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Table 1 Characteristics of women with spontaneous singleton births by early pregnancy body mass index, n = 29,709

From: Early pregnancy body mass index and spontaneous preterm birth in Northwest Russia: a registry-based study

Characteristics

Underweight

Normal

Overweight

Obese

p*

 

n = 2,100

n = 20,081

n = 5,427

n = 2,101

 

Age at delivery, mean (SD)

24.2 (4.1)

26.4 (4.8)

28.4 (5.2)

29.4 (5.0)

<0.001

Age at delivery, n (%)

    

<0.001

 ≤ 19

239 (11.4)

1,257 (6.3)

167 (3.1)

29 (1.4)

 20-24

965 (46.0)

6,510 (32.4)

1,230 (22.7)

345 (16.4)

 25-29

668 (31.8)

7,214 (35.9)

1,812 (33.4)

703 (33.5)

 30-34

191 (9.1)

3,874 (19.3)

1,485 (27.4)

670 (31.9)

 ≥35

37 (1.8)

1,226 (6.1)

733 (13.5)

354 (16.8)

Ethnicity, n (%)

    

0.039

 Russian

1,978 (94.2)

18,957 (94.4)

5,067 (93.4)

1,979 (94.2)

 Other

122 (5.8)

1,124 (5.6)

360 (6.6)

122 (5.8)

Education, n (%)

    

<0.001

 Incomp. secondary or less

81 (3.9)

448 (2.2)

119 (2.2)

47 (2.2)

 Secondary

745 (35.5)

5,700 (28.4)

1,450 (26.7)

582 (27.7)

 Vocational

624 (29.7)

6,287 (31.3)

1,998 (36.8)

769 (36.6)

 Higher

634 (30.2)

7,516 (37.4)

1,832 (33.8)

690 (32.8)

 Unknown

16 (0.8)

130 (0.6)

28 (0.5)

13 (0.6)

Marital status, n (%)

    

<0.001

 Married

1,540 (73.3)

15,334 (76.4)

4,038 (79.4)

1,706 (81.2)

 Unmarried

560 (26.7)

4,747 (23.6)

1,119 (20.6)

395 (18.8)

Residents, n (%)

    

<0.001

 Urban

1,671 (79.6)

16,160 (80.5)

4,276 (78.8)

1,587 (75.5)

 Rural

429 (20.4)

3,921 (19.5)

1,151 (21.2)

514 (24.5)

Smoking before pregnancy, n (%)

    

<0.001

 Yes

490 (23.3)

4,345 (21.6)

1,269 (23.4)

536 (25.5)

 No

1,610 (76.7)

15,736 (78.4)

4,158 (76.6)

1,565 (74.5)

Alcohol abuse during pregnancy, n (%)

0.261

 Yes

7 (0.3)

31 (0.2)

9 (0.2)

5 (0.2)

 No

2,093 (99.7)

20,050 (99.8)

5,418 (99.8)

2,096 (99.8)

Parity, n (%)

    

<0.001

 0

1,536 (73.1)

12,053 (60.0)

2,350 (43.3)

725 (34.5)

 1

501 (23.9)

7,027 (35.0)

2,540 (46.8)

1,088 (51.8)

 2+

63 (3.0)

1,001 (5.0)

537 (9.9)

288 (13.7)

 

Diabetes mellitus (types 1 or 2 or gest.), n (%)

    

0.002

 Yes

0 (0.0)

27 (0.1)

8 (0.1)

9 (0.4)

 No

2,100 (100.0)

20,054 (99.9)

5,419 (99.9)

2,092 (99.6)

Hyperemesis gravidarum, n (%)

    

<0.001

 Yes

62 (3.0)

1,223 (6.1)

631 (11.6)

377 (17.9)

 No

2,038 (97.0)

18,858 (93.9)

4,796 (88.4)

1,724 (82.1)

Preeclampsia/eclampsia, n (%)

    

0.003

 Yes

1 (<0.1)

20 (0.1)

6 (0.1)

8 (0.4)

 No

2,099 (100.0)

20,061 (99.9)

5,421 (99.9)

2,093 (99.6)

Excessive weight gain during pregnancy, n (%)

    

<0.001

 Yes

98 (4.7)

1,201 (6.0)

387 (7.1)

137 (6.5)

 No

2,002 (95.3)

18,880 (94.0)

5,040 (92.9)

1,964 (93.5)

  1. *Calculated using analysis of variances (for age as an interval variable), or chi-squared test (other variables).
  2. 25% of cells in the cross table have expected count less than 5.