Fat mass in infants and toddlers: comparability of total body water, total body potassium, total body electrical conductivity, and dual-energy X-ray absorptiometry.

BACKGROUND: Accurate assessment of body composition in infants and children is fundamental to understanding normal growth and development. Validation of methods applicable to pediatric populations is needed. In the absence of a gold standard, this study was conducted to compare methods using total body water, total body potassium, total body electrical conductivity, and dual-energy x-ray absorptiometry measurements for the estimation of body fat mass in infants and toddlers. METHODS: Repeated body composition measurements were performed on 76 healthy term infants at 0.5, 3, 6, 9, 12, 18, and 24 months of age. Total body water was determined by deuterium dilution and converted to fat-free mass. Total body electrical conductivity was used to measure fat mass. Total body potassium was estimated by whole-body counting and converted to fat-free mass. Dual-energy x-ray absorptiometry was used to estimate fat mass at 0.5, 12, and 24 months only. Data were analyzed by repeated measures analysis of variance, followed by Bonferroni multiple comparisons at 5%. RESULTS: Significant differences among methods were encountered at each age (p = 0.001-0.05). The rank order of the methods and the magnitude of the method differences were a function of age, not of gender or infant feeding mode. Wide limits of agreement imply that the methods are not interchangeable for group or individual measurements. CONCLUSIONS: Methods using total body water, total body potassium, total body electrical conductivity, and dual-energy x-ray absorptiometry to estimate body fat mass in infants and toddlers are not interchangeable and require further development and validation.     

Two-dimensional and M-mode assessment of aortic growth in the normal and growth-retarded (IUGR) human fetuses

Summary This study compares human fetal aortic dimensions in 128 normal and 30 intrauterine growth-retarded (IUGR) fetuses using two-dimensional (2D) and M-mode echocardiography. We found that the fetal aortic root in the normally grown fetuses is significantly larger than the descending aorta at all gestational ages. Furthermore, IUGR fetuses had smaller descending aortic dimensions then did normally grown fetuses. When the descending aortic dimension in the IUGR fetuses was corrected for estimated fetal weight, it was found to be of comparable size to those of the normal fetuses. The difference in aortic size of growth-retarded fetuses is proportional to growth and therefore probably a secondary phenomenon.     

Determination of body composition in growing rats by total body electrical conductivity.

Total body electrical conductivity (TOBEC), measured with an Em-Scan SA-1 analyzer, was evaluated as a means of estimating fat-free mass and total body water content noninvasively in small laboratory animals. Ninety-four rats whose weight ranged from 5.53 to 170.84 g at 0-50 days of age were studied. The animals were killed by intraperitoneal injection of a pentobarbital overdose. After weight, crown-rump length (CRL) and TOBEC were measured, and the animals were minced with scissors and desiccated to constant weight in a convection oven. Fat was extracted by multiple bathings in petroleum ether followed by Soxhlet extraction. Fifty-four rats were used to determine the relation between fat-free mass (FFM), total body water (TBW), and TOBEC# (E) by regression analysis. The best correlations were observed between FFM and (E x CRL)1/2 (r = 0.995, p less than 0.0001). Forty rats were used to determine the predictive value of TOBEC estimates. With this instrument, TOBEC tended to underestimate FFM by an average of 3.9% and TBW by 5.3%. Accuracy was questionable for animals smaller than 13 g and TOBEC did not provide useful estimates of total body fat. Subject to these limitations, TOBEC instruments should prove to be useful for sequential in vivo estimations of body composition during growth and development of small animals.     

Morphometry of human ovaries in normal and growth-restricted fetuses

According to the fetal origins hypothesis, normal growth and development of abdominal organs is disturbed by intra-uterine growth restriction, leading to diseases later in life. The aims of this study were to investigate the effect of growth restriction on the ovaries of human fetuses and to investigate the dynamics of follicular growth in normal fetuses. We selected 21 normal female fetuses (controls) and seven severely intra-uterine growth-restricted female fetuses (IUGR cases) from all autopsy records over a 10-year period. Ovarian volume was calculated and from histological sections the volume-percentage of follicles in the ovarian cortex, the maximum diameters of individual follicles and the distribution of the follicle classes and oogonia were determined. The volume of the ovaries increased significantly from 0.10 to 0.36 cm³ in the second half of gestation. The mean volume-percentage of ovarian follicles and the mean follicle diameter significantly increased with 0.48% and 0.52 μm per week, respectively. Class B/C (intermediary) follicles (72%) were predominantly present. Class B (primordial) follicles decreased from over 20% to less than 10% and class C (primary) increased from 6 to 19%. Class A (oogonia) were frequently present before 30 gestational weeks, but were rare after that age. For all studied parameters we did not find differences between IUGR cases and controls. Intra-uterine growth restriction does not seem to disturb ovarian development in the human fetus. In the second half of gestation the follicle pool increases by the growth of individual follicles, the transition of follicle to larger classes, and probably by increasing follicle numbers. As most follicles at term were class B/C and C, follicles up to class C are probably part of the resting stock.     

