The effect of calcium supplementation on blood pressure in non-pregnant women with previous pre-eclampsia: An exploratory, randomized placebo controlled study

• An overall effect of calcium supplementation on blood pressure was not confirmed.
• We found a non-statistically significant trend to reduced blood pressure.
• The trend was statistically significant in the higher-risk group diastolic pressure.
• Results are consistent with possible role for calcium in pre-eclampsia aetiology.
• Diastolic pressure may be more sensitive to calcium in previous severe preeclampsia.

BackgroundEpidemiological findings suggest that the link between poverty and pre-eclampsia might be dietary calcium deficiency. Calcium supplementation has been associated with a modest reduction in pre-eclampsia, and also in blood pressure (BP).MethodsThis exploratory sub-study of the WHO Calcium and Pre-eclampsia (CAP) trial aims to determine the effect of 500 mg/day elemental calcium on the blood pressure of non-pregnant women with previous pre-eclampsia. Non-pregnant women with at least one subsequent follow-up trial visit at approximately 12 or 24 weeks after randomization were included.ResultsOf 836 women randomized by 9 September 2014, 1st visit data were available in 367 women of whom 217 had previously had severe pre-eclampsia, 2nd visit data were available in 201 women. There was an overall trend to reduced BP in the calcium supplementation group (1–2.5 mmHg) although differences were small and not statistically significant. In the subgroup with previous severe pre-eclampsia, the mean diastolic BP change in the calcium group (−2.6 mmHg) was statistically larger than in the placebo group (+0.8 mmHg), (mean difference −3.4, 95% CI −0.4 to −6.4; p = 0.025). The effect of calcium on diastolic BP at 12 weeks was greater than in those with non-severe pre-eclampsia (p = 0.020, ANOVA analysis).ConclusionsThere is an overall trend to reduced BP but only statistically significant in the diastolic BP of women with previous severe pre-eclampsia. This is consistent with our hypothesis that this group is more sensitive to calcium supplementation, however results need to be interpreted with caution.