[Retracted] Exposure to Ambient Air Pollutant PM₁₀ in the Second Trimester of Pregnancy Is Associated with Preterm Birth: A Birth-Based Health Information Cohort Study

Table 1

Maternal and fetal characteristics in the birth cohort.

Characteristic	Data
Maternal
Age,
Gestational age (wk),
Parity, no. (%)
1	2857 (54.3)
2	2250 (42.8)
≥3	150 (2.9)
Year of conception, no. (%)
2015	1686 (31.9)
2016	3605 (68.1)
Season of conception, no. (%)
Spring	1265 (23.9)
Summer	1043 (19.7)
Autumn	1613 (30.5)
Winter	1370 (25.9)
Mode of delivery, no. (%)
Vaginal	5063 (95.7)
Cesarean	228 (4.3)
Preeclampsia, no. (%)	173 (3.3)
Diabetes, no. (%)	642 (12.1)
Maternal obesity, no. (%)	140 (2.6)
Maternal anemia, no. (%)	2147 (40.6)
History of cesarean section, no. (%)	1009 (19.1)
Infant
Birth weight (g),
Sex of infant, no. (%)
Male	2495 (47.1)
Female	2296 (43.4)
Missing	500(9.5)
Term birth, no. (%)	4829 (91.3%)
PTB, no. (%)	462 (8.7)
Moderate or , <259	409 (7.7)
VPTB	52 (1.0)
ExPTB	1 (0)
Mean concentration of PM10 (μg/m^3),
First trimester
Second trimester
Third trimester
Entire pregnancy
PM10 exposure during the second trimester (%)
<60 μg/m^3	4154 (78.5)
≥60 μg/m^3	1137 (21.5)

PM₁₀: particulate matter with ; PTB: preterm birth; VPTB: very preterm birth; ExPTB: extremely preterm birth. Dichotomous variables are presented as percent of total for each characteristic.