Vitamin D How Is It Important During Pregnancy

Written by Dr. Kulyk Alexander Petrovich on Wed, 16 November 2022

Key Highlights

  • Vitamin D is a fat-soluble vitamin obtained largely from consuming fortified milk or juice, fish oils, and dietary supplements.
  • Vitamin D deficiency and insufficiency are common across the globe.
  • The relationship between low vitamin D and adverse maternal outcomes during pregnancy is crucial.
  • Scientific data proves the safety and efficacy of 4000 IU vitamin D, administered daily over 6 months of pregnancy.
  • Assessment of vitamin D status in early pregnancy or in women at preconception should be considered.

Vitamin D is a fat-soluble vitamin obtained largely from consuming fortified milk or juice, fish oils, and dietary supplements. It is also produced endogenously in the skin with exposure to sunlight.

Vitamin D for pregnant women is crucial It is a prohormone, which is known to play an important role in bone metabolism. It is also essential to promote the absorption of calcium from the gut and enables normal bone mineralization and growth.

Vitamin D during pregnancy requirements is higher, as evidenced by physiologically higher vitamin D levels seen in the second and third trimesters of pregnant women.

Decoding 'D' deficiency

Vitamin D deficiency and insufficiency are common across the globe. Studies reveal the high prevalence of vitamin D deficiency in women, including lactating mothers. The deficiency of vitamin D are well known to cause: rickets and osteomalacia (marked softening of bones) these have been linked with the condition for nearly a century now.

Various reports provide links between low vitamin D levels and various elements of the metabolic syndrome and describe the immunomodulatory, anabolic, anti-infective, and anti-tumoral potential of vitamin D.

The importance of Vitamin D during pregnancy

  • The relationship between low vitamin D and adverse maternal outcomes such as pregnancy-induced hypertension, high blood pressure in diabetic pregnancy, gestational diabetes mellitus, recurrent pregnancy loss, preterm delivery, primary Caesarian section, and postpartum depression has been documented in recent years.
  • Evidence has also accumulated regarding the impact of maternal vitamin D levels on the long-term health of offspring.
  • Studies have shown a high risk of type 1 diabetes in offspring of women with low levels of vitamin D during pregnancy. During pregnancy, severe maternal vitamin D deficiency has been associated with biochemical evidence of disordered skeletal homeostasis, congenital rickets, and fractures in the newborn.
  • New-born vitamin D levels are largely dependent on maternal vitamin D status. Consequently, infants of mothers with or at high risk of vitamin D deficiency are also at risk of vitamin D deficiency.  Vitamin D deficiency is suspected to be a public health problem in many parts of the world, especially in Asian and African countries.
  • Vitamin D deficiency in pregnancy has been associated with an increased risk of pre-eclampsia, gestational diabetes mellitus, preterm birth, small-for-gestational-age infants, impaired fetal skeletal formation causing infant rickets (softening of bones commonly leading to deformities and/or fractures) and reduced bone mass, as well as other tissue-specific conditions. Immune dysfunction, placental implantation, angiogenesis (abnormal growth of new blood vessels from pre-existing vessels), excessive inflammation, and hypertension in the mother have also been associated with vitamin D deficiency.

We have seen the importance of vitamin D for both - the mother and the baby. Now let us look at the dosage requirement that is suggested by the experts for a healthy pregnancy for the mother and the infant.

The recommended dose of Vitamin D for pregnancy

Scientific data proves the safety and efficacy of 4000 IU vitamin D, administered daily over 6 months of pregnancy. Studies have shown a significant decrease in complications of pregnancy including primary Cesarian section, hypertensive disorders of pregnancy, and comorbidities of pregnancy. While there is consensus regarding the need for vitamin D supplementation in pregnancy, there is confusion regarding optimal target levels, and the dose required to achieve them.

The optimal level of vitamin D in nonpregnant adults is defined as levels of Vitamin D which are required to maintain serum parathormone levels and prevent secondary hyperparathyroidism.

Vitamin D for pregnant women should be D >40 ng/ml, irrespective of how it is achieved. Below this level, there may be a vitamin D deficiency that may pass on to the fetus and create severe growth problems for the baby. Results of the recently conducted randomized controlled trial on vitamin D supplementation in pregnancy suggest a safe dose of 2000-4000 IU/day.

