Supplemental Digital Content

(1)

Supplemental Digital Content

Interaction of air pollutants and meteorological factors on birth weight in Shenzhen, China

eTable 1- eTable8

eTable 1. The yearly concentration of air pollutants among monitors

Year Monitor ID PM10 (µg/m³) SO2 (µg/m³) NO2 (µg/m³)

Mean SD Mean SD Mean SD

2005 1 57.8 30.4 19.3 14 36.2 16.0

2 62.3 32.0 16.7 8.3 31.1 13.7

3 60.2 28.2 20.5 8.8 44.3 19.5

4 65.3 35.5 19.3 11.5 36.1 14.6

5 65.1 31.1 25.2 17.3 40.5 17.1

6 66.3 34.2 22.6 12.0 37.4 18.2

2006 1 61.2 31.8 26.9 16.6 52.6 21.8

2 64.9 32.4 23.7 14.4 49.2 20.1

3 61.4 27.2 28.5 13.1 54.4 23.3

4 67.4 34.2 28.7 17.3 49.1 24.6

5 65.9 29.7 36.3 21.5 50.6 22.2

6 70.7 35.2 32.1 17.3 56.8 24.5

2007 1 62.2 32.9 21.4 13.2 50.9 20.4

2 64.2 31.7 21.3 10.8 46.6 19.4

3 60.5 30.4 23.6 11.8 52.7 22.1

4 66.3 34.9 22.7 14.7 53.3 22.0

5 64.7 32.3 30.5 21.4 54.9 22.4

6 71.7 37.3 26.9 13.5 57.6 23.5

2008 1 61.1 34.1 16.6 11.2 53.7 25.1

2 64.9 33.9 13.8 9.2 38.0 24.5

3 56.5 30.5 17.3 9.2 47.6 23.2

4 62.8 33.7 15.7 11.0 45.5 27.6

5 61.6 31.7 19.7 14.9 48.7 22.4

6 70.3 37.0 20.6 12.0 54.5 26.6

7 71.1 31.0 10.7 7.9 38.6 19.1

8 81.9 38.7 18.8 7.8 41.7 20.5

2009 1 53.7 29.5 11.5 7.6 50.1 21.8

2 56.0 29.7 11.8 6.9 47.7 19.5

3 51.6 26.9 9.6 7.0 41.3 17.9

4 56.3 31.4 12.3 8.9 43.2 19.8

(2)

5 54.2 29.5 15.5 11.8 44.7 24.7

6 58.4 33.9 19.9 13.4 45.3 24.3

7 60.2 28.1 8.6 3.8 27.7 17.8

8 65.6 31.3 13.7 5.9 38.6 16.3

2010 1 56.3 42.5 8.8 6.6 46.0 23.0

2 57.6 42.4 7.9 5.8 49.8 27.5

3 52.9 37.7 10.8 6.9 42.3 20.8

4 54.5 36.6 9.6 8.1 51.2 27.0

5 54.3 40.3 12.3 11.4 46.6 33.1

6 57.0 44.0 12.6 9.3 51.0 33.1

7 60.6 42.4 11.9 7.3 36.9 23.5

8 65.4 41.7 14.4 5.1 35.4 16.7

2011 1 55.7 29.6 9.5 6.6 44.2 19.1

2 56.7 30.6 10.0 6.7 52.7 23.9

3 55.3 29.2 6.4 5.6 49.5 18.4

4 53.6 29.8 10.6 7.4 53.5 23.6

5 62.7 38.5 14.0 9.6 50.2 25.4

6 61.3 35.7 12.9 8.6 58.6 31.1

7 55.4 25.9 12.0 5.8 42.2 22.7

8 56.3 29.3 11.3 6.8 34.5 15.6

2012 1 46.3 26.1 6.7 4.2 40.1 16.4

2 50.5 26.0 7.1 3.6 46.1 16.5

3 47.0 25.2 5.9 3.8 39.8 15.2

4 48.5 25.8 8.4 4.7 43.6 15.9

5 64.7 34.9 9.7 6.7 46.4 18.0

6 54.4 32.3 9.1 6.4 42.8 19.6

7 54.6 25.9 16.7 7.5 43.7 20.4

8 42.1 30.1 6.6 4.4 25.2 15.6

(3)

eTable 2. Correlation of air pollutant concentrations among monitors

Monitor ID

PM10 (µg/m³) SO2 (µg/m³) NO2 (µg/m³)

