alcohol, caffeine, vegetable, fruit and energy intake and season of conception

LMP, last menstrual period.

^aFetal parameters: head circumference (HC), abdominal circumference (AC), femur length (FL), and biparietal diameter (BPD).

^bAir pollutants: nitrogen dioxide (NO₂), ozone (O₃), sulfur dioxide (SO₂), particulate matter less than 10 μm aerodynamic diameter (PM₁₀), and benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene compounds (BTEX).

^cCommon covariates included maternal age, smoking, SES measures, weight/BMI, and fetal sex.