Reduced tibial speed of sound in Chinese infants at birth compared with Caucasian peers: the effects of race, gender, and vitamin D on fetal bone development

Early Life Programming of Skeletal Health

PURPOSE OF REVIEW

Increasing bone mineral accrual during childhood might delay the onset of osteoporosis. We discuss the scientific evidence for early life approaches to optimising skeletal health.

RECENT FINDINGS

There is an ever-growing body of evidence from observational studies suggesting associations between early life exposures, particularly during foetal development, and bone mineral density (BMD). The findings of such studies are often heterogeneous, and for some exposures, for example, maternal smoking and alcohol intake in pregnancy or age at conception, intervention studies are not feasible. The most frequently studied exposures in intervention studies are calcium or vitamin D supplementation in pregnancy, which overall suggest positive effects on offspring childhood BMD. Maternal calcium and/or vitamin D supplementation during pregnancy appear to have positive effects on offspring BMD during early childhood, but further long-term follow-up is required to demonstrate persistence of the effect into later life.

Vitamin D Levels in Pregnant Women Do Not Affect Neonatal Bone Strength

Vitamin D plays a key role in regulating calcium and phosphate metabolism. However, whether maternal vitamin D levels affect fetal bone strength is unclear. This study assessed correlations between maternal 25(OH)D status and neonatal bone strength 25(OH)D levels, these were measured in the maternal and infant cord blood of 81 mother−infant dyads. Bone strength was measured using a quantitative ultrasound (QUS) of tibial bone speed of sound (SOS). Maternal vitamin D intake, medical history and lifestyle were evaluated from questionnaires. Maternal 25(OH)D levels were deficient (<25 nmol/L) in 24.7%, insufficient (25−50 nmol/L) in 37% and sufficient (>50 nmol/L) in 38.3%. The maternal and cord blood 25(OH)D levels correlated (r = 0.85, p < 0.001). Cord blood levels (57.9 ± 33.5 nmol/L) were higher than the maternal blood levels (46.3 ± 23.2: p < 0.001). The mean SOS was 3042 ± 130 m/s. The neonatal SOS and 25(OH)D levels were not correlated. The mean bone SOS levels were comparable in the three maternal and cord blood 25(OH)D groups. No correlation was found between the maternal 25(OH)D levels and the neonatal anthropometrics. Although the 25(OH)D levels were higher in Jewish mothers than they were in Muslim mothers (51.1 ± 22.6 nmol/L vs. 24 ± 14.7 nmol/L, respectively: p = 0.002) and in those who took supplemental vitamin D, the bone SOS levels were comparable. In conclusion, maternal vitamin D levels correlate with cord levels but do not affect bone strength or growth parameters.

Maternal Diet, Nutritional Status, and Birth-Related Factors Influencing Offspring's Bone Mineral Density: A Narrative Review of Observational, Cohort, and Randomized Controlled Trials

There is growing evidence that bone health may be programmed in the first years of life. Factors during the prenatal period, especially maternal nutrition, may have an influence on offspring’s skeletal development and thus the risk of osteoporosis in further life, which is an increasing societal, health and economic burden. However, it is still inconclusive which early life factors are the most important and to what extent they may affect bone health. We searched through three databases (PubMed, Google Scholar, Cochrane Library) and after eligibility criteria were met, the results of 49 articles were analyzed. This narrative review is an overall summary of up-to-date studies on maternal diet, nutritional status, and birth-related factors that may affect offspring bone development, particularly bone mineral density (BMD). Maternal vitamin D status and diet in pregnancy, anthropometry and birth weight seem to influence BMD, however other factors such as subsequent growth may mediate these associations. Due to the ambiguity of the results in the analyzed studies, future, well-designed studies are needed to address the limitations of the present study.

Feasibility of quantitative ultrasonography for the detection of metabolic bone disease in preterm infants - systematic review

Metabolic bone disease of prematurity is characterised by disordered bone mineralisation and is therefore an increased fracture risk. Preterm infants are especially at risk due to incomplete in utero bone accretion during the last trimester. Currently, diagnosing metabolic bone disease mainly relies on biochemistry and radiographs. Dual-energy x-ray absorptiometry and quantitative ultrasound (US) are used less frequently. However, biochemical measurements correlate poorly with bone mineralisation and although scoring systems exist for metabolic bone disease, radiographs are subjective and do not detect early features of osteopenia. Dual energy x-ray absorptiometry is the reference standard for determining bone density in older children and adults. However, challenges with this method include movement artefact, difficulty scanning small and sick infants and a lack of normative data for young children. Quantitative US has a relatively low cost, is radiation-free and portable, and may hence be suitable for assessing bone status in preterm infants. This review aims to provide an overview of the use of quantitative US in detecting metabolic bone disease in preterm infants.

Quantitative Ultrasound (QUS) in the Management of Osteoporosis and Assessment of Fracture Risk

The use of quantitative ultrasound (QUS) for a variety of skeletal sites, associated with the absence of technology-specific guidelines, has created uncertainty with respect to the application of QUS results to the management of individual patients in clinical practice. However, when prospectively validated (this is not the case for all QUS devices and skeletal sites), QUS is a proven, low-cost, and readily accessible alternative to dual-energy X-ray absorptiometry (DXA) measurements of bone mineral density (BMD) for the assessment of fracture risk. Indeed, the clinical use of QUS to identify subjects at low or high risk of osteoporotic fracture should be considered when central DXA is unavailable. Furthermore, the use of QUS in conjunction with clinical risk factors (CRF),allows for the identification of subjects who have a low and high probability of osteoporotic fracture. Device- and parameter-specific thresholds should be developed and cross-validated to confirm the concurrent use of QUS and CRF for the institution of pharmacological therapy and monitoring therapy.

Vitamin D, the placenta and pregnancy

Impaired vitamin D status is common to many populations around the world. However, data suggest that this is a particular problem for specific groups such as pregnant women. This has raised important questions concerning the physiological and clinical impact of low vitamin D levels during pregnancy, with implications for classical skeletal functions of vitamin D, as well as its diverse non-classical actions. The current review will discuss this with specific emphasis on the classical calciotropic effects of vitamin D as well as the less well established immunological functions of vitamin D that may influence pregnancy outcome. The review also describes the pathways that are required for metabolism and function of vitamin D, and the various clinical complications that have been linked to impaired vitamin D status during pregnancy.

Vitamin D and pregnancy: An old problem revisited

Vitamin D has historically been considered to play a role solely in bone and calcium metabolism. Human disease associations and basic physiological studies suggest that vitamin D deficiency is plausibly implicated in adverse health outcomes including mortality, malignancy, cardiovascular disease, immune functioning and glucose metabolism. There is considerable evidence that low maternal levels of 25 hydroxyvitamin D are associated with adverse outcomes for both mother and fetus in pregnancy as well as the neonate and child. Vitamin D deficiency during pregnancy has been linked with a number of maternal problems including infertility, preeclampsia, gestational diabetes and an increased rate of caesarean section. Likewise, for the child, there is an association with small size, impaired growth and skeletal problems in infancy, neonatal hypocalcaemia and seizures, and an increased risk of HIV transmission. Other childhood disease associations include type 1 diabetes and effects on immune tolerance. The optimal concentration of 25 hydroxyvitamin D is unknown and compounded by difficulties in defining the normal range. Whilst there is suggestive physiological evidence to support a causal role for many of the associations, whether vitamin D deficiency is a marker of poor health or the underlying aetiological problem is unclear. Randomised controlled trials of vitamin D supplementation with an appropriate assessment of a variety of health outcomes are required.