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Table 4 Unadjusted and adjusted odds ratios (ORs) of SGA ( n = 30,443) among the total population of singleton live births ( n = 1,007,977) for the years 1991–2010 in Finland

From: Contribution of socioeconomic status to the risk of small for gestational age infants – a population-based study of 1,390,165 singleton live births in Finland

Characteristic/risk factors

Unadjusted OR

Adjusted OR

Maternal age (years)

  

≤19

1

1

20-29

0.63 (0.60–0.67)

1.08 (1.04–1.18)**

30-39

0.62 (0.59–0.65)

1.37 (1.28–1.46)***

≥40

0.87 (0.81–0.94)

1.82 (1.66–1.99)***

Primiparity

2.20 (2.15–2.24)

2.41 (2.33-2.48)***

Gestational age (weeks)

  

<28

7.30 (6.70–7.95)

6.26 (5.65–6.93)***

28 − 31 + 6

7.35 (6.85–7.89)

5.90 (5.43–6.40)***

32 − 36 + 6

3.17 (3.06–3.28)

2.74 (2.63–2.84)***

37 − 39 + 6

1

1

40 − 41 + 6

0.59 (0.58–0.61)

0.59 (0.58–0.61)***

>42

0.51 (0.47–0.54)

0.44 (0.41–0.47)***

Pregravid BMIa

  

≤24.9

1.32 (1.24–1.41)

1.38 (1.28–1.48)***

25-29.9

1.00 (0.93–1.08)

1.06 (0.98–1.15)

≥30

1

1

Smoking status

  

Non-smoking

1

1

Quitted smoking

1.28 (1.20 − 1.36)

1.07 (1.00 − 1.15)*

Smoking

2.45 (2.39–2.51)

2.34 (2.28–2.42)***

Single marital status

1.58 (1.51–1.64)

1.09 (1.04–1.15)***

Socioeconomic status (SES)

  

Upper white-collar workers

1

1

Lower white-collar workers

1.16 (1.11–1.21)

1.11 (1.06–1.17)***

Blue-collar workers

1.42 (1.35–1.49)

1.24 (1.17–1.30)***

Other

1.19 (1.14–1.25)

1.13 (1.07–1.19)***

Missing

1.36 (1.29 − 1.43)

1.15 (1.08 − 1.21)***

Prior pregnancies (number)

0.88 (0.87–0.89)

0.98 (0.97–0.99)***

Prior terminations (number)

1.11 (1.08–1.13)

1.00 (0.97–1.03)

IVFb

1.19 (1.07–1.32)

0.83 (0.74–0.92)***

Chorionic villus biopsy

1.22 (1.11–1.34)

1.08 (0.97–1.21)

Amniocentesis

1.44 (1.37–1.51)

1.30 (1.23–1.38)***

Placenta previa

1.47 (1.23–1.75)

0.75 (0.61–0.91)**

Placental abruption

3.36 (2.94–3.83)

1.41 (1.22–1.64)***

Major congenital anomaly

3.19 (3.08–3.32)

2.51 (2.40–2.62)***

Prior Cesarean section

0.89 (0.86–0.93)

1.26 (1.21–1.29)***

Time periods

  

1991 − 1996

1

1

1997 − 2001

1.05 (1.02 − 1.08)

1.04 (1.00 − 1.07)*

2002 − 2006

1.07 (1.04 − 1.10)

1.08 (1.04 − 1.11)***

2007 − 2010

1.14 (1.11 − 1.18)

1.17 (1.13 − 1.21)***

Place of residence grouped by hospital districts

  

1

1.40 (1.27 − 1.53)

1.29 (1.17 − 1.42)***

2

1

1

3

1.29 (1.17 − 1.43)

1.20 (1.08 − 1.34)***

4

1.38 (1.29 − 1.47)

1.21 (1.13 − 1.30)***

5

1.64 (1.44 − 1.86)

1.51 (1.32 − 1.73)***

6

1.45 (1.31 − 1.61)

1.38 (1.24 − 1.54)***

7

1.36 (1.25 − 1.48)

1.18 (1.08 − 1.30)***

8

1.13 (1.02 − 1.26)

1.17 (1.05 − 1.32)**

9

1.19 (1.10 − 1.28)

1.11 (1.02 − 1.21)*

10

1.35 (1.24 − 1.47)

1.21(1.10 − 1.32)***

11

1.66 (1.52 − 1.81)

1.54 (1.40 − 1.70)***

12

1.31 (1.17 − 1.46)

1.13 (1.00 − 1.28)*

13

1.14 (1.06 − 1.23)

1.05 (0.97 − 1.14)

14

1.33 (1.22 − 1.45)

1.27 (1.16 − 1.40)***

15

1.31 (1.22 − 1.54)

1.32 (1.22 − 1.42)***

16

1.43 (1.32 − 1.54)

1.34 (1.23 − 1.45)***

17

1.35 (1.25 − 1.47)

1.21(1.11 − 1.32)***

18

1.15 (1.06 − 1.25)

1.04 (0.96 − 1.14)

19

1.02 (0.93 − 1.11)

1.00 (0.91 − 1.10)

20

1.15 (1.07 − 1.23)

0.97 (0.89 − 1.05)

  1. SGA = small for gestational age, aBody mass index (BMI), data cover the years 2004–2010, *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001.