Changes in body temperature and urinary cortisol after routine immunization in babies with intrauterine growth retardation

Aim: To investigate whether infants with intrauterine growth retardation (I UGR) experience different changes in temperature and cortisol excretion aft er routine immunization compared with normal healthy infants. Methods: Over night deep body temperature and urinary cortisol to creatinine ratios were measured on the night after immunization and a control night in normal and IUGR infants. Results: In 60 normal infants, first vaccination at about 10 wk of age led to a significant increase in minumum overnight temperature co mpared to the control night, mean rise 0.25 degreesC (95% CI, 0.12 to 0.38) . In 35 IUGR infants the mean rise in temperature between immunization nigh t and control night was 0.35 degreesC (95% CI, 0.15 to 0.55). The increases in minimum temperature did not differ significantly between the normal and IUGR infants (p = 0.11). Cortisol to creatinine ratios measured from overn ight urine samples showed that 23 IUGR infants had consistently higher leve ls than 39 normal infants; control night medians 34 and 15 (p = 0.01) and i mmunization night medians 56 and 26 (p=0.02), respectively. However, the pe rcentage increase did not differ significantly between the IUGR infants and the normal infants. A smaller number of second immunizations were studied, but no significant differences were found. Conclusion: These results suggest that although the impact of immunization is the same for IUGR and normal infants, because IUGR infants are less matu re and at greater stress before immunization, the absolute levels that they experience after immunization are higher than those for normal infants.