So now that we have enough data to understand how much Vitamin D is important and what would be a recommended dose for a pregnant woman, we must now try to find out about the source.

Source of Vitamin D

The only source of vitamin D is sun exposure. Therefore, to meet the increased requirements during pregnancy, vitamin D supplementation is important.

Vitamin D is a prohormone which means that it is absorbed by the skin from the sunlight and it is then metabolized to form the active form of vitamin D inside the liver.

Now, because the active form of vitamin D is not available freely, there is a higher chance of causing a vitamin D deficiency.

1. Vitamin D metabolism during pregnancy

A key role of vitamin D in the regulation of calcium homeostasis. The synthesis, metabolism, and actions of vitamin D are important for bone mineralization, immune functions, and disease prevention.

2. Vitamin D, maternal and fetal health

Maternal vitamin D nutrition in utero and breastfeeding infants is interlinked. Maternal vitamin D deficiency may expose the fetus to hypovitaminosis D and lead to vitamin D deficiency in infants at birth. Therefore, inadequate dietary intake of vitamin D during pregnancy may have a detrimental impact on maternal and fetal health.

3. Maternal and fetal bone health

During pregnancy, vitamin D plays an important role in maintaining maternal calcium homeostasis. Low vitamin D levels are associated with bone resorption and tooth loss if there is an excessive deficiency of vitamin D in the mother's body. Maternal deficiency of vitamin D is also a major factor in the development of rickets in breastfeeding infants. It is also associated with an increased risk of preterm birth.

Prenatal vitamin D and neurodevelopment

A significant association was observed between maternal vitamin D deficiency at 18 weeks gestation and language impairment at ages 5 and 10.

1. Autism Spectrum Disorder

A positive association is observed between prenatal vitamin D status with autistic traits or autism spectrum disorder (ASD). In addition to this, vitamin D deficiency was associated with a higher risk of being diagnosed with clinical ASD.

2. Risk of asthma

A high dietary vitamin D intake during pregnancy is associated with a reduced risk of wheezing in the offspring. A recent meta-analysis has reported an inverse association between prenatal intake of vitamin D and the risk of developing recurrent wheeze in the offspring.

These were the implications that would be resulted from Vitamin D deficiency. It is always advised for a pregnant mother to be adequate with the levels of Vitamin D to avoid these implications.

Vitamin D Supplementation in pregnancy and lactation and infant Growth

Is vitamin D good for pregnancy? Breastfed infants with vitamin D-sufficient mothers are protected from rickets during the first few months of life, due to the vitamin D levels which cross the placenta and lead to neonatal concentration of approximately two-thirds that of maternal vitamin D concentrations.

Moreover, the recommendation to exclusively breastfeed infants to 6 months of age has led to the introduction of vitamin D supplementation for breastfed infants. However, supplementing the lactating mother has been considered an alternative to supplementing the infant. Hence, supplementing the mother with high-dose vitamin D during lactation results in an increase in the total vitamin D concentration of breast milk thereby increasing both, the maternal and infant serum vitamin D concentrations.

Perks of Vitamin D supplementation during pregnancy

Hypovitaminosis D (vitamin D level that is below normal) in pregnancy may decrease birth weight and increase the risk of HIV mother-to-child transmission, respiratory infections, wheezing, rhinitis, eczema, type 1 diabetes, and schizophrenia in the offspring.

Severe hypovitaminosis during pregnancy may also cause fetal death, infant hypocalcemic tetany, and life-threatening cardiomyopathy. Vitamin D supplementation reduces the risk of maternal comorbidities and helps improve neonatal outcomes.

Vitamin D, through its effects on calcium absorption, parathyroid hormone (PTH) expression, phosphate metabolism, growth plate function, and possible regulation of the insulin-like growth factor axis may influence fetal and postnatal growth.

Maternal vitamin D and calcium levels are modified during pregnancy to support fetal calcium homeostasis. Clinically, neonatal hypocalcemia can result in seizures and has been associated with softening and thinning of the skull (craniotabes) and rarely, dilated cardiomyopathy.

