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Table 1 Baseline characteristics of women with twin pregnancies according to gestational weight gain

From: Examining the provisional guidelines for weight gain in twin pregnancies: a retrospective cohort study

Baseline Characteristic

All Participants

(N = 741)

Below IOM aGWG

(N = 201)

Within IOM aGWG

(N = 320)

Above IOM aGWG

(N = 220)

 
 

N (%) b

N (%) b

N (%) b

N (%) b

P value c

Maternal age, years, median (IQR)

31 (27, 34)

29 (25, 34)

32 (28, 35)

30 (26, 34)

<0.001

Caucasian

318 (82.8)

91 (82.0)

134 (84.3)

93 (81.6)

0.81

Married or common-law

556 (77.8)

145 (74.7)

255 (82.5)

156 (73.6)

0.03

Post-secondary education or higher

131 (50.4)

33 (47.1)

66 (56.4)

32 (43.8)

0.20

Neighborhood-level income quintile

    

0.36

 1st quintile

139 (19.9)

46 (23.7)

51 (17.1)

42 (20.4)

 

 2nd quintile

109 (15.6)

33 (17.0)

46 (15.4)

30 (14.6)

 

 3rd quintile

143 (20.5)

38 (19.6)

57 (19.1)

48 (23.3)

 

 4th quintile

161 (23.0)

45 (23.2)

70 (23.4)

46 (22.3)

 

 5th quintile

147 (21.0)

32 (16.5)

75 (25.1)

40 (19.4)

 

Pre-pregnancy BMI, kg/m2, median (IQR)

25.5 (22.5, 30.3)

26.0 (22.6, 32.7)

25.0 (22.1, 29.5)

25.7 (23.0, 30.1)

0.07

Pre-pregnancy BMI classification

    

0.15

 Normal weight (BMI 18.5 to 24.9 kg/m2)

350 (47.2)

93 (46.3)

161 (50.3)

96 (43.6)

 

 Overweight (BMI 25.0 to 29.9 kg/m2)

196 (26.5)

45 (22.4)

84 (26.3)

67 (30.5)

 

 Obese (BMI ≥ 30.0 kg/m2)

195(26.3)

63 (31.3)

75 (23.4)

57 (25.9)

 

Parity ≥1

390 (52.6)

119 (59.2)

172 (53.8)

99 (45.0)

0.01

Previous gestational diabetes d

15 (2.0)

NA

NA

NA

0.76

Previous gestational hypertension

29 (3.9)

8 (4.0)

14 (4.4)

7 (3.2)

0.78

Previous Caesarean section

86 (11.7)

20 (10.1)

40 (12.6)

26 (12.0)

0.68

Previous LBW d

20 (2.8)

NA

NA

NA

0.31

Previous neonatal death

7 (1.0)

NA

NA

NA

0.31

Smoking during pregnancy

68 (10.3)

30 (17.2)

23 (7.8)

15 (7.9)

0.002

Drug use during pregnancy d

15 (2.0)

NA

NA

NA

0.64

Pre-existing diabetes mellitus d

9 (1.2)

NA

NA

NA

0.002

Pre-existing hypertension d

15 (2.0)

NA

NA

NA

0.32

Other physical health problems

194 (26.2)

57 (28.4)

84 (26.3)

53 (24.1)

0.61

Mental health problems

69 (9.3)

17 (8.5)

29 (9.1)

23 (10.5)

0.76

Attended prenatal classes

143 (41.9)

42 (43.3)

50 (35.2)

51 (50.0)

0.07

Twin type

    

0.52

 Monochorionic – diamniotic

144 (19.4)

42 (20.9)

52 (16.3)

50 (22.7)

 

 Dichorionic (dissimilar sexes or blood groups)

294 (39.7)

77 (38.3)

128 (40.0)

89 (40.5)

 

 Dichorionic (similar sexes and blood groups)

135 (18.2)

34 (16.9)

64 (20.0)

37 (16.8)

 

 Dichorionic (similar sexes but blood groups undetermined)

168 (22.7)

48 (23.9)

76 (23.7)

44 (20.0)

 

Sex of the baby e

    

0.40

 Male

699 (47.2)

203 (50.5)

294 (45.9)

202 (46.0)

 

 Female

782 (52.8)

199 (49.5)

346 (54.1)

237 (54.0)

 
  1. Abbreviations: BMI, body mass index; GWG, gestational weight gain; IOM, Institute of Medicine; IQR, inter-quartile range; N, number; NA, not available
  2. a GWG categories (below, within, and above IOM GWG) are based on the 2nd and 3rd trimester weekly rates of GWG
  3. b Baseline characteristics are mostly reported as N (%), unless otherwise specified (i.e., median (IQR))
  4. c P values were calculated with the Kruskal-Wallis test for continuous variables and with the χ2 test or Fisher’s exact test for categorical variables
  5. d The proportions of previous gestational diabetes, previous LBW, previous neonatal death, drug use during pregnancy, pre-existing diabetes mellitus, and pre-existing hypertension could not be reported by GWG category in order to preserve the confidentiality of the research subjects, since some cells had <5 events
  6. e Sex of the baby is reported at the neonatal level and not the maternal level, thus total N = 1482; the sex of one baby was ambiguous; the p-value is based on the analysis of generalized estimating equations parameter estimates