Metabolic bone disease in exclusively breast fed very low birth weight infants

Metabolic bone disease (MBD) or rickets is frequent in very low birth weight infants. A descriptive cross- sectional hospital based study was carried out from April to June 1995 to find out the magnitude, contributory factors, morbidity and suitable biochemical diagnostic tests for MBD. The outcome of this study was expected to show whether calcium and phosphate supplementation was indicated in exclusively breast fed VLBW infants. 100 infants at the postnatal age of 6-12 weeks with birth weight of 1500g or less were studied. The health status of the infants was assessed by thorough history and physical examination. Double view radiography of left wrist was done on all infants and serum calcium, phosphate and alkaline phosphatase were determined. The radiography was used to identify presence or absence of MBD. 33 out of 100 (33%) infants, 16 males and 17 females were diagnosed to have metabolic bone disease radiographically. The mean gestational age of the infants with metabolic bone Vll III disease was 30.4 weeks (SD=2. 7 weeks) while that of the infants without metabolic bone disease was 32.4 weeks (SD=3 weeks) (P value=0.003). There was no significant difference in birth weight between infants with MBD and infants without MBD. However, the postnatal weight was significantly different. Infants with MBD weighed 2955.5g to 5660g, while infants without MBD weighed 1170g to 3700g (P=0.008). The mean postnatal octopi-frontal circumference was 35.6cm (SD=2.8) in infants with metabolic bone disease and 34.2cm (SD=3.4) in infants without metabolic bone disease(P value=0.053) . The mean length was 47.7cm (SD=5) and 45.0cm (SD=4.3) in infants with metabolic bone disease and in infants without metabolic bone disease respectively (P value=0.006). No significant difference in serum calcium and phosphate was observed between infants with MBD and those without MBD. The mean serum alkaline phosphatase was 1052.9iu/L (SD=493.3iu/L) in infants with metabolic bone disease and 766.8iu/L (SD=301.7iu/L) in infants without metabolic bone 'disease (P value=0.006). lV MBD was not affected by parity or multiple delivery. It is concluded that metabolic bone disease is common in very low birth weight infants. Hence calcium and phosphate supplementation intervention study should be done to find out its effect on MBD incidence