Does Antenatal Vitamin D Supplementation Influence Bone's Postnatal Response to Mechanical Stimulation?

Fractures in children are common and the incidence is increasing. They are more common in children who have small, narrow and weak bones. Studies have shown that fractures in early childhood are associated with later bone strength.

There are several (i) non-modifiable (age, gender, race, genetics) and (ii) modifiable factors such as nutrition (vitamin D & calcium intake) and exercise that can contribute to bone strength.

Low calcium is associated with an increased risk of fracture. Vitamin D plays a pivotal role in bone health by increasing the absorption of calcium from the gut. Investigators know from the previous research that there is a reduction in bone strength in children whose mothers had lower vitamin D levels during pregnancy.

Bone growth can also be achieved by loading of bone during childhood in the form of regular sport activities such as gymnastics and exercise programmes. Equally it can be achieved by using whole body vibration (WBV). WBV is the application of vibratory stimulus to the body in a synchronous fashion by which the bones are made much stronger reducing the risk of fracture in later life. Thus WBV can be used as a means to assess bone responsiveness to mechanical stimulation. Studies have shown that standing on a vibrating platform for 10 minutes a day can significantly increase the bone mass. Investigators' own research has also shown that healthy boys when made to stand on a vibration platform for 10 minutes daily for 5 days increased the strength and quality of their bones.

Thus the role of diet and mechanical loading are of considerable interest in determining their role in bone health and the prevention of fractures.

Maternal Vitamin D Osteoporosis Study (MAVIDOS) is a large study conducted recently at 3 different big centres (Sheffield, Southampton and Oxford). Results from this study have shown that giving a higher dose of vitamin D to pregnant women every day from 14 weeks of pregnancy increased the strength of the bones in their infants. In the proposed study Investigators aim to show how vitamin D supplementation during pregnancy affects the response of bone to vibration in children whose mothers participated in the MAVIDOS study in Sheffield. These children will be 4 years of age when they participate in this study.

The results of this study will help inform public health policy on vitamin D intake during pregnancy. This will also help the investigators identify a possible risk factor for poor bone health in children.