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Introduction and objective: Population standards of intrauterine growth are necessary to evaluate if the newborn has grown well, if their nutritional conditions are appropriate and to identify groups at risk as those small for gestational age (SGA). Differences in the number of SGA newborns identified, depending on the standard applied, have been analyzed in this study. Material and methods: Cross-sectional study conducted in 4,486 Caucasian newborns (2,361 boys and 2,125 girls), born between 35 and 41 weeks. Weight and length valuation was performed following the standard methodology. Percentage of children under the 10th percentile for weight and length was calculated depending on the standard used (Olsen et al. 2010, Lubchenco et al. 1966, Delgado et al. 1996, Carrascosa et al. 2008), being diagnosed of SGA. Results: Weight and length were significantly higher in boys than in girls at all ages. 10th percentile values defined for every gestational age are globally similar among the different standards and our population, with the clear exception of Lubchenco curves whose 10th percentile values are even 300 g. lower for the newborns at the highest gestational ages. Lubchenco charts do not fit the pattern of intrauterine growth of our population and identify a smaller number of SGA. The percentage of SGA of our sample ranged between 1.7% and 14% in depending on the standard, sex and gestational age considered. Conclusion: The number of children classified as SGA is different according to each standard used. Lubchenco charts identify a smaller number of SGA than the others. The rest of curves show similar values and seem to be well adapted for our population. The correct identification of SGA will allow a better assessment of short and long-term risks of these newborns. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Growth is a complex phenomenon that has in pediatric age special relevancy because it constitutes a fundamental indicator of nutritional status. OBJECTIVE: To evaluate differences about weight analysis of infants aged 0-18 months depending on the population reference used. METHODS: This is a longitudinal weight and length study in a representative sample of 383 infants from Aragon since birth until 18 months of age. A descriptive analysis was realized and 'z-scores' were calculated from five growth curves. Finally there was calculated the percentage of children who were staying above or under 2DS for weight depending on the standard used. RESULTS: 50.1% were males and 49.9% women. Weight and length of the children were higher in girls than in boys in all the ages (p<0.01). Major differences between weight z-score averages from standards were at 6 months and later. The percentage of children on a weight<2 DS ranged between 0.5 and one 3.3% at 18 months of age depending on the standard. CONCLUSION: Global differences exist when weight is evaluated in the same sample of infants up to 18 months of age depending on different population standards, as well as in the number of children who stay out of the limits of the normality with each of them. [ABSTRACT FROM AUTHOR]

Aim: Maternal health and gestational control are crucial to improving the newborn's prognosis. This study analyses demographic and obstetric factors at the beginning of pregnancy related to neonatal health, assessing their impact on the risk of hospital admission and prematurity., Methods: Observational retrospective study conducted in Northeast Spain with data of 9560 newborns between February 2017 and February 2022. The following have been evaluated as risk factors for hospital admission: nulliparity, multiple gestation, fertilisation techniques, foreign maternal origin, maternal age, smoking and residential location, dividing the sample according to gestational age. Hypothesis testing and logistic regression were performed., Results: Nulliparity, fertilisation techniques and multiple gestation represent a risk factor for neonatal admission (OR 22.48, 4.04 and 3.34, respectively), especially in premature newborns <32 weeks of GA (OR: 30.71, 10.71 and 22.76, respectively). Foreign maternal origin also adds risk of admission, both in term newborns (OR 1.26; CI: 1.10-1.43) and in premature babies <32 weeks of GA (OR 1.61; CI: 1.09-2.38). Tobacco does not present a significant risk of neonatal admission. The multivariate analysis model confirms the influence of the following factors in all the studied groups: nulliparity, multiple gestation and foreign maternal origin., Conclusions: Nulliparity and multiple pregnancies are both main risk factors for neonatal admission and premature delivery. The use of fertilisation techniques and the foreign origin of the mother significantly associate increased risk of admission and neonatal prematurity. These findings underscore the need for a comprehensive approach to prenatal care to improve neonatal prognosis and promote long-term health in risk populations., (© 2024 The Author(s). Journal of Paediatrics and Child Health published by John Wiley & Sons Australia, Ltd on behalf of Paediatrics and Child Health Division (The Royal Australasian College of Physicians).)

