Vitamin D in Pregnancy and Infants

If you’re pregnant or planning to be, congratulations! You’re likely researching everything you can to keep yourself and your baby healthy—including whether you’re getting enough vitamin D. This often-overlooked nutrient plays a crucial role in pregnancy, birth outcomes, and infant development.

Why Vitamin D Matters

About 20–40% of pregnant women are vitamin D deficient²—a statistic that’s concerning given its far-reaching effects. Low vitamin D in pregnancy has been linked to:

• Poor bone development and rickets in newborns³⁻⁴

• Increased risk of infection, preterm birth, and low birth weight⁵

• Higher rates of cesarean section⁶ and gestational diabetes⁷

• Developmental issues in infants, including delayed motor and social skills, respiratory infections, and even a potential reduction in autism risk when mothers supplement⁸

• Increased risk of depression during and after pregnancy (postpartum depression)⁹
  

Vitamin D influences so many systems because it acts more like a hormone than a vitamin—affecting bone health, immune function, glucose regulation, and mood.

How Vitamin D Works

Vitamin D is produced in the body when sunlight hits the skin, converting cholesterol into pre-vitamin D3. It’s then activated through the liver and kidneys. Pregnant women share this nutrient with their babies through the placenta, which has its own vitamin D receptors and enzymes¹⁰.

For both mom and baby, vitamin D supports:

• Bone and muscle development

• Immune balance to prevent infections

• Healthy glucose and insulin function (reducing gestational diabetes risk)

• Nervous system health and stable mood⁹⁻¹¹
  

Signs of Deficiency

The only reliable way to know your vitamin D status is through a blood test, but possible symptoms include:¹²

• Muscle weakness or bone pain

• Fatigue, poor wound healing, or frequent illness

• Low mood or cognitive changes

• Reduced endurance or exercise tolerance
  

Who’s at Risk for Low Vitamin D?

Even with good nutrition, certain groups are more likely to be low in vitamin D¹³⁻¹⁵:

• Vegetarians or those avoiding fortified foods

• People with limited sun exposure (especially north of San Francisco, Denver, or Richmond)

• Those with darker skin tones

• Individuals with obesity or certain chronic illnesses

• People taking anticonvulsants, glucocorticoids, antifungals, or HIV medications

• Those with absorption issues (like celiac disease)
  

If you’re pregnant and fit any of these categories, testing your vitamin D levels early and mid-pregnancy is highly recommended.¹⁶

Testing and Supplementation

Ask your provider to test your 25(OH)D level. Most experts agree that levels above 30 ng/mL support optimal bone and immune health, while levels under 32 ng/mL are considered deficient.¹⁷

Vitamin D is fat-soluble, so it can build up in the body. Supplementation should always be guided by a provider. Studies show that doses up to 4,000 IU/day are safe during pregnancy, and even 10,000 IU/day for short periods have been well-tolerated.¹³⁻¹⁴

Getting Enough Vitamin D

There are three main ways to boost levels:

1. Sun exposure – Aim for 10–15 minutes of unprotected sun 2–3 times a week (between 10 a.m.–3 p.m.).²⁰

2. Diet – Include fatty fish, egg yolks, mushrooms (UV-exposed), and fortified foods.¹⁹

3. Supplementation – Vitamin D3 is preferred for better absorption and compatibility with the body’s receptors.²¹
   

Emulsified liquid drops (often in oil) are a great option for flexible dosing and improved absorption.

Vitamin D for Infants

For babies, vitamin D is vital for bone growth and immune health. The American Academy of Pediatrics recommends:²²⁻²⁵

• Breastfed babies: 400 IU/day starting soon after birth. Alternatively, mothers taking 4,000–6,000 IU/day can pass adequate amounts through breast milk.

• Formula-fed babies: Supplementation is not needed if consuming at least 500 mL of fortified formula daily. Otherwise, add drops as advised.
  

Vitamin D plays a key role in pregnancy health, birth outcomes, and infant development. Since deficiency is common—and easily correctable—testing and guided supplementation are simple, effective ways to protect both mom and baby.

At Foundations Family Medicine in Wheat Ridge, CO, we offer comprehensive prenatal and nutritional care, including vitamin D testing and individualized supplementation plans. Together, we’ll help you feel confident and supported through every stage of pregnancy and beyond.

BOOK HERE

Dr. Jessie Miller is a Naturopathic Doctor practicing functional and holistic medicine in the Denver area with a focus on Women's health, digestion, and pediatrics. She believes that we should not settle for "common" symptoms being "normal" and that women do not have to choose between suffering and birth control or medications they don't want; there is an in between! Bridging that gap is what she does best.