Understanding Vitamin D and Bone Health in Preterm Infants: A Parent’s Guide

Our bones are essential not only for structure but also as reservoirs for vital minerals like calcium, phosphorus, and magnesium. These minerals help maintain a healthy balance in the body, and vitamin D plays a key role by enhancing the absorption of calcium from the diet. For preterm infants—especially those born before 30 weeks—this balance can be more challenging to achieve.

Why Preterm Infants Are at Risk

During the third trimester, a fetus receives a rapid transfer of calcium and phosphorus from the mother, which is crucial for strong bone development. When babies are born early, they miss out on much of this natural buildup. In addition:

• Limited Physical Activity: Fetal movement in the third trimester helps stimulate bone growth. Preterm infants often have reduced activity, which can impact bone strength.

• Increased Mineral Loss: Premature babies tend to excrete more phosphorus and may be affected by medications (such as diuretics or steroids) that lower calcium levels.

• Subtle Symptoms: Osteopenia, or low bone mineral density, often shows few symptoms until bones become weak and more prone to fractures.

How Bone Health Is Monitored and Supported

Healthcare providers use several methods to monitor bone health in preterm infants:

• Blood Tests: These check levels of calcium, phosphorus, and alkaline phosphatase to gauge mineral status.

• Imaging Techniques: Ultrasound and radiography can detect changes in bone density and early signs of rickets.

Since the natural mineral content of human milk may not fully meet the needs of a growing preterm infant, many are given supplementary calcium and phosphorus. This is often achieved through fortified human milk or specially designed preterm formulas.

The Role of Vitamin D

Vitamin D is crucial for helping the body absorb calcium properly. It must first be converted by the liver and kidneys into its active form to work effectively. For infants who have reached a weight of more than 1500 grams and can tolerate full enteral feeds, a daily intake of approximately 400 IU to 1000 IU of vitamin D is generally recommended. While vitamin D deficiency is common, especially in those with darker skin or obesity, routine screening isn’t universally recommended. Pediatricians typically monitor levels closely and treat deficiencies as needed.

What This Means for Parents

If your baby was born preterm, staying on top of their nutritional needs is essential to help them build strong bones and avoid complications such as osteopenia or rickets. Regular check-ups that include blood tests and, when necessary, imaging studies, help ensure that any issues are caught early. Working with your healthcare provider, you might be advised to use fortified milk or special formulas, along with appropriate vitamin D supplementation, to support optimal bone development.

By understanding these basics, you can better navigate the nutritional and developmental needs of your preterm infant and help set the stage for a healthy future. Always consult with your pediatrician to determine the best plan for your child’s specific needs.