Introduction and Objective: Neonatal hypoglycemia offers multiple controversies. The study aims to assess the main factors involved in the development of early hypoglycemia in term and late preterm infants, and the implication of different environmental circumstances., Methods: A prospective cohort study in infants born between 34 0/7 weeks and 36 6/7 weeks of gestation. Three capillary blood glucose determinations were performed during the eight first hours after birth., Sample Size: 207, 59 neonates developed hypoglycemia., Results: Prenatal risk factors include gestational diabetes with poor glycemic control, twin pregnancy and gestational age. The presence of meconium amniotic fluid and planned cesarean delivery are associated with a higher probability of hypoglycemia. After birth, skin to skin contact, breastfeeding, soft lightening, and normothermia are described as protective factors. The predictive model that combines the type of lightening, body temperature and the excess of bases level, correctly classifies 98% of the severe hypoglycemia cases, with a high Nagelkerke R 2 value (0.645) and specificity of 99.5%., Conclusions: Postnatal environmental factors seem to be directly related to early hypoglycemia development, so it is essential to support the maternal-child union and breastfeeding. Our results allow better identification of neonates who are not subsidiary to performing blood glucose determinations because they have little risk of developing it., (Copyright © 2022 Asociación Española de Pediatría. Published by Elsevier España, S.L.U. All rights reserved.)

Introduction and Objective: Neonatal hypoglycemia offers multiple controversies. The study aims to assess the main factors involved in the development of early hypoglycemia in term and late preterm infants, and the implication of different environmental circumstances., Methods: A prospective cohort study, in infants born between 34 0/7 weeks and 36 6/7 weeks of gestation. Three capillary blood glucose determinations were performed during the eight first hours after birth., Sample Size: 207; 59 neonates developed hypoglycemia., Results: Prenatal risk factors include gestational diabetes with poor glycemic control, twin pregnancy and gestational age. The presence of meconium amniotic fluid and planned cesarean delivery are associated with a higher probability of hypoglycemia. After birth, skin to skin contact, breastfeeding, soft lightening, and normothermia are described as protective factors. The predictive model that combines the type of lightening, body temperature and the excess of bases level, correctly classifies 98% of the severe hypoglycemia cases, with a high Nagelkerke R 2 value (0.645) and specificity of 99.5%., Conclusions: Postnatal environmental factors seem to be directly related to early hypoglycemia development, so it is essential to support the maternal-child union and breastfeeding. Our results allow better identification of neonates who are not subsidiary to performing blood glucose determinations because they have little risk of developing it., (Copyright © 2021. Publicado por Elsevier España, S.L.U.)

Introduction: Introduction and objective: neonatal hypoglycemia persistently offers multiple diagnostic controversies. This study aims to present the current situation regarding neonatal hypoglycaemia detection, and to gain insiht into the most widely used portable glucometers in neonatal units today. Methods: an online questionnaire was prepared and sent to the members of the Spanish Society of Neonatology; a total of 75 hospitals participated. Results: portable glucometers continue to be widely used in the neonatal population. More than 75 % of units perform neonatal hypoglycemia screening in specific clinical circumstances, and 13 % of units continue to perform protocolized screening on all newborns at neonatal units. The higher the level of care, the higher the percentage of hypoglycaemia detection by other tests (such as blood gas analysis): chi2, p = 0.019. Multiple models of portable glucometers are currently used, with differences according to level of care (chi2, p = 0.01). Nova Biomedical, Abbott, and Roche Diagnostics models are most commonly used. Conclusions: differences in the performance of neonatal hypoglycaemia screening are observed, so standardised procedures and limiting the neonatal population at risk are important to reduce variability in clinical practice, and to improve the quality of neonatal care.

