(a) Primary outcome. Increase from gestational week 12 to labour in diastolic (DBP) and systolic (SBP) blood pressure

Variable	Magnesium (n = 83)	Placebo (n = 93)	p value
Increase in DBP ≥15 or SBP ≥30 mm Hg
0 (no)	46 (56.1%)	56 (60.2%)
1 (yes)	36 (43.9%)	37 (39.8%)	0.69
Increase in DBP of ≥15 mm Hg (maximum increase)
0 (no)	47 (57.3%)	57 (61.3%)
1 (yes)	35 (42.7%)	36 (38.7%)	0.70
Maximum increase in DBP	12.4 (8.3)	10.6 (9.4)	0.17
	10.0 (-5.0; 35.0)	10.0 (-10.0; 30.0)
	n = 83	n = 93
Increase in SBP of ≥30 mm Hg (maximum increase)
0 (no)	77 (93.9%)	84 (90.3%)
1 (yes)	5 (6.1%)	9 (9.7%)	0.56
Maximum increase in SBP	12.6 (10.7)	12.9 (11.7)	0.96
	10.0 (-10.0; 55.0)	10.0 (-5.0; 60.0)
	n = 83	n = 93
Gestational HT
0 (no)	62 (75.6%)	78 (83.9%)
1 (yes)	20 (24.4%)	15 (16.1%)	0.24

For categorical variables, n (%) is presented.

For continuous variables, mean (SD)/median (min; max)/n is presented.

For comparison between groups, Fisher's exact test (lowest 1-sided p value multiplied by 2) was used for dichotomous variables and the Mann–Whitney U test was used for continuous variables.