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research letter

Indian Pediatr 2016;53:1023-1024

Vitamin D and Metabolic Bone Parameters in Preterm Neonates


*Amitoj Singh Chhina, Arvind Shenoi, #Namrata Nagendra, Nilesh Rao and Malathi Raja

From the Departments of Neonatology and #Obstetrics and Gynecology, Cloudnine Hospital, Old Airport Road,  Bangalore, Karnataka, India.
Email: [email protected]

 


We measured serum levels of 25-hydroxy vitamin D (25(OH) D) in 79 preterm neonates (
£32 wk), and correlated it with serum ionized calcium (Ca++) levels at 48-72 h and serum phosphorus and alkaline phosphatase levels at 2-3 weeks of age. The mean (SD) 25 (OH)D level was 14.8 (7.0) ng/mL. 25(OH)D levels had a weak positive correlation with Ca++ (r=0.299) and phosphorus (r=0.186), and a negative correlation with alkaline phosphatase (r=-0.523).

Keywords: Hypocalcemia, Neonate, Prematurity.

 


O
steopenia or metabolic bone disease of prematurity has been reported in 55% of extremely low birth weight (ELBW) and 23% of very low birth weight (VLBW) infants [1]. Low phosphorus and high alkaline phosphatase (ALP) are highly sensitive and specific for diagnosing osteopenia of prematurity [1].

Although studies from around the world have reported that preterm infants are deficient in vitamin D at birth [2-6], exact role of active form of vitamin-D in fetal bone mineralization is unclear. Chronic maternal vitamin D deficiency has been shown to adversely affect fetal skeletal development [7]. Preterm infants may have reduced Vit D stores as early delivery may curtail the transplacental transfer that happens between 25 weeks of gestation and term. Maternal deficiency may further restrict the transplacental transfer [7].

We conducted a cross-sectional study at a tertiary-level neonatal unit in Bangalore, Southern India, to determine the 25(OH)D levels of preterm infants £32 weeks at 48-72 hours and correlate them with serum ionized calcium (Ca++) levels at 48-72 hours of life and serum phosphorus and ALP levels at 2-3 weeks postnatal age. The 25(OH)D levels were determined using chemiluminescent microparticle immunoassay (ARCHITECT i1000SR, Abott Diagnostics, Lake Forest, IL, USA). Ca++ levels were measured using potentiometry (Gem Premier 3000, Instrumentation Laboratory, Bedford, MA, USA). Phosphorus levels were measured using spectrophotometry (BioSystems BTS 350, Quezon City, Philippines). ALP levels were determined using absorbance photometry (Cobas C 111, Roche Diagnostics Limited, Rotkreuz, Switzerland).

Seventy-nine preterm neonates were included in the study. The mean (SD) gestational age (GA) and birth weight were 29.8 (2.5) weeks and 1438.1 (464.8) g, respectively. The mean (SD) 25(OH)D level was 14.8 (7) ng/mL (Table I). Forty-eight (60.8%) neonates had Ca++ levels <1 mmol/L, 32 (40.6%) had phosphorus levels <4 mg/dL, and 31 (39.2%) had ALP levels >500 U/L. All the infants had Ca++ ³1 mmol/L at 2-3 weeks. Weak positive correlation was found between 25 (OH) D and Ca++ (r= 0.299, P<0.05), and also 25 (OH) D and phosphorus (r=0.186, P=0.101). Moderate negative correlation was found between vitamin D and ALP (r=-0.523, P<0.05). Weak correlation was also found between GA and 25(OH)D (r=0.422, P<0.05), GA and phosphorus (r=0.495, P<0.05), and GA and ALP (r=-0.523, P<0.05).

TABLE I Serum 25-hydroxy Vitamin D, Calcium and Phosphorus in Preterm Neonates
Characteristics All infants (n=79) Infants born <28 weeks (n=17) Infants 28-32 weeks (n=62)
Males 44 (55.7) 7 (41.2) 37 (59.7)
Gestational age (weeks)* 29.8 (2.5) 25.6 (1.3) 31 (1.2)
Birth weight (g)* 1438.1(464.8) 842.9(168.9) 1601.3 (378.1)
25(OH)D at 48-72 (ng/mL)* 14.8 (7) 10.1 (5.6) 16.1 ( 6.9)
Infants with 25(OH)D <30 ng/mL 78 (99.9) 17 (100) 61 (98.4 )
Infants with 25(OH)D <20 ng/mL 59 (74.7) 16 (94.1) 43 (69.3)
Infants with 25OHD <10 ng/mL 31 (39.2) 10 (58.8) 21 (33.9)
Ca++ at 48-72 hours (mmol/L)* 0.95 (0.13) 0.91 (0.13) 0.96 (0.13)
Phosphorus at 2-3 weeks (mg/dL)* 4.1 (1.1) 3.1 (1) 4.4 (0.9)
ALP at 2-3 weeks (U/L)* 460.7 (160.5) 597 (188.7) 423.3 (138.2)
Values in No. (%) or * mean (SD).

Potential limitations of the study include lack of the maternal 25(OH)D levels and neonatal parathyroid hormone levels; the neonatal 25(OH)D levels at 2-3 weeks; and bone mineral density readings.

Preterm neonates born at £32 weeks, especially <28 weeks tend to have low Vitamin D levels and hypocalcemia at 48-72 hours of life, and may develop hypophosphatemia and elevated ALP levels at 2-3 weeks, but a strong correlation could not be elicited between these parameters.

References

1. Vachharajani AJ, Mathur AM, Rao R. Metabolic bone disease of prematurity. NeoReviews. 2009;10:e402-e11.

2. Natarajan CK, Sankar MJ, Agarwal R, Pratap OT, Jain V, Gupta N, et al. Trial of daily vitamin D supplementation in preterm infants. Pediatrics. 2014; 133:e628-34.

3. Monangi N, Slaughter JL, Dawodu A, Smith C, Akinbi HT. Vitamin D status of early preterm infants and the effects of vitamin D intake during hospital stay. Arch Dis Child Fetal Neonatal Ed. 2014;99:F166-8.

4. Agarwal N, Faridi MM, Aggarwal A, Singh O. Vitamin D status of term exclusively breastfed infants and their mothers from India. Acta Paediatr. 2010;99:1671-4.

5. Dawodu A, Nath R. High prevalence of moderately severe vitamin D deficiency in preterm infants. Pediatr Int. 2011;53:207-10.

6. Burris HH, Van Marter LJ, McElrath TF, Tabatabai P, Litonjua AA, Weiss ST, et al. Vitamin D status among preterm and full-term infants at birth. Pediatr Res. 2014;75:75-80.

7. Dokos C, Tsakalidis C, Tragiannidis A, Rallis D. Inside the "fragile" infant: pathophysiology, molecular background, risk factors and investigation of neonatal osteopenia. Clin Cases Miner Bone Metab. 2013;10:86-90.


 

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