Dr Nauf AlBendar, Doctor of Clinical Medicine in DOHaD & Founder of The Womb Effect, explains the role of vitamin D in pre-eclampsia in this maternal health focus
Pre-eclampsia develops due to a complex set of conditions and is characterised by increased blood pressure during pregnancy with high levels of protein in the urine.
Other symptoms include low blood platelets, abnormal liver enzymes, swelling of feet, face and hands, persistent headaches, sudden weight gain, visual disturbances and seizures.
Preeclampsia generally happens after the 20th week of gestation. However, in some cases, it occurs earlier or after delivery. The earlier preeclampsia is diagnosed and monitored, the better the outcome is for mother and baby.
According to the World Health Organization, hyper- tensive disorders of pregnancy, including gestational hypertension, pre-eclampsia and eclampsia, are among the major complications that account for approximately 14% of maternal deaths globally. Risks to the foetus include premature birth, intrauterine growth restriction and foetal death.
Despite this, the mechanism of the disease is still unclear, and the only cure, for now, is to deliver the placenta and the baby, with the potential for long-term complications.
Risk factors for pre-eclampsia
The most significant risk factors for pre-eclampsia to consider are a history of pre-eclampsia, advanced maternal and paternal age, paternal metabolic health disorders, high body mass index (BMI), chronic hypertension, pre-pregnancy diabetes mellitus (type 1 or type 2), chronic kidney disease, polycystic ovarian syndrome (PCOS), maternal periodontal disease, auto- immune disorder, assisted reproduction, and multiple pregnancies.
Nonetheless, a large body of evidence links maternal low vitamin D levels with an increased risk of preeclampsia.
Vitamin D and maternal health
Vitamin D status during pregnancy has multifaceted effects on maternal health, and the prevalence of its deficiency and insufficiency in pregnant women is concerning.
Other adverse pregnancy outcomes impacted by low maternal vitamin D levels include gestational diabetes, risk of infections, low birth weight, foetal growth restriction, caesarean section and severe postnatal haemorrhage.
Insufficient vitamin D has also been shown to have long-lasting implications in foetal outcomes, including bone mineralisation, neurocognitive development such as ADHD, autoimmunity, asthma and the increased probability of developing hypertension and heart disease in adulthood.
Preeclampsia is generally considered the late consequence of abnormal placentation and placental function, occurring in the first weeks of pregnancy.
“According to the World Health Organization, hypertensive disorders of pregnancy, including gestational hypertension, pre-eclampsia and eclampsia, are among the major complications that account for approximately 14% of maternal deaths globally. Risks to the foetus include premature birth, intrauterine growth restriction and foetal death.”
Having sufficient vitamin D levels at that time is not only crucial but is likely to play a critical role in the pathology of pre-eclamptic conditions. This could involve several biological processes such as regulating blood pressure through calcium homeostasis, acting as an anti-inflammatory agent and immune modulator, or even playing a role in epigenetic regulation by lowering the expression of placental genes related to preeclampsia.
Vitamin D is unique in that it can be both ingested through dietary intake and synthesised by the body with sun exposure.
Vitamin D status is most commonly assessed with a blood test by measuring its circulating form, 25- hydroxyvitamin D [25(OH)D], when its levels are above 50 nmol/L; it is considered adequate.
Risk factors affecting vitamin D status include season, time of the day, latitude, vegetarian diet, clothing with minimal skin exposure and skin colour. Ethnic minorities with darker skin tones tend to be at exceptionally high risk for vitamin D deficiency.
Maintaining sufficient vitamin D levels
Screening and supplementation of high-risk individuals may quickly correct vitamin D insufficiency and deficiency thus reducing the risk of preeclampsia.
Supplementation should be emphasised in the earlier weeks of pregnancy and preferably before conception to maintain sufficient vitamin D levels which is protective against hypertensive disorders.
While further work is needed to determine the optimal dose of maternal vitamin D supplementation, the most significant effects were seen among women taking a minimum of 4,000 international units per day before conception and throughout pregnancy.
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