Influence of umbilical cord vitamin D serum levels on the growth of preterm infants.

OBJECTIVE: The aim of this study was to evaluate the influence of serum 25-hydroxyvitamin D [25(OH)D] levels at birth in postnatal growth at discharge and 12 mo of corrected age in preterm infants. METHODS: This prospective cohort included 63 preterm newborns born before 34 gestational weeks evaluated from birth until 12 mo of corrected age. The serum 25(OH)D levels in umbilical cord blood and from their mothers were evaluated at delivery. RESULTS: The mean 25(OH)D levels in preterm newborns were higher than maternal levels (24.8 ± 13.3 ng/mL versus 21 ± 10.2 ng/mL, P < 0.001) and showed a moderate correlation between (r = 0.548; P < 0.001). Considering the body mass index Z-score at 12 mo, 3 (10%), 25 (83%), and 2 (7%) of the preterm infants were thin, had normal body mass index, and were overweight, respectively. The 25(OH)D levels in the umbilical cord did not influence the anthropometric indicators at hospital discharge and 12 mo of corrected age. We observed improvement in all anthropometric indicators assessed over the months, and there was no difference between preterm infants with 25(OH)D levels >20 ng/mL and <20 ng/mL in the umbilical cord. CONCLUSIONS: The results of this study suggested that the 25(OH)D serum levels in the umbilical cord did not influence postnatal growth from birth to the first year of life in preterm infants. There was a direct association between maternal and umbilical cord serum 25(OH)D levels.

Association between vitamin D plasma concentrations and VDR gene variants and the risk of premature birth.

BACKGROUND: Premature birth is the main cause of mortality in children under 1 year, and vitamin D deficiency during gestation is associated with prematurity. The effects of vitamin D are mediated by its receptor, which is encoded by the VDR gene. VDR variants-such as single nucleotide variation (SNV)-are associated with increased risk of prematurity, but there are conflicting results. We evaluated serum vitamin D concentrations and the frequency of TaqI/A > G, BsmI/C > T, ApaI/C > A, and FokI/A > T VDR variants in mothers and preterm (PTN) and full-term (FTN) newborns. METHODS: We conducted a case-control study comprising 40 pairs of mothers and their PTNs (gestational age < 32 weeks and/or weight < 1500 g), and 92 pairs of mothers and FTNs as controls. Genotyping was performed by real-time PCR, and plasma vitamin D concentrations were measured by electrochemiluminescence. RESULTS: Vitamin D levels were significantly lower in PTN mothers. Genotypes TaqI/GG and BsmI/TT, and haplotypes AAG (TaqI/A-ApaI/A-FokI/G) and GCA (TaqI/G-ApaI/C-FokI/A) were significantly more frequent in PTN mothers, and genotypes TaqI/AG, ApaI/AA, and FokI/AG resulted in significantly lower vitamin D levels. Genotypes BsmI/TT and ApaI/AA were associated with vitamin D deficiency and 2.36 and 7.99 times greater likelihood of PTB, respectively. Vitamin D levels were also lower in PTNs, although it was not statistically significant. Genotypes BsmI/TT, ApaI/AA, and FokI/GG, and haplotype GAG (TaqI/G-ApaI/A-FokI/G) were significantly more frequent in PTNs. Those with FokI/GG genotypes had significantly lower vitamin D levels. CONCLUSIONS: VDR variants contribute to variations in vitamin D concentrations and the increased risk of prematurity.

Vitamin D plasma concentrations in pregnant women and their preterm newborns.

BACKGROUND: Vitamin D deficiency is a global public health issue. More than half of pregnant women are affected by vitamin D insufficiency/deficiency. Studies suggest an association between low vitamin D concentrations during pregnancy with intrauterine growth restriction and prematurity. This study aimed to describe the concentrations of 25(OH)D (25-hydroxyvitamin D) of mothers who delivered preterm newborns compared to women with full-term pregnancy deliveries, as well as to relate 25(OH)D blood concentrations of mothers with those of their newborns. METHOD: This cross-sectional study was conducted with 66 mothers who had given birth to preterm babies and their preterm newborns (PTNB, < 32 weeks), and 92 women who had given birth at the full-term of their pregnancy and their newborns (FTNB). Data were collected on the characteristics of mothers (gestational age, diseases, and habits) and newborns (anthropometry and adequacy for gestational age). Ten milliliters of blood were drawn from the mothers and the umbilical cord of newborns at birth to identify the 25(OH)D, parathyroid hormone, calcium, phosphorus, and alkaline phosphatase concentrations. RESULTS: Mothers in the PTNB group had significantly lower mean 25(OH)D blood levels (21.7 ± 10.8 ng/mL vs. 26.2 ± 9.8 ng/mL; p = 0.011) and were three times more likely to have insufficiency when compared to mothers in the FTNB group (OR = 2.993; 95%CI 1.02-8.74). Newborns in the PTNB group also had lower 25(OH)D concentrations compared to FTNB group (25.9 ± 13.9 ng/dL vs. 31.9 ± 12.3 ng/dL; p = 0.009). There was a directly proportional correlation between mother and newborn umbilical cord 25(OH)D concentrations in PTNB (r = 0.596; p <  0.001) and FTNB (r = 0.765; p <  0.001). CONCLUSION: Mothers who delivered preterm babies and their preterm newborns had lower 25(OH)D concentrations compared to women who had given birth at the full-term of their pregnancy. In both groups, 25(OH)D concentrations of the mothers correlated directly with those of the newborns, and this correlation was higher in the full-term birth group. Nevertheless, the recommended universal vitamin D supplementation in pregnant women to curb the risk of preterm birth is still incipient. More studies are required to clarify the particularities of vitamin D metabolism further and define the adequate 25(OH)D concentrations throughout pregnancy.