The relation between maternal vitamin D and the placenta affects the development of the fetus

Vitamin D is of vital importance to the unborn child’s development of teeth, bones, immune defense, and various other things. The fetus is highly dependent on the mother’s vitamin D levels and that the nutrient can be transferred to the fetus and activated. A team of scientists has looked closer at the placenta and its role in helping the fetus utilize vitamin D. They hope their work can contribute to healthier pregnancies in the future.

Nearly all cells in the body have vitamin D receptors (VDR) that regulate different genes and a host of different biochemical processes. Vitamin D is needed for normal development of bones and teeth in the unborn child during pregnancy. Studies over the past decades have shown a link between vitamin D, heart health, immune defense, and birth weight. There are also studies that reveal an increased risk of miscarriage in vitamin D-deficient mothers, and a risk that the child is affected by neurological disorders such as ADHD. Therefore, it is of vital importance to the expecting mother to make sure her vitamin D levels are adequately high. The same goes for the vitamin D status of her unborn child.

The placenta and its important role for fetal vitamin D utilization

The new study reveals a complex interaction between vitamin D and the placenta, which underpins the importance of making sure that the pregnant women has sufficiently high vitamin D levels in her blood throughout her pregnancy. A vitamin D supplement may be necessary.
The fetus is unable to synthesize vitamin D and relies on any amount of the nutrient that it can get from the placenta. A sufficient supply of vitamin D is essential for proper fetal development and infant health right after delivery. Earlier research suggests that vitamin D is transferred passively to the fetus via the placenta, but the recent study sheds new light on the process.
In their in-vitro study, the scientists used placenta samples from women who had just given birth. They wanted to investigate how the placental cells absorb vitamin D in a process called endocytosis, and how vitamin D is metabolized afterwards. They added vitamin D in the form of 25(OH)D to the tissue samples and found that this form of the nutrient was converted into its active steroid form (1,25 (OH2DR3) by the placenta. Apparently, the activation of vitamin D in the placenta is important for placental functions and for the development of the fetus. They also observed that the plasma protein called albumin is important for cellular uptake of vitamin D, and that the CYP24A1 gene is involved in the regulation of the body’s vitamin D levels.
The placenta plays a crucial role in the uptake and activation of vitamin D. In fact, the researchers compare this process to the activation process we already know from the kidneys. This is the first study to reveal the placenta’s role in supporting the metabolism of vitamin D. The scientists only used placenta samples from completed pregnancies, but they want to make additional studies to find out more about vitamin D’s role in supporting the placenta during the early phases of pregnancy. Studies like these may contribute to healthier pregnancies. In any case, it is extremely important for pregnant women to have enough vitamin D. The new study is published in eLife, a non-profit, peer-reviewed science journal.

Widespread deficiency and official recommendation of supplements

We get very little vitamin D from our food. The main source of vitamin is sunlight during the summer period. However, there are limiting factors such as spending too much time indoors, having dark skin, being overweight, or suffering from diabetes. These factors are known to impair the body’s vitamin D synthesis. The Danish Veterinary and Food Administration recommends all adults to take 5-10 micrograms of vitamin D per day during the winter period
(October to April.) This can prevent a vitamin D deficiency prior to becoming pregnant. Furthermore, daily supplementation with 10 micrograms of vitamin D all year round is recommended for all pregnant women, dark-skinned people, and people who don’t get enough sunlight for one reason or another. Still, many pregnant women forget to take the supplement or only do it once in a while. Therefore, it may be a god idea to have your vitamin D status measured if you are pregnant – especially during the winter and spring where you are most likely to be deficient. The official recommendations for vitamin D may even be too conservative, and some people may need higher quantities than others.
EU’s Scientific Committee on Food has set 100 micrograms per day as the safe upper intake level for adults, including pregnant and breastfeeding women. This amount is equivalent to what a fair-skinned person can synthesize on a normal sunny day during the summer period.

• The Danish Health Authority advises pregnant women to take 100 micrograms of vitamin D daily
• According to science, taking vitamin D before becoming pregnant may help prevent spontaneous miscarriage
• Some people may need more vitamin D than others. A blood sample can help determine that

References:

Claire Simner et al. Placental uptake and metabolism of 25(OH) vitamin D determine its activity within the fetoplacental unit. eLife 2022

eLife. Placenta plays active part in transferring vitamin D to fetus during pregnancy. ScienceDaily march 8, 2022

Minna Sucksdorff et al. Maternal Vitamin D Levels and the Risk of Offspring Attention-Deficit/Hyperactivity Disorder. Journal of the American Academy of Child & Adolescent Psychiatry. 2019

New study sheds light on role of vitamin D in healthy pregnancy. News Medical Life Sciences June 2018

Bruce W Hollis & Carol Wagner. New Insight into vitamin D requirements during pregnancy. Bone Research 2017

New study sheds light on role of vitamin D in healthy pregnancy. News Medical Life Sciences June 2018