2 3 4 5 6 7 8 2 3 4 5 6 7 8 2 3 4 5 6 7 8

1 0.94 0.94 0.92 0.88 0.91 0.85 0.78 0.75 0.79 0.74 0.76 0.72 0.26 0.69 0.82 0.76 0.79 0.82 0.77 0.67 0.72 2 1.00 0.93 0.91 0.89 0.91 0.85 0.81 1.00 0.80 0.75 0.68 0.75 0.23 0.60 1.00 0.70 0.79 0.78 0.76 0.74 0.67

3 1.00 0.9 0.89 0.9 0.86 0.75 1.00 0.77 0.76 0.75 0.28 0.64 1.00 0.67 0.71 0.66 0.73 0.67

4 1.00 0.90 0.93 0.80 0.78 1.00 0.77 0.77 0.22 0.49 1.00 0.86 0.83 0.67 0.57

5 1.00 0.93 0.78 0.70 1.00 0.78 0.18 0.50 1.00 0.86 0.72 0.57

6 1.00 0.82 0.79 1.00 0.15 0.58 1.00 0.64 0.56

7 1.00 0.79 1.00 0.11 1.00 0.59

(4)

eTable 3. Gestational age of subjects

Gestational age (weeks) SGA, (n, %) Non-SGA, (n, %) TLBW, (n, %) Non-TLBW, (n, %)

26 11 (0.0) 37 (0.0) - -

27 10 (0.0) 115 (0.0) - -

28 65 (0.1) 984 (0.1) - -

29 67 (0.1) 1193 (0.1) - -

30 149 (0.2) 1677 (0.2) - -

31 192 (0.2) 2246 (0.2) - -

32 354 (0.4) 3232 (0.3) - -

33 599 (0.6) 4477 (0.4) - -

34 992 (1.1) 7495 (0.7) - -

35 2631 (2.8) 12459 (1.1) - -

36 3974 (4.3) 25215 (2.3) - -

37 10186 (10.9) 80747 (7.3) 7740 (36.6) 83603 (7.5)

38 18438 (19.7) 209475 (18.9) 6052 (28.6) 222781 (20) 39 24487 (26.2) 333862 (30.2) 4167 (19.7) 355492 (31.8) 40 22562 (24.1) 278897 (25.2) 2261 (10.7) 300290 (26.9)

41 7421 (7.9) 122633 (11.1) 715 (3.4) 129715 (11.6)

42 1240 (1.3) 18816 (1.7) 156 (0.7) 19959 (1.8)

43 195 (0.2) 3536 (0.3) 43 (0.2) 3700 (0.3)

44 - - 15 (0.1) 945 (0.1)

a: SGA: small for gestational age; TLBW: term low birth weight

(5)

eTable 4. Multicollinearity assessment for multi-pollutant models

Gestational period

Dependent variables

Air pollutants in models ^a

Air pollutant for VIF assessment ^b

VIF

1^st trimester Birthweight PM10 PM10 1.40

PM10, NO2 PM10 2.65

NO2 2.51

PM10, NO2, SO2 PM10 3.01

NO2 2.60

SO2 1.60

2^nd trimester Birthweight PM10 PM10 1.07

PM10, NO2 PM10 3.61

NO2 3.40

PM10, NO2, SO2 PM10 3.86

NO2 3.45

SO2 1.55

3^rd trimester Birthweight PM10 PM10 1.71

PM10, NO2 PM10 3.58

NO2 3.39

PM10, NO2, SO2 PM10 3.86

NO2 3.61

SO2 1.65

Entire pregnancy

Birthweight PM10 PM10 1.10

PM10, NO2 PM10 2.08

NO2 1.92

PM10, NO2, SO2 PM10 3.05

NO2 1.92

SO2 2.01

a: All models were adjusted for covariates, including gestational age, maternal age, maternal education level, parity, season of conception, number of prenatal examinations, pre-pregnancy BMI, preeclampsia

b: VIF: variance inflation factor

(6)

eTable 5. Association between air pollutants and SGA/TLBW by gestational period

Air pollutants

Trimester specific IQR IQR of the entire pregnancy SGA

OR (95%CI)^a

TLBW OR (95%CI)^a

SGA

OR (95%CI)^b

TLBW OR (95%CI)^b PM10

1^st trimester 1.05 (1.04-1.07) 1.09 (1.07-1.12) 1.03 (1.02-1.03) 1.04 (1.03-1.05) 2^nd trimester 1.01 (0.99-1.02) 1.03 (1.01-1.05) 1.002 (1.00-1.01) 1.01 (1.00-1.02) 3^rd trimester 0.99 (0.97-1.01) 1.01 (0.97-1.06) 0.99 (0.98-1.00) 1.00 (0.98-1.03) Entire pregnancy 1.00 (0.99-1.01) 1.03 (1.01-1.06) 1.00 (0.99-1.01) 1.03 (1.01-1.06) NO2