Reduced physical activity, as well as the increase in maternal weight and fat content during pregnancy, increases the mechanical load on the skeleton and generates high levels of estrogens, which all together influence the BMD (Bone Mineral Density). A 5% loss of maternal BMD during pregnancy can occur. Lactation is also associated with hormonal fluctuations which affect the BMD.

As BMD would be affected by the weight gain and the increase in fat content, mothers need to be very careful regarding vitamin D intake to avoid any complications that can affect their, their baby's health during pregnancy and also post-delivery outcomes.

Facts about Vitamin D

  • Vitamin D deficiency during early pregnancy may lead to a lower bone mineral content (BMC) and bone mineral density (BMD) in offspring in later life and is associated with the development of rickets in infants.
  • Vitamin D deficiency during pregnancy increases the risk of preeclampsia, preterm birth, and low birth weight among
  • Vitamin D deficiency during early pregnancy impacts the neuropsychological development of children (language impairment, low quartile gross-motor development, fine motor development, attention deficit hyperactivity disorder-like symptoms, and autism-related traits) in later life.
  • Clinical evidence supports the preventive role of vitamin D during pregnancy on offspring wheeze and/or respiratory tract infections.
  • Maternal vitamin D supplementation during pregnancy of 2000 IU/d (compared with 1000 IU/d and with a placebo) results in a higher vitamin D activity of breast milk ≥2 months postpartum.
  • Prenatal to postpartum vitamin D3 supplementation is an efficacious and safe intervention in rectifying maternal and infant vitamin D deficiency.
  • Vitamin D supplementation during pregnancy reduces the risk of low-birth-weight infants and is small for gestational age, risk of preeclampsia, preterm labor, gestational diabetes, and asthma or wheezing in offspring, therefore, is beneficial.
  • Vitamin D supplementation in the lactating mother can correct the mother's vitamin D deficiency and can maintain the infants' vitamin D levels just as direct infant supplementation.
  • A dose of 4000 IU vitamin D is considered to be effective and safe and can maintain the maternal and nursing infant's vitamin D needs.
  • Pregnancy and lactation affect maternal BMD, by increasing the mechanical load on the skeleton, high levels of estrogens, and hormonal fluctuations.
  • Vitamin D along with calcium supplementation during pregnancy may have a positive effect on fetal skeletal development and can maximize fetal bone growth.
  • Treatment with vitamin D during pregnancy can help in improving the neonatal bone area, bone mineral content, and bone mineral density.
  • Higher maternal levels of Vitamin D are essential to increase intestinal calcium absorption during pregnancy and to support calcium for maternal and fetal Higher maternal levels of Vitamin D are also essential for regulating the immune system during pregnancy
  • Assessment of vitamin D status in early pregnancy or women at preconception should be considered.

Here are some of the questions that you might be facing after going through this article:

1. Will I need to take extra vitamin D in pregnancy? 

Some women are more likely to need vitamin D than others. You may have a higher risk of vitamin D deficiency if you:

  • Rarely go outside
  • Always cover your skin
  • Use high-factor sunblock
  • Have darker skin
  • Have a BMI above 30.

For anyone within these groups, taking a vitamin D supplement is especially important. But you do not need extra unless you have been diagnosed with a deficiency.

2. What foods have vitamin D? 

It is difficult to get enough vitamin D alone, but some foods help foods that help your intake.

These include:

  • Eggs
  • Oily fish (salmon and sardines, for example)
  • Red meat
  • Breakfast cereals, fat spreads, and non-dairy milk alternatives, but the amount added to these products can vary and might only be small.


Now you have enough information that is enough for you to understand the importance of vitamin d during pregnancy, its sources through diet and healthy food, and benefits of Vitamin D, and also the implication of the deficiency of Vitamin D for the health of the mother and the baby.

Follow our nutrition blogs for credible health information and have a safe and healthy pregnancy!


Dr. Kulyk Alexander Petrovich

Dr. Kulyk Alexander Petrovich is a Ukraine-based gynecologist, with extensive experience in women's health. In 1995, he graduated from the Kyiv Medical University, and specialized in gynecology. He then went on to work as a gynecologist in the Institute of Pediatric, Obstetrics and Gynecology in Kyiv, where he worked until the year 2000.

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