Pre-eclampsia (PE), which complicates ~5% of pregnancies
worldwide, is responsible for ≈46 000 maternal and >500 000 perinatal deaths
annually. Consequently, there is a need for an additional strategy to prevent
PE, especially term PE.

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