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Table 3 Associations between GWG by the IOM and adverse pregnancy outcomes overall and stratified by BMI status

From: Gestational weight gain during the second and third trimesters and adverse pregnancy outcomes, results from a prospective pregnancy cohort in urban Tanzania

End of 1st trimester BMI 2009 IOM guidelinesb Pregnancy outcomes, risk ratio (95% CI)a
   LBWc Preterm birthd SGA LGA
  Cases (n, percent)e 92, 7.5% 195, 15.9% 199, 16.2% 134, 10.9%
Total (N = 1230) Inadequate GWG (n = 517, 42.0%) 1.30 (0.67, 2.54) 0.99 (0.70, 1.40) 1.32 (0.95, 1.81) 0.54 (0.36, 0.80)
Adequate GWG
(n = 270, 22.0%)
Ref (OR = 1.00) Ref (RR = 1.00) Ref (RR = 1.00) Ref (RR = 1.00)
Excessive GWG
(n = 443, 36.0%)
1.27 (0.63, 2.53) 1.22 (0.86, 1.73) 0.96 (0.67, 1.38) 0.89 (0.62, 1.29)
  Cases (n, percent) 66, 8.7% 124, 16.4% 130, 17.2% 82, 10.8%
Normal 18.5 ≤ BMI < 25 (N = 756) Inadequate GWG (n = 343, 45.4%) 1.38 (0.63, 3.06) 1.20 (0.79, 1.84) 1.29 (0.89, 1.89) 0.65 (0.39, 1.07)
Adequate GWG
(n = 189, 25.0%)
Ref (OR = 1.00) Ref (RR = 1.00) Ref (RR = 1.00) Ref (RR = 1.00)
Excessive GWG
(n = 224, 29.6%)
1.17 (0.50, 2.72) 1.59 (1.03, 2.44) 0.96 (0.61, 1.50) 1.31 (0.83, 2.06)
  Cases (n, percent) 16, 4.0% 59, 14.7% 53, 13.2% 50, 12.4%
Overweight or obese
BMI ≥ 25 (N = 402)
Inadequate GWG
(n = 132, 32.8%)
0.54 (0.10, 2.85) 0.79 (0.40, 1.58) 1.10 (0.55, 2.18) 0.34 (0.17, 0.70)
Adequate GWG
(n = 65, 16.2%)
Ref (OR = 1.00) Ref (RR = 1.00) Ref (RR = 1.00) Ref (RR = 1.00)
Excessive GWG
(n = 205, 51.0%)
0.87 (0.21, 3.69) 0.85 (0.46, 1.57) 0.87 (0.44, 1.72) 0.45 (0.25, 0.80)
  P-heterogeneityf 0.97 0.64 0.97 0.01
  1. Institute of Medicine (IOM), gestational weight gain (GWG), body mass index (BMI), low birth weight (LBW), small for gestational age (SGA), large for gestational age (LGA), odds ratio (OR), risk ratio (RR), confidence interval (CI)
  2. aMultivariable model was adjusted for age (years), baseline gestational age (weeks), gestational age at delivery (weeks), BMI at 14 weeks of gestation (underweight, normal, overweight, obese), primigravida status (yes, no), treatment status (iron, placebo), marital status (married, other than married), education (0–4 years, 5–7 years, 8–11 years, ≥ 12 years), occupation (unemployed, unskilled or informal, skilled), and history of prior complications (yes, no)
  3. bThe IOM provided recommended ranges of weekly GWG rate during the 2nd and 3rd trimesters (kg/week) by pre-pregnancy BMI status: 0.44–0.58 kg/week for underweight, 0.35–0.50 kg/week for normal weight, 0.23—0.33 kg/week for overweight, and 0.17—0.27 kg/week for obese
  4. cModel for estimating RR did not converge due to small number of LBW events; OR from multivariable logistic regression was reported to approximate RR instead
  5. dGestational age at delivery was not adjusted in the model for preterm birth
  6. eTotal number and percent of cases in overall and in groups of normal BMI and overweight/obesity were presented
  7. fP-value for heterogeneity was computed for the interaction term between GWG and BMI status at the end of 1st trimester excluding underweight women