Effects of gestation age and of birth weight in the concentration of carnitine in the umbilical plasma.

To investigate the factors which affect the concentrations of the total, the free, and the acylcarnitine in neonates, blood was taken from the umbilical cord of 49 newborn infants ranging in gestation age (g. a.) from 32-40 weeks (mean g. a.: 36.8 +/- 2.6 weeks) and in birth weight (b. w.) from 1300 gr.-4300 gr. (mean b. w.: 2299 +/- 457 gr.). The carnitine and its fractions were studied in plasma. Twenty-eight of the neonates studied were premature (g. a. 37 weeks). The concentration of the total, free, and acylcarnitine in premature neonates was 28.0 +/- 2.3 mumol/L, 15.9 +/- 1.3 mumol/L, and 12.0 +/- 1.3 mumol/L, respectively. For the full-term neonates the respective concentrations were: 25.2 +/- 2.2 mumol/L, 14.6 +/- 1.5 mumol/L, and 10.7 +/- 1.5 mumol/L. These differences in concentrations between premature and full-term infants were statistically significant. For the total number of neonates studied the concentration of total, free, and of acylcarnitine was 26.8 +/- 2.6 mumol/L, 15.3 +/- 1.9 mumol/L, 11.5 +/- 1.5 mumol/L respectively. The calculation of the correlation coefficients for the total number of neonates showed the existence of a statistically significant negative correlation between the total, free and acetyl carnitine in terms of gestation age and birth weight. The comparative analysis of the correlation coefficients showed greater coefficient values between the total and the acylcarnitine in terms of birth weight. The latter finding, combined with the low rate of acylcarnitine decline, are indirect indications that the fetus uses carnitine as a source of energy, which affects the levels of total and acylcarnitine in the plasma.