| | Comments |
| Perinatal risk factors |
| Maternal vitamin D deficiency | - Common in dark-skinned pregnant women, especially those with limited sun exposure (eg, living at higher latitudes, during the winter months, or routinely covering their skin)
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| Premature birth | - Premature infants have less time to accumulate vitamin D from the mother through transplacental transfer, which mostly occurs in the third trimester
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| Common postnatal risk factors |
| Exclusive breastfeeding | - Breast milk is naturally low in vitamin D, especially if the mother has vitamin D deficiency
- Supplements are needed to meet vitamin D requirements (400 international units daily)
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| Low dietary intake | - Primary dietary sources of vitamin D are fortified foods: typically beverages (milk), cereals, or infant formula
- Natural (unfortified) dietary sources of vitamin D such as oily fish, organ meats, and egg yolk are rarely consumed in sufficient quantities to meet requirements
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| Dark skin pigmentation or low sun exposure | - Cutaneous vitamin D synthesis is reduced by dark skin pigmentation, clothing, sunscreen, winter season/high latitudes, or lack of time outdoors
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| Obesity | - Vitamin D concentrations are generally lower in children with obesity because of sequestration in fat, but the clinical significance is unclear
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| Other risk factors |
| Medications | - Certain anticonvulsants, antiretroviral drugs – Enhance vitamin D catabolism
- Glucocorticoids – Inhibit vitamin D-dependent calcium absorption
- Antifungal agents (eg, ketoconazole) – Block 1-alpha-hydroxylation of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D
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| Malabsorptive conditions | - Any cause of fat malabsorption, including exocrine pancreatic insufficiency, cholestasis, extensive intestinal resection
- Liver and kidney disease may impair conversion of vitamin D to the active form (25-hydroxylation and 1-hydroxylation, respectively)
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| Genetic disorders | - Rare genetic causes of vitamin D deficiency or resistance:
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