What's new in mother-infant vitamin D deficiency: a 21st century perspective

Post Hoc Analysis of National Institute of Child Health and Human Development Vitamin-D Pregnancy Cohort and The Role of Functional Vitamin-D Deficiency in Pregnancy

OBJECTIVE

Our objective was to conduct a secondary, post hoc analysis of the National Institute of Child Health and Human Development (NICHD) vitamin D (vitD) pregnancy study by Hollis et al, which reported on the effect of vitD supplementation in pregnant women and determine the potential interaction between intact parathyroid hormone (iPTH) concentrations, vitD status, and various comorbidities associated with pregnancy. Women with low 25-hydroxy vitamin D (25(OH)D) concentrations and high iPTH concentrations during pregnancy, known as functional vitamin-D deficiency (FVDD), were more likely to acquire complications also affecting their neonates.

STUDY DESIGN

This post hoc analysis of data collected from a diverse group of pregnant women participating in the NICHD vitD pregnancy study was applied to investigate the applicability of the concept of FVDD in pregnancy (Hemmingway, 2018) in identifying potential risks for certain comorbidities of pregnancy. This analysis defines FVDD as maternal serum 25(OH)D concentrations below 20 ng/mL and iPTH concentrations above 65 pg/mL creating a definitive ratio number, 0.308, to classify mothers as having FVDD prior to delivery (PTD). Statistical analyses were performed using SAS 9.4 (Cary, NC).

RESULTS

In total, 281 women (85 African American, 115 Hispanic, and 81 Caucasian) with 25(OH)D and iPTH concentrations measured at monthly visits were included in this analysis. No statistically significant association was found between mothers classified as having FVDD at baseline or 1-month PTD and hypertensive disorders of pregnancy, infection, or admittance to the neonatal intensive care unit. When combining all comorbidities of pregnancy in this cohort, results showed those with FVDD at baseline, 24 weeks' gestation, and 1-month PTD were more likely to experience a comorbidity (p = 0.001; p = 0.001; p = 0.004, respectively). Those with FVDD 1-month PTD were 7.1 times (confidence interval [CI]: 1.71-29.81) more likely to have preterm birth (<37 weeks) than women without FVDD.

CONCLUSION

Participants were more likely to have experienced preterm birth if they met the criteria for FVDD. This study supports the importance of FVDD during pregnancy.

KEY POINTS

· Functional vitamin D deficiency (FVDD) is defined as the ratio of 25(OH)D divided by iPTH concentration ≤0.308.. · At a minimum, it is recommended that vitamin D status be kept in the healthy range based on current recommendations for pregnant individuals.. · FVDD is a more sensitive predictor of pregnancy risk than 25(OH)D alone.. · FVDD identified those with greater risk of preterm birth in this cohort..

Effect of Vitamin D Supplementation on (25(OH)D) Status in Children 12-30 Months of Age: A Randomized Clinical Trial

Vitamin D (VD) deficiency (serum 25(OH)D < 50 nmol/L) affects 27.3% of preschool children in Mexico. The purpose of this study was to assess the effect of vitamin D supplementation at different doses on serum 25(OH)D concentrations in preschool children. In a randomized control trial, 222 children 12-30 months old were randomly assigned to one of four treatment groups: (1) Vitamin D2 (Ergocalciferol) 400 IU/day (n = 56); (2) Vitamin D2 (Ergocalciferol) 800 IU/day (n = 55); (3) Vitamin D3 (Cholecalciferol) 1000 IU/day (n = 56); or (4) multiple micronutrients (MM) non-VD (n = 55). Supplements were given five days/wk for three months. Serum 25(OH)D was measured at baseline and after three months. At baseline, mean serum 25(OH)D was 58.9 ± 12.6 nmol/L and 23.4% were VD-deficient. There was a statistically significant increase in serum concentrations of 25(OH)D (range across groups: +8.2 to +17.3 nmol/L). Additionally, the prevalence of vitamin D deficiency decreased after three months: for D2 400 IU, -9.0%; for D2 800 IU, -11.0%; for D3 1000 IU, -18.0%; and for MM non-VD, -2.8% (p < 0.05). No adverse effects were observed. VD supplementation for three months was effective for increasing serum 25(OH)D concentrations and for reducing VD deficiency in preschool children. The highest efficacy was observed by giving 1000 IU D3/d.

