Vitamin D inadequacy in pregnancy: biology, outcomes, and interventions

Vitamin D - roles in women's reproductive health?

In the past few years a growing interest in vitamin D can be observed in the lay and biomedical literature due to findings demonstrating a low vitamin D status in the population. In addition to its importance for the regulation of calcium and phosphorus homeostasis recent epidemiologic studies have observed relationships between low vitamin D levels and multiple disease states. This secosteroid hormone also regulates the expression of a large number of genes in reproductive tissues implicating a role for vitamin D in female reproduction. In this report we summarize the recent evidence that vitamin D status influences female reproductive and pregnancy outcomes. Human and animal data suggest that low vitamin D status is associated with impaired fertility, endometriosis and polycystic ovary syndrome. Evidence from observational studies shows higher rates of preeclampsia, preterm birth, bacterial vaginosis and gestational diabetes in women with low vitamin D levels. However, confirmation of experimental observations establishing an association of vitamin D deficiency with adverse reproductive outcomes by high quality observational and large-scale randomized clinical trials is still lacking. The determination of optimal 25(OH)D3 levels in the reproductive period and the amount of vitamin D supplementation required to achieve those levels for the numerous actions of vitamin D throughout a woman's life would have important public health implications.

Relationship of maternal vitamin D level with maternal and infant respiratory disease

OBJECTIVE

The objective of the study was to investigate the association of maternal vitamin D and maternal asthma and infant respiratory infection severity.

STUDY DESIGN

The study included cross-sectional analyses of 340 mother-infant dyads enrolled from September to May 2004-2008 during an infant viral respiratory infection. Maternal vitamin D levels were determined from enrollment blood specimens. At enrollment, we determined self-reported maternal asthma and infant respiratory infection severity using a bronchiolitis score. We assessed the association of maternal vitamin D levels and maternal asthma and infant bronchiolitis score in race-stratified multivariable regression models.

RESULTS

The cohort was 70% white, 19% African American, and 21% had asthma. Overall, the median maternal vitamin D level was 20 ng/mL (interquartile range, 14-28). Among white women, a 14 ng/mL increase in vitamin D was associated with a decreased odds of asthma (adjusted odds ratio, 0.54; 95% confidence interval, 0.33-0.86). Maternal vitamin D was not associated with infant bronchiolitis score.

CONCLUSION

Higher maternal vitamin D levels were associated with decreased odds of asthma.

Maternal vitamin D and fetal growth in early-onset severe preeclampsia

OBJECTIVE

Recently, vitamin D deficiency has been associated with increased risks for preeclampsia and diagnosis of early-onset, severe preeclampsia (EOSPE). The purpose of this investigation was to examine the association between vitamin D levels and small-for-gestational age (SGA) in patients with EOSPE.

STUDY DESIGN

Patients with EOSPE were recruited, and demographics, outcomes, and plasma were collected. We assessed 25-hydroxyvitamin D (25[OH]D) by radioimmunoassay and reported our findings in nanograms per milliliter. Results were analyzed by Mann-Whitney U test and Spearman correlation and were reported as median (Q1-Q3).

RESULTS

In patients with EOSPE (n = 56), 25(OH)D was lower in patients with SGA (16.8 ng/mL; range, 8.9-23 ng/mL) vs normal fetal growth (25.3 ng/mL; range, 16-33 ng/mL; P = .02). 25(OH)D was correlated significantly with percentile growth at delivery (ρ = 0.31; P = .02).

CONCLUSION

Vitamin D is lower among patients with SGA in EOSPE than those without growth retardation. We suspect that vitamin D may impact fetal growth through placental mechanisms.

Early nutritional predictors of long-term bone health in preterm infants

PURPOSE OF REVIEW

Early life nutrition may influence later osteoporosis risk. Preterm infants are at particular risk of suboptimal early nutrition, which is associated with poor neonatal bone mineralization and metabolic bone disease, but it is unclear whether this has long-term consequences for bone health. This review discusses the long-term effects of early diet in patients born preterm who participated in a nutritional intervention trial during the neonatal period and the role of vitamin D in this population.

RECENT FINDINGS

Available data suggest that, despite large differences in neonatal mineral intake, no effect of neonatal diet on bone mass or bone turnover is detectable in early adult life. However, greater exposure to human milk in the neonatal period, despite its very low mineral content, is associated with higher peak bone mass. Studies in healthy term infants suggest that suboptimal maternal vitamin D status during pregnancy has adverse effects on offspring bone health in infancy and later childhood; however, effects in infants born preterm have not been investigated.

SUMMARY

The findings suggest that early mineral intake may not influence later bone mass, with implications for the setting of recommended mineral intakes for contemporary preterm infants; these are currently high and based on achieving in-utero mineral accretion rates rather than on clinical outcome. Despite its low mineral content, human milk, perhaps via a non-nutrient effect, may have long-term benefits for bone health adding to other health benefits already identified in this vulnerable population. The role and optimal dose of vitamin D for later bone health in preterm infants requires further research.

Developmental vitamin D deficiency and risk of schizophrenia: a 10-year update

There is an urgent need to generate and test candidate risk factors that may explain gradients in the incidence of schizophrenia. Based on clues from epidemiology, we proposed that developmental vitamin D deficiency may contribute to the risk of developing schizophrenia. This hypothesis may explain diverse epidemiological findings including season of birth, the latitude gradients in incidence and prevalence, the increased risk in dark-skinned migrants to certain countries, and the urban-rural gradient. Animal experiments demonstrate that transient prenatal hypovitaminosis D is associated with persisting changes in brain structure and function, including convergent evidence of altered dopaminergic function. A recent case-control study based on neonatal blood samples identified a significant association between neonatal vitamin D status and risk of schizophrenia. This article provides a concise summary of the epidemiological and animal experimental research that has explored this hypothesis.