Getting rhythm: how do babies do it?

OBJECTIVES: To investigate the emergence of biological rhythms in the first months of life in human infants, by measuring age-related changes in core body temperature during night-time sleep, hormones (cortisol and 6-sulfatoxymelatonin) and the expression of a clock-controlled gene H3f3b in oral epithelial cells. DESIGN: Observational longitudinal study. SETTING: We measured overnight core body temperature, actigraphy, day-night urinary cortisol and 6-sulfatoxymelatonin, as well as circadian gene expression, in infants at home from March 2007 to July 2008 in Leicester. PARTICIPANTS: We recruited 35 healthy Caucasian infants who were born at term. They were monitored from 6 to 18 weeks of age. RESULTS: At 8 weeks of age the day-night rhythm of cortisol secretion was the first to appear followed by 6-sulfatoxymelatonin 1 week later; at the same time that night-time sleep was established. At 10 weeks, the maximum fall in deep body temperature occurred with the onset of night-time sleep, followed at 11 weeks by the rhythmical expression of the H3f3b gene. CONCLUSIONS: In human infants, there is a clear sequential pattern for the emergence of diurnal biological rhythms between 6 and 18 weeks of postnatal age, led by the secretion of cortisol and linked with the establishment of consolidated night-time sleep. It is likely that this represents part of a maturation and adaption process as infants gain equilibrium with their external environment after birth.

Heart rate variability analysis of normal and growth restricted children.

INTRODUCTION: Intrauterine growth restriction (IUGR) has been associated with an increased risk of cardiovascular disease in later life. The regularity mechanism of cardiovascular system is under the control of autonomic nervous system (ANS). The non-optimal fetal growth may alter the development of the ANS and this appears to persist in later life. The aim of the present work is to analyse the synergic activity of the ANS in normal and growth restricted children. MATERIAL AND METHODS: Heart rate variability analysis from 24 h ECG recordings of 70 children between 9 and 10 years old, normal and IUGR was performed using linear and non-linear time series analysis techniques. CONCLUSION: The HRV parameters showed no significant difference between normal and IUGR children. Low birth weight and its association with development of the cardiovascular system and its control have been extensively studied. In order to investigate the effect of low birth weight on HRV parameters, the IUGR children were further divided into two groups: IUGR-1 (birth weight<2.50 kg) and IUGR-2 (birth weight≥2.50 kg). The results demonstrated that most of the HRV measures showed significant differences between normal versus IUGR-1 as well as IUGR-1 versus IUGR-2 groups. The effect of gender on HRV measures was also examined and we noticed that girls had lower HRV than boys.

Fetal growth restriction: relation to growth and obesity at the age of 9 years.

OBJECTIVE: To assess growth patterns of 9-year-old children, some of whom had intrauterine growth restriction (IUGR). METHOD: 75 9-year-old children (41 were IUGR infants) were weighed and measured at birth, at 1 year, at 2 years and at 9 years of age. Using general linear models for continuous data, changes in weight z scores were used to quantify growth rate between birth and 9 years of age. RESULTS: IUGR children were smaller at birth (weight z score -2.1 v 0.2 in normal children; p<0.001) but showed a greater increase in their weight between birth and 9 years (change of weight z score 1.5 v 0.4 in normal children; p = 0.001). At the age of 9 years the weight, height and body mass index (BMI) z scores were lower in IUGR children than the control children (weight z score -0.4 v 0.6, respectively; p<0.001, height z score -0.5 v 0, respectively; p = 0.002, BMI z score -0.2 v 0.7, respectively; p = 0.002). The predictors of these differences were IUGR, birth weight and maternal and paternal heights. CONCLUSION: IUGR infants grow faster but remain shorter and lighter than their normal counterparts-that is, they fail to fully catch up by 9 years of age.