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Table 2 Characteristics of the study population in relation to the gestational age at delivery

From: Kuopio birth cohort – design of a Finnish joint research effort for identification of environmental and lifestyle risk factors for the wellbeing of the mother and the newborn child

  Total newborn
n = 1172
Preterm birth
< 37 GWS
n = 81 (6.9)
Term birth
37–40 GWS
n = 855 (73.0)
Late-term birth
≥41 GWS
n = 236 (20.1)
Birth weight, g 3446 ± 597 2156 ± 704 3497 ± 470 3701 ± 395
 1st tertile ≤3280   79 (20) 218 (56) 94 (24)
 2nd tertile 3281-3700   2 (0.5) 166 (43) 223 (57)
 3rd tertile ≥3701   0 (0) 131 (34) 259 (66)
Placental weighta, g 590 ± 130 439 ± 117 592 ± 125 620 ± 124
 1st tertile ≤530   51 (13) 179 (47) 155 (40)
 2nd tertile 531–630   8 (2.1) 179 (47) 196 (51)
 3rd tertile ≥631   2 (0.5) 145 (39) 225 (61)
Maternal ageb, years 29.8 ± 5.1 30.7 ± 5.4 29.9 ± 5.0 29.4 ± 5.3
 1st tertile ≤28   21 (4.6) 203 (44) 233 (51)
 2nd tertile 29–32   28 (7.4) 161 (43) 188 (50)
 3rd tertile ≥33   22 (6.8) 145 (45) 155 (48)
Number of previous deliveriesb 1.0 ± 1.3 0.7 ± 1.1 1.1 ± 1.3 0.7 ± 1.1
 Nulliparous   45 (8.8) 210 (41) 258 (50)
 Primiparous   14 (3.9) 159 (44) 186 (52)
 Multiparous   12 (4.2) 140 (49) 132 (47)
Number of twin pregnancies 16 (1.4) 10 (63) 6 (38) 0 (0)
Gestational week at delivery, weeksb 39.2 ± 2.0 33.5 ± 3.2 39.1 ± 0.9 41.1 ± 0.3
Foetal sex, males 589 (50.3) 42 (51.9) 443 (51.8) 104 (44.1)
Self-reported smoking before pregnancy 226 (20)    
Number of daily cigarettes before pregnancyb
 No smoking 957 (80) 60 (6.3) 715 (75) 182 (19)
 1–10 135 (11.7) 4 (3.0) 93 (69) 38 (28)
  ≥ 11 64 (5.5) 7 (11) 41 (64) 16 (25)
Self-reported smoking during pregnancy 49 (4.2)    
Number of daily cigarettes during pregnancyb
 No smoking 1104 (96) 68 (6.2) 811 (74) 225 (20)
 1–5 28 (2.4) 1 (3.6) 22 (79) 5 (18)
  ≥ 6 24 (2.1) 2 (8.3) 16 (67) 6 (25)
Self-reported alcohol consumption before pregnancyb, weekly doses (average)
 None 601 (52) 27 (4.5) 468 (78) 106 (18)
 1–5 497 (43) 40 (8.0) 343 (69) 114 (23)
  ≥ 6 58 (5.0) 4 (6.9) 38 (66) 16 (28)
Self-reported alcohol consumption during pregnancyb, monthly (average)
 Never 1053 (96) 66 (6.3) 172 (73) 215 (20)
 Less than once 36 (3.3) 12 (2.8) 23 (64) 12 (33)
 Once a month, and more 11 (1.0) 1 (9.1) 9 (82) 1 (9.1)
  1. Values are n (%) or mean ± SD
  2. aExcluded twin pregnancies, n = 16
  3. bmothers with twin pregnancies included only once, total n = 1156 gestational weeks (GWS)