[Examination of infant bone status with quantitative ultrasound at birth].

OBJECTIVE

Quantitative ultrasound (QUS) is a new method of evaluating Children's bone status, including bone mineral density and bone strength. The bone nutrition during fetal and early neonatal period is very important for the human bone development of whole life. The objective of this study was to evaluate the clinical application of QUS for newborn infants and to obtain the QUS data for normal neonates including premature infants.

METHODS

An ultrasound bone sonometer, Omnisense, produced by Sunlight company of Israel, was applied to measure the bone speed of sound (SOS) of tibia in 157 neonates including 68 premature infants in the first week of life.

RESULTS

(1) No significant difference in SOS was found between male (n = 88, SOS = 2968 +/- 115 m/s) and female infants (n = 69, SOS = 2956 +/- 105 m/s) (P = 0.524). The SOS of premature infants (n = 68, mean gestational age 33.0 +/- 2.5 weeks) and full-term infants (n = 89, mean gestational age of 39.4 +/- 1.3 weeks) were 2935 +/- 96 m/s and 2984 +/- 116 m/s, respectively, at birth and there was significant difference between them (P = 0.005). (2) There were significant differences of SOS in neonates who were born in different seasons (F = 4.377, P = 0.005); the significant difference remained (F = 3.933, P = 0.010) after the influences of gestational age and birth weight were eliminated. The SOS in neonates born in spring (March, April and May) and summer (June, July and August) were significantly lower than that of those born in autumn (September, October and November) and winter (December, January and February). The SOS in neonates born in summer was about 2.3% (75/2999) was lower than that of those born in winter. (3) Significant difference of SOS was observed between neonates with different birth weight [< 1500 g (n = 11), SOS = 2968 +/- 115 m/s; and > 2500 g (n = 86), SOS = 2980 +/- 113 m/s; P = 0.042]. (4) Significant correlations were found between SOS and gestational age (r = 0.270, P = 0.005), and between bone SOS and birth weight (r = 0.232, P = 0.015) in appropriate for gestational age (AGA) infants (n = 109); however, no such significant correlations were found in small for gestational age (SGA) infants or large for gestational age (LGA) infants. Multiple regression analysis showed that gestational age and the birth season were two important factors which may contribute to bone SOS of neonates at birth (n = 157, F = 8.515, P < 0.001, adjusted R(2) = 0.141), when the analysis was carried out with SOS as dependent variable and gestational age, birth weight, chronological age, calf length and the birth season as independent variables.

CONCLUSION

QUS is a new method which is suitable for evaluating the bone status of neonates and it is free of radiation, non-invasive, the machine is portable and easy to manipulate at infant bed side. The present study suggests the need for particular care for the bone status in premature infants and supplement of vitamin D in pregnant women.