These were the results of a study conducted by researchers at Maastricht University and Maastricht UMC+. Their calculation model included data from medical literature, population statistics, expert opinions and their own research study. The researchers will present their findings on 22 January during a conference organised by Kennispoort Verloskunde (the Dutch obstetrics knowledge portal) in Utrecht.

Preeclampsia is a pregnancy complication that can be life-threatening for both mother and child and has been linked to developmental delays and premature birth. One in thirty pregnant women develop preeclampsia, with roughly 5,000 women being diagnosed in the Netherlands each year. 

Randomised studies have shown that women who start taking calcium supplements in their second trimester and continue until the end of their pregnancies can reduce their risk of developing preeclampsia by 55%. This can also reduce the risk of premature birth by 24%. The positive impact of calcium supplementation is greatest in women with low calcium levels and women with an increased risk for developing preeclampsia.

Less than 5% of pregnant women currently take calcium supplements. If 100% of pregnant women were to take supplements, this rate could be reduced by more than half. In their calculation model, the Maastricht researchers assumed that not all pregnant women would follow their advice. Since the nineties, pregnant women have been advised to take folic acid supplements before conception to reduce the risk of spina bifida in their unborn children. Roughly half of all pregnant women follow this recommendation.

The Dutch Health Council recommends that all pregnant women consume at least 1 gram of calcium per day, but an estimated one in three women fail to do so. Dairy products, nuts and vegetables are all high in calcium. Individuals who consume very few dairy products are more likely to have a calcium deficiency. In the aforementioned study, a proven effect was found in supplements that contain 1 to 2 grams of calcium. However, most multivitamin supplements for pregnant women contain only a fraction of this recommended amount. Pregnant women interested in taking calcium supplements are advised to consult with their obstetrician or gynaecologist before starting.

The Maastricht calculation model was made possible thanks to a grant from the Fonds Gezond Geboren foundation. The study was led by epidemiologist Luc Smits (UM) and gynaecologist Liesbeth Scheepers (MUMC+).