Introduction: Although primary immune thrombocytopenia (ITP) is rare in childhood, it is the most frequent cause of thrombocytopenia. There have been attempts to establish risk factors to predict the progression of the disease in order to optimise its management, which has changed in recent years due to, among other reasons, specialised care., Material and Methods: A retrospective, observational and analytical study was conducted on patients diagnosed with ITP over a 3-year period in a Paediatric Haematology specialist clinic., Results: From the epidemiological, clinical and analytical point of view, the characteristics of this group are similar to others. Most of the patients (23/31, 74.2%) had ITP for less than 12 months, with there being no serious complications related to the disease or the treatment received. It was established that risk factors were related to being slowly evolving (lower event-free survival (EFS)) with no statistical significance, female gender, age over 10 years, leukopenia absence of initial severe thrombocytopenia, and non-specialised care. The absence of a history of infection was significantly related to a lower EFS., Conclusions: The epidemiological and analytical risk factors for a slowly evolving ITP are the same that described in the literature. Patients treated before the beginning of specialised care also had a lower EFS. These data seem to support the current recommendation that rare diseases should be managed in specialised units., (Copyright © 2019. Publicado por Elsevier España, S.L.U.)

Introduction: Background and objective: hemodynamically significant patent ductus arteriosus (HS-PDA) is associated with an increased risk of necrotizing enterocolitis (NEC) and worse enteral tolerance in preterm newborns (PN). An association has been demonstrated between brain natriuretic propeptide (proBNP) and HS-PDA. Our objective was to analyze the relationship between proBNP levels and enteral tolerance, NEC risk and weight gain in PN. Material and methods: a retrospective study was performed in neonates born before 32 weeks' gestation or with birth weight below 1500 grams, in whom proBNP determination and echocardiography were performed at 48 to 72 h of life. Results: 117 patients were included. 65.8% had a HS-PDA and 9.4% had an outcome of NEC. HS-PDA was associated with longer duration of parenteral nutrition (p < 0.001), a confirmed NEC (p = 0.006) and worse weight gain during admission (p < 0.001). ProBNP levels were associated to NEC (no NEC 12189.5 pg / mL, range 654-247986; NEC 41445 pg/mL, range 15275-166172, p < 0.001). No association was found with the rest of gastrointestinal outcomes. Multivariate logistic regression analysis showed a significant association of NEC with gestational age and proBNP above 22,400 pg/mL (OR 13,386, 95% CI 1,541-116,262, p = 0.019). Conclusions: proBNP could be an early marker of severe digestive pathology in PN. Increased proBNP levels could be associated with a significant increased risk of NEC in very immature newborns.

Introduction: Patent ductus arteriosus (PDA) is a prevalent condition in preterm infants, and may be related to increased morbidity and mortality in the most immature newborns. Recent studies have examined the usefulness of brain natriuretic propeptide (proBNP) in the diagnosis of this pathology. The aim of the study was to evaluate the diagnostic efficacy of proBNP as a marker of hemodynamic overload in PDA., Paients and Methods: A retrospective study was conducted on preterm infants less than 32 weeks of gestation and/or weight less than 1500 grams. Echocardiogram and determination of proBNP levels were performed on all patients. Comparison was made by subgroups according to the presence of PDA and their haemodynamic characteristics., Results: Of the 60 patients enrolled, 71.7% had PDA, of which 86% had haemodynamically significant patent ductus arteriosus (HS-PDA). All of them, but one, received medical treatment with ibuprofen or acetaminophen. Surgical closure was required in 29.7% of HS-PDA. Higher values of proBNP were found in patients with HS-PDA (33338±34494.47pg/mL; p=.000) compared with patients with closed or non-haemodynamically significant ductus arteriosus. Higher values were also found in patients who required surgical closure of PDA (30596.8±14910.9; p=.004). A greater decrease inproBNP levels was found in the group of patients which duct closure after pharmacological treatment (68±24.69% vs -12.22±99.4%; p=.030). ProBNP cutoff-level for HS-PDA was calculated by ROC curve and it was 9321.5pg/mL (Specificity: 100%, Sensitivity: 94.6%)., Conclusions: ProBNP levels are related to the presence or absence of haemodynamically significant patent ductus arteriosus; and its variations with treatment response. High values are also related to the need for surgical closure of PDA., (Copyright © 2015 Asociación Española de Pediatría. Publicado por Elsevier España, S.L.U. All rights reserved.)

