Table 1.

Birth outcomes and characteristics of mothers at baseline in relation to maternal gestational weight gain

	Alla	Optimal GWGb	Suboptimal GWGc	P valuee	Exc. GWGd	P valuef
	(n = 1,326)	(n = 517; 39%)	(n = 333; 25%)		(n = 476; 36%)
Maternal age (years)	30.2 ± 5.2	30.0 ± 5.1	30.1 ± 5.4	0.60g	30.0 ± 5.3	0.20g
Height (cm)	167.4 ± 6.0	167.3 ± 5.9	167.0 ± 6.0	0.55g	167.8 ± 6.1	0.20g
Birth weight (g)	3,721 ± 491	3,689 ± 477	3,596 ± 471	0.01g	3,844 ± 494	<0.01g
Gestational age (weeks)	39.6 ± 1.2	39.6 ± 1.1	39.4 ± 1.3	0.02g	39.8 ± 1.2	<0.01g
Prepregnancy weight (kg)	68.0 (19.0)	64.0 (16.0)	68.0 (27.0)	<0.01h	72.0 (16.0)	<0.01h
Prepregnancy BMI (kg/m2)	24.1 (6.5)	22.7 (5.1)	24.2 (9.9)	<0.01h	25.6 (5.2)	<0.01h
Prepregnancy BMI (groups)				<0.01i		<0.01i
Underweight (%)j	4	4	4		3
Normal weight (%)k	55	68	55		40
Overweight (%)l	24	15	11		43
Obese (%)m	18	13	30		14
Nulliparous (%)	39	37	35	0.52i	42	0.10i
Single (%)	6	4	6	0.15i	7	0.02i
Smoked before pregnancy (%)	16	12	11	0.76i	23	<0.01i
Smoking during pregnancy (%)	7	5	6	0.29i	9	<0.01i
Education (%)				<0.01i		<0.01i
Elementary schooling	13	10	14		15
High sch. and technical sch.	29	28	27		31
University education	35	31	39		36
Higher academic	24	30	20		19
NVP experience (%)				0.12i		0.58i
No nausea	10	10	11		9
Mild (not throwing up)	48	48	42		51
Moderate (throwing up infrequently)	33	33	33		33
Severe (throwing up daily)	10	9	14		7

Note. BMI: body mass index; Exc: excessive; GWG: gestational weight gain, NVP: nausea and/or vomiting in pregnancy.

^aValues are mean ± standard deviation or median (interquartile range) for continuous variables and percentages for categorical variables.

^bOptimal GWG was determined in accordance with the Icelandic recommendations, that is, underweight and normal‐weight women 12–18 kg total GWG and overweight and obese women 7–12 kg total GWG.

^cSuboptimal GWG was determined in accordance with the Icelandic recommendations, that is, underweight and normal‐weight women <12 kg total GWG and overweight and obese women <7 kg total GWG.

^dExcessive GWG was determined in accordance with the Icelandic recommendations, that is, underweight and normal‐weight women >18 kg total GWG and overweight and obese women >12 kg total GWG.

^eDifferences between optimal and suboptimal GWG groups.

^fDifferences between optimal and excessive GWG groups.

^g F test (Type III) of differences among groups.

^hMann–Whitney U test of differences among groups.

ⁱChi‐square test of differences among group.

^jUnderweight, BMI <18.5 kg m⁻².

^kNormal weight, BMI 18.5–24.99 kg m⁻².

^lOverweight, BMI ≥25 kg m⁻².

^mObesity, BMI ≥30 kg m⁻².