Results of extremely-low-birth-weight infants randomized to receive extra enteral calcium supply

Abstract

Background and objective: Bone mineral deficiency continues to occur in extremely-low-birth-weight (ELBW) infants despite formulas enriched in calcium (Ca) and phosphorus (P). This study tested whether extra enteral Ca supplementation increases bone mineral content (BMC) and prevents dolichocephalic head flattening and myopia in ELBW infants.

Study design: Infants 401 to 1000 birth weight receiving enteral feeds were randomized to receive feeds supplemented with Ca-gluconate powder or pure standard feeds. The main outcome measures were the excretion of Ca and P by weekly spot urine measurements, the degree of dolichocephalic deformation (fronto-occipital diameter to biparietal diameter ratio, FOD/BPD) at 36 weeks postmenstrual age, and the BMC (by dual-energy x-ray absorptiometry) at discharge. Cycloplegic refraction was measured at 18 to 22 months corrected age.

Patients and results: Ninety-nine ELBW infants with a gestational age of 26 weeks (23-31) (median [minimum-maximum]) were randomized at a postnatal age of 12 days (5-23) weighing 790 g (440-1700). Urinary Ca excretion increased and P excretion decreased in the Ca-supplemented group. Total BMC was 89.9 ± 2.4 g (mean ± SE) in the supplemented group and 85.2 ± 2.6 g in the control group (P = 0.19). The FOD/BPD was 1.50 (1.13-1.69, mean ± SD [standard deviation]) and 1.47 (1.18-1.64) in the supplemented and control groups, and the refraction 0.98 ± 1.23 and 1.40 ± 1.33 dpt (P = 0.68), respectively in 64 ELBW infants (79% of survivors) at 2-year follow-up.

Conclusions: Extra enteral Ca supplementation did not change BMC, head shape, or refraction. The decreased P excretion may reflect P deficiency in infants receiving extra Ca, preventing improved bone mineral accretion.

Trial registration: ClinicalTrials.gov NCT00892476.

Fig. 1

The trial profile. Dual energy x-ray absorptiometry (DXA) scans were unreadable in 3 patients because of movement artifacts. DXA scanning was not possible in 11 patients because they were discharged from another hospital and did not return. These infants did not differ from the rest in any demographic characteristic. NEC = necrotizing enterocolitis.

Fig. 2

Ca and P in spot urine samples. Median values of each patient’s percentage of urine samples containing more than 1 mmol/l Ca, P or both are shown. Error bars represent 25^th –75^th percentile. Asterisks indicate values significantly different by a Mann-Whitney U test (p < 0.02).