1^st trimester 1.03 (1.02-1.04) 1.05 (1.02-1.07) 1.02 (1.01-1.02) 1.02 (1.01-1.04) 2^nd trimester 1.01 (1.00-1.02) 1.03 (1.01-1.05) 1.01 (1.00-1.01) 1.02 (1.01-1.03) 3^rd trimester 0.99 (0.98-1.01) 0.98 (0.95-1.02) 1.00 (0.99-1.01) 0.99 (0.97-1.01) Entire pregnancy 1.00 (0.99-1.01) 1.01 (0.99-1.03) 1.00 (0.99-1.01) 1.01 (0.99-1.03) SO2

1^st trimester 0.99 (0.98-1.00) 1.00 (0.98-1.03) 0.996 (0.99-1.0) 1.00 (0.98-1.02) 2^nd trimester 0.99 (0.98-1.00) 1.00 (0.98-1.02) 0.99 (0.98-1.00) 1.00 (0.98-1.02) 3^rd trimester 0.99 (0.98-1.00) 1.00 (0.98-1.02) 0.99 (0.98-1.00) 1.01 (0.98-1.03) Entire pregnancy 0.99 (0.97-1.00) 0.99 (0.96-1.01) 0.99 (0.97-1.00) 0.99 (0.96-1.01)

a: ORs were calculated for trimester specific IQR increase in each pollutant (PM10: the 1^st trimester: 23.1 µg/m³, the 2^nd trimester: 23.3 µg/m³, the third trimester: 24.2 µg/m³, the entire pregnancy: 11.1 µg/m³; NO2: the 1^st trimester: 15.1 µg/m³, the 2^nd trimester: 13.4 µg/m³, the third trimester: 13.5 µg/m³, the entire pregnancy: 7.8 µg/m³; SO2: the 1^st trimester: 11.3 µg/m³, the 2^nd trimester: 10.0 µg/m³, the third trimester: 9.3 µg/m³, the entire pregnancy: 10.7 µg/m³).

b: ORs were calculated for per IQR increase in each pollutant during the entire pregnancy (11.1 µg/m³for PM10, 7.8 µg/m³for NO2, and 10.7 µg/m³for SO2).

All models were adjusted for covariates, including gestational age, maternal age, maternal education level, parity, season of conception, number of prenatal examinations, pre-pregnancy BMI, and preeclampsia.

(7)

eTable 6. Association between air pollutants and SGA/TLBW by gestational period

Air pollutants

Vaginal births Cesarean birth

SGA

OR (95%CI)^a

TLBW OR (95%CI)^a

SGA

OR (95%CI)^a

TLBW OR (95%CI)^a PM10

1^st trimester 1.05 (1.03-1.06) 1.07 (1.03-1.10) 1.07 (1.05-1.09) 1.12 (1.08-1.16) 2^nd trimester 1.00 (0.98-1.01) 1.00 (0.97-1.03) 1.02 (1.00-1.04) 1.05 (1.02-1.09) 3^rd trimester 1.01 (0.99-1.04) 1.03 (0.97-1.09) 0.97 (0.93-1.02) 1.01 (0.95-1.08) Entire pregnancy 1.00 (0.98-1.01) 1.01 (0.98-1.04) 1.01 (0.99-1.03) 1.05 (1.02-1.09) NO2

1^st trimester 1.02 (1.01-1.04) 1.04 (1.00-1.07) 1.04 (1.02-1.06) 1.05 (1.01-1.09) 2^nd trimester 1.00 (0.99-1.01) 1.00 (0.98-1.03) 1.02 (1.01-1.04) 1.05 (1.02-1.08) 3^rd trimester 1.01 (0.99-1.03) 1.01 (0.99-1.04) 0.98 (0.96-1.01) 0.99 (0.94-1.04) Entire pregnancy 1.00 (0.99-1.01) 1.00 (0.97-1.02) 1.01 (0.99-1.02) 1.02 (0.99-1.05) SO₂

