While many pregnancies go smoothly, problems can come up. One of those problems is a sharp rise in blood pressure, resulting in hypertension. Hypertension-related complications of pregnancy impact roughly 5-8% of all pregnancies. This risk is 1.5-2 times higher for first pregnancies. Hypertension in pregnancy can be quite dangerous—it’s responsible for 14% of all pregnancy-related deaths. Among hypertension-related complications, pre-eclampsia makes up roughly half of these.
Pre-eclampsia is clinically defined as elevated blood pressure (140/90 mmHg over two occasions, or 160/110 on one occasion) in women who aren’t normally hypertensive, occurring after 20 weeks of pregnancy, accompanied by protein in the urine, liver or kidney problems, fluid in the lungs, or low platelet count.
The causes and effects of pre-eclampsia are laid out in Figure 1. Reductions in pre-eclampsia may reduce the overall risk of maternal deaths.
Previous epidemiological data point toward calcium being a potential mitigator of pre-eclampsia risk. For example, pre-eclampsia rates have been observed to be much lower in populations of people who have high calcium diets. Previously, a randomized trial found that 1500 milligrams of calcium supplementation 20 weeks into pregnancy through full term did not reduce the risk of pre-eclampsia, but did reduce its severity. Additionally, a meta-analysis in the Cochrane database found a large reduction (-55%) in the risk of pre-eclampsia due to calcium supplementation. However, the results may have been largely influenced by publication bias with only potentially under-powered small-scale studies reporting significant benefits. This suggests that the underlying literature base may be unreliable. Furthermore, there have been no trials that look at pre-pregnancy and early pregnancy calcium supplementation on the risk of pre-eclampsia to date.
The present study was designed to overcome these problems. It is a larger, longer term parallel arm, double-blind, randomised, placebo-controlled trial testing the effect of calcium supplementation given before and during early pregnancy on pre-eclampsia.
Higher calcium intake has been associated with a reduced risk of pre-eclampsia, which is responsible for almost half of all hypertension-related pregnancy complications. Randomized controlled trials and meta-analysis have shown inconsistent results with calcium supplementation on the risk of pre-eclampsia. The present study was a parallel arm, double-blind, randomised, placebo-controlled trial testing the effect of calcium supplementation given before and during early pregnancy on pre-eclampsia.