The synopsis of this outcome is based on the same systematic review described under preeclampsia. Overall, the meta-analysis of 11 RCTs favored calcium supplementation RR = 0.70 (95% CI 0.57, 0.86) for the treatment of hypertension during pregnancy, with or without proteinuria. However, there was substantial between-study heterogeneity. (Included in this meta-analysis are the two large trials mentioned in the preeclampsia section, which found no significant effect of calcium supplementation on blood pressure.) The systematic review did not offer a clear explanation for the observed heterogeneity.

Based on the above, there is no clear answer to whether calcium supplementation is effective for preventing high blood pressure (with or without proteinuria) in pregnancy.

The Cochrane review that was selected for preeclampsia was applicable for hypertension during pregnancyⁱ as well.¹⁷⁶ Table 75 summarizes the findings of the Cochrane review.

A meta-analysis of 11 trials (14,946 pregnant women) suggested that calcium supplementation reduces the risk for hypertension during pregnancy (RR=0.70, 95% CI 0.57, 0.86). However, there is substantial heterogeneity among the included studies (p<0.001). As described in Table 75, the heterogeneity was not explained by whether the trials included women with low versus adequate background dietary calcium intake.

In subgroup analyses, the effects of calcium appear larger in women at high risk for hypertension versus women at low risk for hypertension. The same is observed when trials are grouped according to whether women had adequate average dietarycalcium intake versus low average calcium intake (see Table 75).

A single prospective cohort study¹⁸² (Table 68) reported no association between calcium intake levels and risk for preeclampsia.¹⁸² (See Table 69.)

• 0 – 6 mo Not applicable

• 7 mo – 2 y Not applicable

• 3 – 8 y Not applicable

• 9 – 18 y Not applicable

• 19 – 50 y Not applicable

• 51 – 70 y Not applicable

• ≥71 y Not applicable

• Postmenopause Not applicable

• Pregnant & lactating women Based on a Cochrane review that synthesized data from 11 RCTs on 14,946 pregnant women, calcium