1^st trimester 1.00 (0.99-1.02) 0.99 (0.96-1.02) 1.00 (0.99-1.02) 1.02 (0.99-1.06) 2^nd trimester 1.00 (0.99-1.01) 0.99 (0.96-1.01) 0.99 (0.98-1.01) 1.01 (0.98-1.05) 3^rd trimester 1.01 (0.99-1.02) 0.98 (0.95-1.00) 0.99 (0.97-1.00) 0.96 (0.94-0.99) Entire pregnancy 1.00 (0.98-1.01) 0.98 (0.95-1.01) 0.99 (0.97-1.01) 1.00 (0.97-1.04)

a: ORs were calculated for per interquartile increase in each pollutant, and all models were adjusted for covariates, including gestational age, maternal age, maternal education level, parity, season of conception, number of prenatal examinations, pre-pregnancy BMI, and preeclampsia.

(8)

eTable 7. Association between SO

2

and SGA/TLBW after excluding the data of the seventh monitor

Gestational period IQR (µg/m³) SGA OR (95%CI)^a TLBW OR (95%CI)^a 1^st trimester 11.98 1.01 (1.00-1.02) 1.00 (0.98-1.03) 2^nd trimester 11.75 0.99 (0.98-1.00) 0.99 (0.97-1.02) 3^rd trimester 11.62 0.99 (0.98-1.00) 1.01 (0.98-1.03) Entire pregnancy 12.04 0.99 (0.97-0.99) 0.98 (0.96-1.01)

a: ORs were calculated for per interquartile increase in each pollutant, and all models were adjusted for covariates, including gestational age, maternal age, maternal education level, parity, season of conception, number of prenatal examinations, pre-pregnancy BMI, and preeclampsia.

(9)

eTable 8. Association between air pollution exposure during the entire pregnancy and TLBW/SGA by meteorological factor categories

(conception in cold season: November-April)

Air pollutants

Meteorological factor categories^a

Interaction P-value

<5^th percentile OR (95%CI)^b

5^th -95^th percentile OR (95%CI)^b

>95^thpercentile OR (95%CI)^b Air temperature

SGA

PM10 0.97 (0.76-1.24) 0.95 (0.90-1.00) 1.10 (0.83-1.46) 0.14 NO2 0.94 (0.86-1.03) 1.02 (1.00-1.05) 1.03 (0.92-1.16) 0.66 SO2 0.93 (0.73-1.18) 0.98 (0.93-1.03) 1.09 (0.88-1.35) 0.55 TLBW

PM10 0.84 (0.39-1.82) 1.01 (0.90-1.13) 0.64 (0.31-1.29) 0.35 NO2 1.02 (0.77-1.37) 1.03 (0.98-1.07) 0.81 (0.61-1.07) 0.40 SO2 1.17 (0.52-2.64) 0.96 (0.86-1.06) 1.21 (0.76-1.94) 0.33

Dew point temperature SGA

PM10 0.96 (0.80-1.15) 0.93 (0.88-0.98) 0.93 (0.68-1.27) 0.05 NO2 0.94 (0.88-1.00) 1.02 (1.00-1.04) 1.03 (0.94-1.12) 0.74 SO2 0.79 (0.62-1.01) 0.999 (0.95-1.05) 1.04 (0.80-1.36) 0.22 TLBW

PM10 1.96 (0.74-5.16) 0.99 (0.89-1.10) 1.52 (0.68-3.37) 0.02 NO2 0.81 (0.53-1.22) 1.02 (0.98-1.06) 1.03 (0.85-1.24) 0.07 SO2 0.50 (0.17-1.49) 0.97 (0.88-1.08) 0.98 (0.51-1.88) 0.13

a: Both air temperature and dew point temperature were classified as three categories: <5^th percentile, 5^th -95^th percentile, and >95^th percentile.

b: ORs were calculated for per interquartile increase in each pollutant (11.1 µg/m³for PM10, 7.8 µg/m³for NO2, and 10.7 µg/m³for SO2). All models were adjusted for covariates, including gestational age, maternal age, maternal education level, parity, number of prenatal examinations, pre-pregnancy BMI, and preeclampsia.