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What Is the Effect of Too Much Dose of Vitamin D During Pregnancy?

Vitamin D is a fat-soluble vitamin that plays an important role in bone metabolism. Vitamin D regulates calcium and phosphate levels. It is produced naturally by the body when exposed to sunlight. However, it is found in eggs and oily fish.

Vitamin D is important during pregnancy. Pregnant women should get the recommended dose of vitamin D. This vitamin is essential not only for pregnant mothers but also for their growing babies.

Why do you need Vitamin D during pregnancy?

The growing fetus depends on the maternal supply of vitamin D (25-OH Vitamin D). This form of vitamin D crosses the placenta and is transferred to the active form (1,25 (OH)2 D within the fetal kidney (Ref).

  • Several researchers reported that vitamin D is important for good immunity and for healthy bones.
  • Many studies reported a link between Vitamin D deficiency and the development of certain types of tumors and autoimmune diseases (Ref).
  • Vitamin D plays an important role in the absorption and metabolism of calcium and phosphorus.
  • According to the World Health Organization (WHO)
    • Vitamin D during pregnancy improve maternal vitamin D status
    • It could reduce the risk of pre-eclampsia
    • It decreases the risk of preterm birth and low birthweight.

What is the recommended intake of Vitamin D during pregnancy?

  • The calcium demand increases in the third-trimester pregnancy. Hence, vitamin D supplements become essential for maternal health, fetal skeletal, and optimum maternal and fetal outcomes.

The World Health Organization recommended nutrient intake (RNI) for vitamin D in pregnant women is 5 μg (200 IU) per day (Ref)

  • The Food and Nutrition Board (FNB) recommends the tolerable Upper intake level (ULs) for Vitamin D of 4,000 IU ( 100 mcg) (Ref).
    • The Upper Intake Level (UL) means the maximum daily intake unlikely to cause adverse health effects.
    • Also, the FNB recommended avoiding serum 25(OH)D levels above approximately 125–150 nmol/L (50–60 ng/mL),
  • The Institute of Medicine recommends a normal level of vitamin D of 20 ng/ml in pregnancy (Ref).

The effect of too much dose of vitamin D during pregnancy.

The harmful effect of an excessive dose of vitamin D occurs when the blood level exceeds 100 ng/ml (Ref). This could lead to the following:

  • Hypercalcemia
    • Vitamin D regulates calcium absorption. Hence, too much dose can lead to hypercalcemia.
    • It means an increased level of calcium in the blood.
    • Hypercalcemia leads to the following:
      • Nausea
      • Vomiting
      • Fatigue
      • Muscle weakness
      • Excessive urination
      • Loss of appetite
      • Dizziness.
  • Renal failure
    • This occurs due to increased levels of blood calcium. Calcification of soft tissue occurs due to accumulation of calcium in tissues.
  • A study published in 2020 reported the following:
    • The maternal high-dose of vitamin D during the third trimester didn’t improve neurodevelopment outcomes in children during their first 6 years
  • A previous study showed that:
    • Excessive intake of vitamin D during pregnancy could harm the offspring.
    • A woman who received 2,000 to 3,000 units daily dose of vitamin D her child had mental retardation, heart defects, elevated blood pressure, and kidney problems.