TABLE 1.

Age-standardized baseline characteristics according to quartiles of total iron intake in women with a history of GDM¹

	Quartile of total iron intake
Characteristic	1	2	3	4	P-difference
Participants, n	982	1005	995	994	—
Age, y	37.5 ± 4.62	37.7 ± 4.6	37.9 ± 4.5	37.6 ± 4.7	0.22
Family history of diabetes, %	29.0	27.2	26.8	22.6	0.01
Race, Caucasian, %	92.5	91.1	92.0	91.7	0.66
Current oral contraceptive use, %	8.4	9.1	9.2	8.5	0.97
Current smoking, %	14.4	12.5	9.1	7.4	<0.001
Alcohol, g/d	2.7 ± 6.0	2.2 ± 4.5	2.2 ± 4.3	2.1 ± 4.3	0.02
BMI, kg/m2
At baseline	27.1 ± 6.7	27.4 ± 6.6	26.7 ± 6.1	26.1 ± 5.9	<0.001
At age 18 y	21.2 ± 3.4	21.8 ± 3.7	21.4 ± 3.2	21.1 ± 3.2	<0.001
Physical activity, MET-h/wk	16.1 ± 23.6	17.2 ± 24.4	16.9 ± 19.9	18.4 ± 23.2	<0.001
Total calories, kcal/d	1847 ± 585	1928 ± 579	1995 ± 568	1851 ± 540	<0.001
Carbohydrates, energy, %	47.7 ± 7.5	48.7 ± 7.2	50.9 ± 7.2	50.4 ± 7.8	<0.001
Total protein, energy, %	18.6 ± 3.5	19.9 ± 3.4	19.5 ± 3.2	19.8 ± 3.6	<0.001
Total fat, energy, %	34.2 ± 5.7	32.3 ± 5.6	30.9 ± 5.7	30.9 ± 5.9	<0.001
SFAs, energy, %	12.4 ± 2.4	11.2 ± 2.3	10.7 ± 2.4	10.9 ± 2.5	<0.001
MUFAs, energy, %	13.1 ± 2.5	12.4 ± 2.6	11.8 ± 2.6	11.8 ± 2.6	<0.001
PUFAs, energy, %	5.8 ± 1.6	5.7 ± 1.4	5.6 ± 1.3	5.4 ± 1.5	<0.001
trans Fat, energy, %	1.9 ± 0.7	1.7 ± 0.6	1.6 ± 0.6	1.5 ± 0.6	<0.001
Dietary cholesterol,3 mg/d	250.1 ± 64.0	256.6 ± 73.0	240.5 ± 71.8	244.5 ± 75.8	<0.001
Total fiber,3 g/d	15.6 ± 4.0	18.5 ± 4.7	19.9 ± 5.7	19.3 ± 5.6	<0.001
Cereal fiber,3 g/d	4.3 ± 1.8	5.5 ± 2.1	6.5 ± 2.8	6.3 ± 3.2	<0.001
Fruit fiber,3 g/d	2.9 ± 2.2	3.2 ± 2.1	3.5 ± 2.2	3.6 ± 2.2	<0.001
Vegetable fiber,3 g/d	5.5 ± 2.4	7.1 ± 3.1	7.3 ± 3.7	6.8 ± 3.4	<0.001
Glycemic index3	53.7 ± 3.5	54.0 ± 3.2	53.9 ± 3.4	53.4 ± 3.6	<0.001
Glycemic load3	115.7 ± 21.8	118.4 ± 20.3	123.3 ± 21.1	121.6 ± 22.5	<0.001
Zinc,3 mg/d	11.6 ± 4.8	13.0 ± 7.4	16.1 ± 9.5	25.6 ± 16.3	<0.001
Calcium,3 mg/d	941.7 ± 409.7	935.0 ± 399.6	1042.3 ± 398.1	1256.5 ± 500.3	<0.001
Magnesium,3 mg/d	271.5 ± 53.2	302.6 ± 58.8	338.0 ± 68.5	363.9 ± 92.7	<0.001
Potassium,3 mg/d	2760.8 ± 536.0	2976.2 ± 512.1	3078.3 ± 578.8	3096.3 ± 583.0	<0.001
Vitamin E,3 mg/d	17.7 ± 51.0	21.9 ± 54.7	24.8 ± 46.5	44.0 ± 86.4	<0.001
Vitamin C,3 mg/d	167.1 ± 193.1	207.4 ± 252.2	248.8 ± 276.1	340.3 ± 383.4	<0.001
Folate,3 μg/d	316.2 ± 163.2	361.3 ± 163.5	461.8 ± 163.3	749.4 ± 350.5	<0.001
Caffeine,3 mg/d	221.7 ± 204.9	233.4 ± 214.8	208.4 ± 194.8	199.0 ± 201.5	<0.001
Red meat, servings/d	1.1 ± 0.6	1.1 ± 0.7	1.0 ± 0.7	0.9 ± 0.6	<0.001
Poultry, servings/d	0.4 ± 0.3	0.5 ± 0.3	0.5 ± 0.3	0.5 ± 0.3	<0.001
Fish, servings/d	0.2 ± 0.2	0.2 ± 0.2	0.3 ± 0.2	0.2 ± 0.2	<0.001
Eggs, servings/d	0.2 ± 0.2	0.2 ± 0.3	0.2 ± 0.2	0.2 ± 0.2	0.34
Fruit, servings/d	1.0 ± 0.9	1.2 ± 0.9	1.4 ± 1.1	1.3 ± 0.9	<0.001
Vegetables, servings/d	2.8 ± 1.5	3.8 ± 2.1	4.1 ± 2.5	3.5 ± 2.1	<0.001
Nuts, servings/d	0.3 ± 0.4	0.3 ± 0.4	0.3 ± 0.3	0.3 ± 0.4	0.36
Legumes, servings/d	0.3 ± 0.3	0.4 ± 0.3	0.5 ± 0.4	0.4 ± 0.4	<0.001
Whole grains, servings/d	0.8 ± 0.8	1.1 ± 1.0	1.3 ± 1.1	1.2 ± 1.1	<0.001
Sugar-sweetened beverages, servings/d	0.7 ± 1.1	0.4 ± 0.8	0.4 ± 0.8	0.4 ± 0.8	<0.001

¹Baseline was defined as 1991 for prevalent GDM, and the year of the index pregnancy was used for incident GDM. All comparisons across quartiles of total iron intake were significant except for the following: age, race-ethnicity, current oral contraceptive use, and the consumption of eggs and nuts. GDM, gestational diabetes mellitus; MET-h, metabolic equivalent task hours.

²Mean ± SD (all such values).

³All values were energy adjusted.