TABLE 8. Population characteristics by treatment group in the study of the effect of calcium supplementation on preterm deliveries.

Characteristic	Calcium (N = 95)	Placebo (N = 95)	p Value
Maternal age (yr) (mean + SD)	16.2 + 0.8	16.3 + 0.9	NS
Education (yr) (mean SD)	9.3 + 1.3	9.4 + 1.5	NS
Maternal height (in) (mean + SD)	64.6 + 10.0	65.8 + 14.9	NS
Black race	92.6	94.7	NS
Marital status (single %)	97.9	98.9	NS
Previous preterm delivery (<37 wk) (%)	2.1	2.1	NS
Previous low birth weight (<2500 gm) (%)	2.1	2.1	NS
Previous pregnancy-induced hypertension (%)	2.1	2.1	NS
Spontaneous abortions (%)	5.3	8.4	NS
Induced abortions (%)	15.2	18.9	NS
Primigravid (%)	70.5	61.0	NS
Nulliparous (%)	88.4	98.9	NS
Gestational age (wk)	23.7 + 4.3	23.4 + 3.8	NS
Uterine height (cm)	23.7 + 4.1	23.6 + 3.8	NS
Maternal weight (kg)	63.0 + 10.6	67.4 + 13.5	p<0.01
Systolic blood pressure (mm Hg)	103.1 + 9.2	102.4 + 10.4	NS
Diastolic blood pressure (mm Hg)	60.9 + 8.8	61.3 + 8.0	NS

Values are mean + SD. Calcium supplementation of 2.0 gm/day of elemental calcium.

Source: Villar (23).