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Table 1 Population Characteristics of Study I (2010–2012) and Study II (2010–2013), Dar es Salaam, Tanzania

From: Methodological approaches to imputing early-pregnancy weight based on weight measures collected during pregnancy

Characteristic Study I Entire set (N=1472) Study I Testing set (N=200) p-valuea Study II Entire set
(N=2131)
Study II Testing set
(N=200)
p-valuea
Age at baseline (years), mean (SD) 23.9 (4.1) 23.7 (4.0) 0.52 22.6 (3.9) 22.7 (3.8) 0.98
Weight at baseline (kg), mean (SD) 59.7 (11.7) 58.6 (11.7) 0.14 55.6 (11.0) 55.1 (10.1) 0.57
Height at baseline (cm), mean (SD) 156.1 (6.1) 157.1 (6.4) 0.07 154 .7 (6.1) 154.8 (6.1) 0.90
Gestational week at baseline (weeks), mean (SD) 17.8 (4.4) 12.7 (2.1) < 0.0001 10.0 (2.4) 9.8 (2.4) 0.22
Total number of antenatal visits, range (median) 1–9 (5) 2–9 (6) < 0.0001 1–10 (6) 3–10 (7) < 0.0001
Weight at the end of 1st trimester (kg), mean (SD)b   58.7 (11.6)    55.3 (9.9)  
Last available weight measure at the end of 2nd trimester (kg), mean (SD) 62.2 (11.7) 62.7 (11.5) 0.58 59.8 (10.7) 59.6 (9.6) 0.82
BMI based on last available weight at the end of 2nd trimester (kg/m2), mean (SD) 25.5 (4.6) 25.4 (4.7) 0.70 25.0 (4.2) 24.9 (3.8) 0.68
Gestational age at delivery (weeks), mean (SD) 39.5 (3.5) 39.0 (3.2) 0.07 38.8 (2.7) 39.1 (2.4) 0.084
Treatment status (control), n (%)c 738 (50.1) 102 (51.0) 0.79 533 (25.0) 41 (20.5) 0.19
Primigravida, n (%) 613 (41.6) 91 (45.5) 0.23 1024 (48.1) 104 (52.0) 0.25
Marital Status, n (%)    0.36    0.15
 Married or co-habiting 1172 (79.6) 164 (82.0)   1908 (89.5) 185 (92.5)  
 Other/missing 300 (20.4)d 36 (18.0)   223 (10.5) 15 (7.5)  
BMI at baseline (kg/m2), n (%)    0.04    0.74
 Underweight (< 18.5) 68 (4.6) 16 (8.0)   244 (11.5) 19 (9.5)  
 Normal (18.5–25) 840 (57.1) 119 (59.5)   1297 (60.9) 128 (64.0)  
 Overweight (25–30) 396 (26.9) 41 (20.5)   420 (19.7) 37 (18.5)  
 Obese (≥30) 168 (11.4) 24 (12.0)   169 (7.9) 16 (8.0)  
Education status, n (%)    0.34    0.38
 0–4 years 32 (2.2) 5 (2.5)   177 (8.3) 12 (6.0)  
 5–7 years 781 (53.1) 104 (52)   1345 (63.2) 133 (66.5)  
 8–11 years 406 (27.6) 57 (28.5)   498 (23.4) 42 (21.0)  
 ≥12 years 214 (14.5) 32 (16.0)   110 (5.2) 13 (6.5)  
Unknown 39 (2.7) 2 (1.0)   1 (0.05) 0 (0.0)  
Occupation status, n (%)    0.69    0.12
 Unemployed 700 (47.6) 98 (49.0)   1174 (55.1) 110 (55.0)  
 Unskilled or informal 445 (30.2) 63 (31.5)   514 (24.1) 51 (25.5)  
 Skilled 280 (19.0) 34 (17.0)   113 (5.3) 4 (2.0)  
 Other/unknown 47 (3.2) 5 (2.5)   330 (15.5) 35 (17.5)  
Non-live birth in previous pregnancy, n (%)e 126 (20.6) 27 (29.7) 0.02 219 (20.7) 15 (16.7) 0.32
Prior history of complications, n (%)f 109 (7.4) 18 (9.0) 0.35 115 (5.4) 7 (3.5) 0.21
  1. Abbreviations: BMI body mass index
  2. aP-value from chi-square test comparing categorical covariate and analysis of variance comparing continuous covariate between testing set and the rest of entire set was presented
  3. bAmong participants with available weight measures taken at end of trimester 1 during 12–14 weeks of gestation who were included in the testing sets
  4. cTreatment was 60 mg iron supplement for Study I; Zinc and Vitamin A (as a 2-by-2 factorial design) for Study II (vitamin A only, zinc only, vitamin A and zinc, placebo). N (%) of the control group was presented for each study
  5. dOne person had missing marital status in Study I
  6. eNon-live birth included fetal death, abortion, miscarriage, ectopic pregnancy among non-primigravida women
  7. fPrior history of complication included any history of the following: CVD, high blood pressure, diabetes, weight loss in previous year, or ever having a low birth weight baby if non-primigravida