Low Maternal Calcium Intake not independent contributor to development of Pre-Eclampsia Risk: Study

Meta-analyses of several randomised trials have reported that Ca supplementation reduces the risk of PE by more than 50%, especially in countries with low Ca intake. As such, the World Health Organization recommends 1.5-2 g elemental Ca daily from 20weeks' gestation, for pregnant women with low dietary Ca intake.

In this cohort study of women undergoing routine assessment at 35+0–36+6 weeks' gestation, in an ethnically and socioeconomically diverse population in London, UK, authors sought to understand the interrelationships between dietary Ca intake and PE incidence.

This was a prospective observational cohort study of women with singleton pregnancies who attended the Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London UK, for a routine clinical assessment at 35+0–36+6 weeks' gestation.

A total of 2838 women with singleton pregnancies were studied at 35+0–36+6 weeks' gestation, including 96 (3.4%) who subsequently developed PE. Online 24-h dietary recall questionnaire was used to measure Ca intake. In the low (<700mg/d) vs. adequate (≥700mg/d) Ca intake groups, authors compared the prevalence of PE-associated maternal risk factors and the incidence of PE. In multivariate regression, they examined the low Ca intake and PE relationship, adjusted for established PE risk factors (including blood pressure and angiogenic biomarkers) and any additional factors associated with low Ca intake specifically.

Overall, 405 (14.3%) women had low Ca intake. Low (vs. adequate) Ca intake was associated with a higher incidence of PE (6.2% vs. 2.9%; odds ratio 2.2, 95% confidence interval 1.3–3.7), as well as more prevalent risk factors for PE, including Black ethnicity (34.1% vs. 11.8%), South Asian ethnicity (10.1% vs. 7.2%), high body mass index (29.8 vs. 28.3kg/m2 ) and more deprived index of multiple deprivation (54.3% vs. 35.5%). In multivariate regression adjusting for other PE risk factors, low Ca intake was no longer associated with PE (OR 1.7, 95% CI 0.9–3.2).

In a cohort of ~3000 unselected women from an area of urban London characterised by ethnic diversity and deprivation representative of the UK, authors observed that low Ca intake (<700mg/ day) was common (44%), although less so (14%) when the high calcium content of water in South London was taken into account. Low Ca intake was associated with many established risk factors for PE, including ethnicity and social deprivation. Although low Ca intake that accounted for the Ca content of water was associated with a doubling in the odds of PE, the association diminished and was no longer significant when other PE risk factors were accounted for in multivariate regression or if Ca intake was assessed among women who provided only one/two Intake24 recalls. Although they cannot rule out some causal effect of low Ca on incidence of PE, study cannot conclude that there is an independent association between low Ca and incidence of PE.

Low Ca intake that takes into account the calcium content of water, is associated with an increased risk of PE, as well as other established PE risk factors. When these are taken into account, there is no evidence that low Ca intake makes an independent contribution to development of PE in a population of mixed ethnicity women. However, there is uncertainty about the effect of calcium. One explanation for why authors cannot rule out some effect could be that in our models, they do not fully capture risk factors such as deprivation and that calcium acts as a proxy for this. Whether or not low Ca intake may mediate at least some of the relationship between established risk factors (e.g., deprivation) and PE risk remains to be determined, by work that better defines baseline maternal characteristics, baseline Ca intake and PE risk.

Source: Anastasija Arechvo1,2 | Argyro Syngelaki1,2 | Laura A. Magee2; BJOG: An International Journal of Obstetrics & Gynaecology, 2025; 0:1–10 https://doi.org/10.1111/1471-0528.18091