Effects of mother's smoking on their infants' body composition as determined by total body potassium

It has been suggested that the lower birth weight of newborn infants of mothers who smoke is due mainly to a deficit of lean body mass (LBM). We tested this hypothesis by measuring total body potassium, thus deriving the LBM and fat mass, of newborn infants of mothers who smoked (I-SM; n = 32) or did not smoke (I-NSM; n = 46). Mothers who smoked were significantly younger than nonsmoking ones (25.4 and 28.9 yr, respectively) and with less years of education, but were similar in other parameters examined. The 78 infants, all singleton, were studied within 1 to 3 days of birth. The I-SM had significantly reduced birth weight, length, and head circumference but there was no difference in skinfold thickness. We measured total body potassium with a whole-body counter specially made for use with infants. Mean absolute total body potassium was significantly greater in the I-NSM, but the concentration in relation to weight was not different. Assuming 1 kg LBM to contain 52.1 mmol potassium, the mean LBM was 3028 g in the I-NSM and 2739 in the I-SM; mean fat mass was similar in both groups. Multiple regression analysis revealed an independent negative effect of mother's smoking on birth weight and LBM. This unequal reduction in LBM indicates a complex effect of smoking, probably mediated by alterations in protein synthesis and adipocyte metabolism. It may relate to the higher morbidity rates in infants of mothers who smoke.     

Placental weights of normal and aneuploid early human fetuses

Placental and body weights were plotted for 252 normal human fetuses less than 600 gm and mean regressions and 95% prediction intervals were calculated. Placentas from 62 aneuploid fetuses were compared to these standards. Placenta to body weight ratios from 34 trisomy-21 fetuses were not reduced but those from 15 trisomy-18 fetuses were generally decreased. One of 5 trisomy-13 ratios was below the prediction interval. Among 7 triploid fetuses the ratios were above the normal interval in 3 and below normal in 4. Three of the triploids that were below were associated with a karyotype of 69,XXX and did not have hydatidiform degeneration. All 4 placentas with hydatidiform changes were abnormally large. All of the 7 triploids had 3-4 syndactyly and 3 had hydrocephalus.     

Use of ultrasound and MRI for evaluation of lung volumes in fetuses with isolated left congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is an anomaly that results in lung hypoplasia and pulmonary hypertension. The lungs of the CDH fetus have an abnormal architecture, with fewer bronchial branches and decreased number of arteries and veins, factors which result in pulmonary compromise postnatally. The goal of this review is to evaluate prenatal prognostic factors in the fetus with isolated left CDH, with particular emphasis on fetal MRI. These imaging indicators may be used to provide health professionals and the parents with the most accurate information about fetal prognosis.     

Acute centralization of blood flow in compromised human fetuses evoked by uterine contractions

BACKGROUND: During fetal hypoxia blood is redistributed to the brain ('brain-sparing'). Sequential changes of the cerebral and placental circulation in parallel in comparisons between basal conditions and acute hypoxic stress have not yet been thoroughly studied in human fetuses. AIM: To explore acute fetal middle cerebral artery (MCA) circulatory changes relative to umbilical artery (UA) blood flow in a clinical experimental model with hypoxic stress provoked by uterine contractions during an oxytocin challenge test (OCT). STUDY DESIGN: Prospective comparative between imminently compromised (OCT positive) and un-compromised (OCT negative) fetuses. SUBJECTS AND METHODS: 82 term pregnancies suspected of intrauterine growth restriction were exposed to simultaneous electronic fetal heart rate monitoring and Doppler recordings of pulsatility index (PI) in the UA and MCA during basal conditions and during uterine contractions and relaxations at an OCT. OUTCOME MEASURES: Sequential changes of UA and MCA PI, OCT positive vs. negative cases. Nonparametric statistics with a P < 0.05 considered significant. RESULTS: The UA PI was significantly higher in OCT positive cases (N = 10) compared with OCT negative cases (N = 72) during uterine contractions and relaxations, but not during basal measurements. During contractions and relaxations the MCA PI decreased significantly in both groups (brain-sparing), but significantly more in OCT positive cases. CONCLUSIONS: During acute hypoxic stress, changes towards a centralization of blood flow to the brain develop in imminently compromised (OCT positive) fetuses at an expense of the umbilicoplacental blood flow, and the brain-sparing flow is more pronounced than in un-compromised (OCT negative) fetuses.     

