Table 1 Maternal and perinatal background characteristics of the study groups

Age, y

30 (26/33)

33 (30/38)

29 (25/32)

31 (28/35)

0.020

<0.001

Body mass index, kg/m²

23.6 (21.2/27.3) [985]

24.8 (22.1/29.4) [351]

23.0 (21.0/25.7)

22.8 (20.7/26.2)

0.006

<0.001

Highest systolic blood pressure, mmHg

165 (153/178)

166 (156/180)

126 (119/134)

124 (117/131)

<0.001

<0.001

Highest diastolic blood pressure, mmHg

109 (104/116)

109 (103/116)

83 (78/88)

81 (77/86)

<0.001

<0.001

Highest proteinuria, g/24 h

3.1 (1.4/6.2) [887]

2.9 (1.1/5.6) [305]

1.0 (0.8/1.6) [4]

0.6 [2]

N/A

N/A

Smoking before pregnancy

172 (18.3) [941]

48 (14.6) [328]

90 (24.8) [363]

44 (14.5) [304]

0.008

0.954

Smoking during pregnancy

58 (6.1) [948]

26 (7.8) [333]

28 (7.5) [371]

26 (8.4) [308]

0.345

0.769

Chronic hypertension

151 (15.3)

85 (24.1)

…

…

…

…

Gestational diabetes mellitus

116 (11.8)

69 (19.6)

29 (7.7)

24 (7.5)

0.030

<0.001

Pregestational diabetes mellitus

24 (2.4)

16 (4.5)

4 (1.1)

1 (0.3)

0.136

<0.001

Placental weight, g

495 (400/600) [951]

500 (390/615) [338]

590 (500/669) [363]

628 (554/720) [314]

<0.001

<0.001

Placental insufficiency

94 (9.5)

50 (14.2)

…

…

…

…

Gestational age at birth, weeks

37.9 (35.4/39.3) [986]

37.4 (34.6/39.0)

40.6 (39.6/41.3)

40.3 (39.4/41.1)

<0.001

<0.001

Birth weight, g

2775 (2185/3280)

2790 (1882/3384)

3520 (3245/3851)

3730 (3416/4022)

<0.001

<0.001

Relative birth weight (SD)

−1.1 (−1.9/−0.4) [986]

−1.1 (−1.9/0.0) [350]

−0.2 (−0.7/0.5)

0.3 (−0.3/0.9)

<0.001

<0.001