Table 2.

Comparison of primary outcome (proportion exceeding BMI-related IOM guideline for weight gain during pregnancy) and subgroup analysis

	Intervention	Usual care	Adjusted % difference (95% CI)	Intervention–usual care
	n/N (%)	n/N (%)		Adjusted OR (95% CI)	P value
Primary analysis* Proportion exceeding IOM guideline (multiple imputation of missing 38 week weights)	81/305 (27.6)	90/311 (28.9)	−3.5 (−17.8 to 10.7)	0.84 (0.53 to 1.33)	0.46
Sensitivity analysis of proportion exceeding IOM guideline
Complete case analysis†	51/215 (23.7)	59/224 (26.3)	−4.8 (−19.8 to 10.3)	0.78 (0.48 to 1.26)	0.31
Imputation with BMI category-specific mean weight‡	85/305 (27.9)	91/311 (29.3)	−3.1 (−16.0 to 9.8)	0.86 (0.59 to 1.26)	0.44
Imputation with average weight within BMI category-related IOM threshold‡	87/305 (28.5)	93/311 (29.9)	−3.1 (−16.0 to 9.9)	0.86 (0.59 to 1.25)	0.44

Subgroup	Intervention	Usual care	Adjusted OR (95% CI)	P value (interaction)	–
BMI category at recruitment	Number exceeding IOM guideline/N (%)§	Number exceeding IOM guideline/N (%)§
Healthy weight	15/148 (10.3)	22/161 (13.5)	0.69 (0.22 to 2.21)	0.41	–
Overweight	38/95 (39.8)	34/93 (36.6)	1.11 (0.60 to 2.04)
Obese	31/62 (50.3)	34/57 (59.6)	0.69 (0.30 to 1.58)

Analysis adjusted by Site, BMI category and midwife (random effect).

*Includes objective and self-reported weights; missing weights imputed using multiple imputation; pooled estimates.

†Includes objective weights only.

‡Includes objective and self-reported weight.

§Includes objective and self-reported weights; missing weights imputed using multiple imputation; pooled estimates.

BMI, body mass index; IOM, Institute of Medicine.