MRI of the olfactory bulbs and sulci in human fetuses

Background: There is limited knowledge of the MRI pattern of the development of fetal olfactory bulbs and sulci. Objective: To describe the MRI appearance of olfactory bulbs and sulci in normal in vivo fetuses according to gestational age. Materials and methods: Olfactory bulbs and sulci were retrospectively assessed on brain MRI examinations of 88 normal fetuses between 24 and 39 weeks gestational age. Two reference centres were involved in the study and both used routine protocols that included axial and coronal T2- and T1-weighted sequences at 1.5 T. The results were compared both with the commonly used neuropathological data in the literature and with personal neuropathological data. Pearson’s chi-squared test or Fisher’s exact test were performed. One case of olfactory agenesis associated with CHARGE syndrome was identified. Results: T2-weighted coronal sequences were the most sensitive for detecting olfactory bulbs and sulci. Olfactory sulci were significantly better detected from 30 weeks onwards (90.9–100%; P<0.001). MRI showed a posteroanterior development of these sulci. Olfactory bulbs were better detected from 30 to 34 weeks (80–90.9%; P<0.002). Comparison with neuropathological data confirmed the posteroanterior development of the sulci and showed an important delay in detection of the olfactory structures (bulbs and sulci). No difference was observed between the two centres involved. Conclusions: To date, fetal MRI can depict olfactory sulci from 30 weeks gestational age onwards and olfactory bulbs from 30 to 34 weeks gestational age. This preliminary reference standard is useful to assess the normality of the olfactory system and to diagnose olfactory agenesis.     

Paediatric CT reference doses based on weight and CT dosimetry phantom size: local experience using a 64-slice CT scanner

Background  

Previously published dose reference level (DRL) values may no longer be applicable due to technological advancement. New Australian legislation recommends that local DRLs (LDRLs) are established to monitor the performance and dose of CT examinations.     

The effect of maternal hyperglycemia on gross body movements in human fetuses at 32–34 weeks' gestation

This study demonstrated that fetal gross body movements were not significantly altered by fluctuations in maternal plasma glucose concentration. Fetuses moved episodically a relatively constant amount of time whether mother received water orally, 50 g of glucose orally or a 25 g bolus of glucose intravenously. In addition, depending on the length of the observational epoch, the incidence of fetal gross body movements differed. As the length of the observational period increased, the chance of finding no fetal gross body movements decreased and at intervals of 24 min duration, fetal gross body movements were absent in only 2% of 24 min periods examined, irrespective of whether they had received water orally, 50 g of glucose orally or 25 g of glucose intravenously. It is concluded that maternal carbohydrate intake was not an important determinant of fetal body movements in healthy fetuses at 32–34 weeks' gestation.     

Horseshoe lung: useful angiographic and bronchographic images using multidetector-row spiral CT in two infants

Horseshoe lung is a rare congenital pulmonary anomaly of childhood that can be accompanied with other anomalies. The diagnosis has historically been accomplished with invasive catheter angiography and bronchography rather than CT. Two infants with horseshoe lung were recently diagnosed with CT. We report the imaging findings in these two patients with emphasis on angiographic and bronchographic demonstration of key abnormalities of horseshoe lung using multidetector-row spiral CT.     

Muscle analysis by measurement of maximal isometric grip force: new reference data and clinical applications in pediatrics

Skeletal muscle development is one of the key features of childhood and adolescence. Determining maximal isometric grip force (MIGF) using a hand-held Jamar dynamometer is a simple method to quantify one aspect of muscle function. Presently available reference data present MIGF as a function of chronological age. However, muscle force is largely determined by body size, and many children undergoing muscle performance tests in the clinical setting suffer from growth retardation secondary to a chronic disorder. Reference data were established from simple regressions between age or log height and log MIGF in a population of 315 healthy children and adolescents aged 6 to 19 y (157 girls). These data were used to calculate age- or height-dependent SD scores (SDS) for MIGF in three pediatric patient groups. In renal graft recipients (n = 14), the age-dependent MIGF SDS was markedly decreased (-2.5 +/- 1.9; mean +/- SD). However, these patients had short stature (height SDS, -2.5 +/- 1.2), and the height-dependent MIGF SDS was close to normal (-0.4 +/- 1.5). Similarly, in cystic fibrosis patients (n = 13) age-dependent MIGF SDS was -1.6 +/- 1.6, but height-dependent MIGF SDS was -0.5 +/- 1.1. Children with epilepsy who were taking anticonvulsant therapy (n = 34) had normal stature, and consequently age- and height-dependent MIGF SDS were similar (0.4 +/- 1.0 and 0.4 +/- 0.8, respectively). In conclusion, MIGF determination provides information on an important aspect of physical development. Height should be taken into account to avoid misinterpretation.     

Estimation of lung volume in infants by echo planar imaging and total body plethysmography.

Echo planar imaging (an extremely fast method of magnetic resonance imaging) was used to measure lung volume in a group of nine infants, all of whom had had respiratory problems. The mean echo planar imaging estimate of total lung volume was 44 +/- 9 ml/kg. In each case the right lung was larger than the left (ratio 52.8:47.2%). The mean thoracic gas volume was 36 +/- 8 ml/kg. The entire sequence of images of the thorax (about 400) takes five minutes to complete, infants require no sedation, and there are no side effects.