Background Serum alkaline phosphatase levels (S-ALP) are often high among extremely preterm babies before first two weeks of life. It is not certain whether this represents increased physiological bone turn-over or is a predictor for osteopenia of prematurity.

Aim To study the relationship between osteopenia of prematurity and peak S-ALP levels with in first two weeks among pre-term babies born before twenty-nine weeks gestation.

Methods We evaluated seventy-three extremely pre-term babies born before twenty-nine weeks gestation who were admitted to tertiary neonatal units in Leeds, UK from 01/01/2009 to 31/01/2011. S-ALP, calcium and inorganic phosphate were checked regularly while they were in the neonatal unit. Forty out of seventy three babies had radiographs performed after five weeks post-natal age and were reported by radiologist.

Results In our cohort of seventy-three extremely pre-term babies, 55% had peak S-ALP levels exceeding 1200 iu/l (four times the upper limit of normal for adults) with in first two weeks. Infants who developed osteopenia had significantly lower gestational age and birth weight, and were significantly more likely to receive post-natal steroids. Radiologically proven osteopenia developed in 74% of infants with peak S-ALP exceeding 1200 iu/l compared to 35% of infants with peak S-ALP below 1200 iu/l before two weeks post-natal age (p-value 0.014).

Conclusion S-ALP exceeding 1200 iu/l with in two weeks post-natal age is associated with 2.1 fold increased risk of development of osteopenia in extremely pre-term infants.