Evaluating Vitamin D Status in Infants Less than Seven Months; What Are the Preferred Biochemical Measurements?

Background: To ensure the safety of higher dose vitamin D supplementation in pregnant and lactating mothers, and urinary calcium/creatinine (UCa/Cr) ratios, serum calcium, and serum 25(OH)D concentrations are closely monitored. To achieve optimal maternal and infant vitamin D status, while avoiding hypercalcemia, safety measures assessing vitD supplementation must be reliable. Whether or not this holds true for infants before 7 months of age, remains unknown. Objective: Analyze the association among UCa/Cr ratio, serum calcium, intact serum parathyroid hormone (iPTH), 25(OH)D, and 25(OH)D/iPTH ratio in infants to determine whether evidence supports the use of these parameters as valuable measures of hypervitaminosis D or toxicity in infants. Methods: A series of analyses were performed on the cohort of infants who participated in the National Institute of Child Health and Human Development lactation vitD supplementation trial to determine the association among UCa/Cr ratio, serum calcium, iPTH, 25(OH)D, and 25(OH)D/iPTH ratio. Results: Upon multivariate analysis, serum calcium was significantly associated with 25(OH)D (p = 0.0441), iPTH (p = 0.0017), and 25(OH)D/iPTH ratio (p = 0.0001). Infant UCa/Cr did not associate with 25(OH)D but did associate with iPTH (p = 0.0008) and 25(OH)D/iPTH ratio (p = 0.0001). The correlation between UCa/Cr and 25(OH)D/iPTH ratios was significantly stronger than the association between UCa/Cr ratio and iPTH. Serum calcium more strongly correlated with 25(OH)D/iPTH ratio versus 25(OH)D and iPTH. Conclusion: In this healthy cohort of infants 1 to 7 months old, UCa/Cr and serum calcium are more valid indicators of 25(OH)D/iPTH ratio than either 25(OH)D or iPTH alone. Moreover, serum calcium (and not UCa/Cr) is a valid indicator of infant total circulating 25(OH)D and should be measured if vitamin D toxicity is a concern. Clinical Trial Registration number: FDA IND Number: 66,346; ClinicalTrials.gov Number: NCT00412074.

Health characteristics and outcomes of two randomized vitamin D supplementation trials during pregnancy: a combined analysis

OBJECTIVE

To assess the safety and health effects of vitamin D supplementation during pregnancy.

METHODS AND DESIGN

Datasets from two randomized clinical trials were first analyzed separately then combined for this analysis using a common data dictionary. In the NICHD trial, women were randomized to 400, 2000, or 4000IU vitamin D3/day, stratified by race. In the Thrasher Research Fund trial, participants were randomized to 2000 or 4000IU vitamin D3/day. Study drugs were from the same manufacturing lot for both trials. Identical questionnaires were given for comparable sociodemographics & clinical characteristics. Outcome measures were: [1] maternal and neonatal 25(OH)D achieved, and [2] maternal comorbidities of pregnancy (COP). SAS 9.3 was used for all analyses.

RESULTS

In the combined cohort, there were 110 controls, 201 in the 2000IU group, and 193 in the 4000IU group. No differences between groups in baseline 25(OH)D were found; however, delivery and cord blood values were greater in the 4000IU group (p<0.0001), an effect that persisted even after controlling for race and study. A greater percent were vitamin D replete in the 4000IU group (p<0.0001). There was a trend where the 4000IU group had decreased rates of comorbidities of pregnancy. There was a strong association between COP and final maternal 25(OH)D; an effect that persisted even after controlling for race and study (p=0.006).

CONCLUSIONS

Supplementation with 4000IU/day was associated with lower risk of hypovitaminosis D than Control and 2000IU groups. While not statistically significant, there was a trend toward lower rates of COP as supplementation dose increased. Maternal delivery 25(OH)D was inversely associated with any comorbidity of pregnancy, with fewer events as 25(OH)D increased. Future studies are needed to confirm these findings and determine the mechanisms of action of such effects. This article is part of a Special Issue entitled 'Vitamin D Workshop'.