BONE-MINERAL DEFICIENCY AS THE MAIN FACTOR OF DOLICHOCEPHALIC HEAD FLATTENING IN VERY-LOW-BIRTH-WEIGHT INFANTS

We hypothesized that the postnatally reduced rate of bone mineralizati on observed in many very-low-birth-weight (VLBW) infants is the main c ause of dolichocephalic flattening of the head in this group of newbor ns. We measured head shape by using the ratio of the frontooccipital a nd biparietal diameters, bone mineral content (BMC) at the right midhu merus, birth weight, body weight, and postnatal age at the time of BMC measurement in 85 newborn infants during the first 5 d of life (gesta tional age: median 34 wk, range 24-40 wk; birth weight: median 1.590 g , range 430-6.730 g) and in 269 VLBW infants at transfer to other hosp itals or discharge. The head shape shortly after birth was not influen ced by gestational age. Mean frontooccipital diameter/biparietal diame ter was 1.27 +/- 0.73 SD (range 1.13-1.59). Stepwise multiple regressi on analysis from 315 measurements made in 46 VLBW infants during the f irst 5 d after birth and the 269 infants at discharge revealed a 27% c ontribution of BMC/body weight to the variation in head shape. The oth er variables had only a small effect (gestational age 4%, body weight 1%) or no observable effect on head shape. At discharge, the ratio of BMC to body weight was significantly lower than in the reference fetus es of the same body weight. The results support the hypothesis, and we speculate that there is a causal relationship between the head shape of VLBW infants at discharge and the amount of calcium and phosphorus given as a supplement until that time.