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Table 1 Characteristics of participants

From: Maternal exposure to ambient fine particulate matter and risk of premature rupture of membranes in Wuhan, Central China: a cohort study

CharacteristicsAll Births
(N = 4364)
PROM
(N = 511)
PPROM
(N = 102)
Mode of delivery
 Vaginal3267 (74.9%)396 (77.5%)88 (86.3%)
 Cesarean1097 (25.1%)115 (22.5%)14 (13.7%)
Year of birth
 20151674 (38.3%)210 (41.1%)49 (48.0%)
 20161540 (35.3%)185 (36.2%)39 (38.2%)
 20171150 (26.4%)116 (22.7%)14 (13.7%)
Season of conceptiona
 Spring976 (22.4%)115 (22.5%)22 (21.6%)
 Summer1001 (22.9%)115 (22.5%)22 (21.6%)
 Autumn1158 (26.5%)122 (23.9%)26 (25.5%)
 Winter1229 (28.2%)159 (31.1%)32 (31.4%)
Maternal age26.7 ± 3.626.6 ± 3.526.3 ± 3.6
Maternal age group
 18–1966 (1.5%)7 (1.4%)4 (3.9%)
 20–241212 (27.8%)135 (26.4%)25 (24.5%)
 25–292129 (48.8%)272 (53.2%)56 (54.9%)
 30–35957 (21.9%)97 (19.0%)17 (16.7%)
Parity
 03751 (85.9%)467 (91.4%)96 (94.1%)
  ≥ 1613 (14.1%)44 (8.6%)6 (5.9%)
Maternal anemia
 No4045 (92.7%)474 (92.8%)95 (93.1%)
 Yes319 (7.31%)37 (7.2%)7 (6.9%)
Maternal preeclampsia
 No4308 (98.7%)490 (95.9%)90 (88.2%)
 Yes56 (1.3%)21 (4.1%)12 (11.8%)
Maternal gestational diabetes
 No4175 (95.7%)502 (98.2%)101 (99.0%)
 Yes189 (4.3%)9 (1.8%)1 (1.0%)
History of obstetrical-gynecological pathologyb
 No4173 (95.6%)493 (96.5%)100 (98.0%)
 Yes191 (4.4%)18 (3.5%)2 (2.0%)
Mean temperature across the whole pregnancy (°C)18.0 ± 2.318.0 ± 2.318.0 ± 2.4
Mean concentration of PM2.5 in the 1st trimester (μg/m3)63.7 (47.6–85.6)64.4 (50.9–84.5)65.3 (53.2–86.9)
Mean concentration of PM2.5 in the 2nd trimester (μg/m3)59.3 (41.7–81.4)59.2 (41.8–81.0)59.5 (42.0–82.3)
Mean concentration of PM2.5 in the 3rd trimester (μg/m3)55.8 (39. 9–73.8)55.0 (40.1–79.0)59.2 (43.7–79.0)
Mean concentration of PM2.5 across the whole pregnancy (μg/m3)61.8 (55.4–67.8)62.7 (55.8–68.0)65.9 (56.2–70.5)
  1. Data are expressed in N (%) or mean ± SD or Median (interquartile range)
  2. PROM Premature rupture of membranes, PPROM Preterm premature rupture of membranes
  3. aSpring: March to May; Summer: June to August; Autumn: September to November; Winter: December to February
  4. bIncluding chorioamnionitis, uterine myoma, adnexal cyst, pelvic infection, pelvic pathologic adhesion, pelvicellulitis, cervicitis, vaginal bleeding during pregnancy, and/or colpomycosis