Introduction: Numerous obstacles may prevent a premature or sick neonate receiving their mother's milk. In these cases, pediatric scientific societies recommend feeding with donor human milk. In this article, it is explained what a milk bank is, how it works, the donors' selection method, and the benefits. We also describe the current situation in Aragon (Spain) is also described., Material and Methods: A retrospective and descriptive study was conducted on the perinatal sample characteristics, as well as an analytical observational study, comparing two sample groups: pre- and post-human milk bank. Finally, differences in the post-bank stage between those patients fed with own-mother's or donor human milk were determined., Results: The study included a total of 234 patients: 104 females and 130 males. Two groups: pre and post-bank, with 152 and 82 patients, respectively, which had similar characteristics at birth; length and head circumference were significantly higher in the post-bank group and a lower rate of necrotizing enterocolitis was also found. No statistically significant differences were found in other variables between subgroups fed with own-mother's milk and donor human milk., Discussion: The establishment of the human milk donor bank has a beneficial effect, as it reduces neonatal morbidity in cases of necrotizing enterocolitis. Human milk feeding could be a protective factor against neonatal sepsis due to improve immunity., Conclusions: The incidence of necrotizing enterocolitis is lower after the establishment of the milk bank. Studies with more patients may demonstrate differences in other variables., (Copyright © 2014 Elsevier España, S.L.U. All rights reserved.)

Objective: To identify socio-cultural, obstetric and perinatal characteristics associated with complete breastfeeding (CBF) during the first 4 months of age, depending on maternal origin., Material and Methods: Socio-cultural, obstetric and perinatal aspects associated with breastfeeding depending on maternal origin were evaluated in a longitudinal study in a representative infant population from Aragon (n = 1452)., Results: The prevalence of CBF was higher in immigrant mothers than in those from Spain. CBF was maintained in 37.2% of mothers from Spain at 4 months, compared with 43% of immigrants (P=.039) (RR Spanish/immigrants=0.76; 95% CI: 0.58-0.99); at 6 months this occurred in 13.9% vs. 23.8%, respectively (P<.001) (RR Spanish/immigrants=0.52; 95% CI: 0.37-0.72). The factors associated with CBF at 4 months are different between both groups. Mothers born in Spain are older (P=.002), have higher academic level (P=.001), greater parity (P=.003), and a higher probability of vaginal delivery (P=.005); and their children have the highest anthropometric values at birth. However, in immigrant mothers, the maintenance of CBF was associated with a higher maternal body mass index and with working at home. In both groups, CBF remains more frequently in those mothers who do not smoke (P=.001)., Conclusions: The prevalence of CBF during the first months of life is higher in immigrant mothers than in those from Spain, and socio-cultural, obstetric and perinatal factors are different, depending on maternal origin., (Copyright © 2013 Asociación Española de Pediatría. Published by Elsevier Espana. All rights reserved.)

Objectives: To study the current prevalence of breastfeeding (BF) in Aragon (Spain) during the first 12 months of life, and analyse its demographic, perinatal and social influential factors., Material and Methods: Obstetric, perinatal and feeding aspects were evaluated in a longitudinal and observational study, in a representative cohort of infant population from Aragon born between March 2009 to March 2010, controlled until 12 months of age (N=1.602)., Results: Exclusive or predominant BF was more frequent than the rest of feeding modalities during the first 4 months of life. Maintenance prevalence of any BF modality was 82.5% at 1(st) month of age, 71.8% at 3(rd), 54.3% at 6(th), and 27.8% at 12 months of age. Maternal variables that were significantly associated with BF maintenance both at 1 and 6 months of age were: delivery modality (higher probability in case of vaginal delivery), academic level (higher probability if university studies), origin (higher probability in mothers from Africa), adiposity (higher probability of normal weight or overweight mothers compared with obese ones), and not to smoke during gestation., Conclusions: BF prevalence in Aragon (Spain) during the first 12 months of age is high and has increased compared with previous data. BF continues in more than half of infants at six months and in a quarter of infants at 12 months of age. Maternal factors that significantly influence BF initiation and maintenance are, delivery modality, academic level, origin (immigration), adiposity and smoking habit., (Copyright © 2013 Asociación Española de Pediatría. Published by Elsevier Espana. All rights reserved.)

Objective: To check whether secular changes exist in growth pattern of caucasic children from the North of Spain up to 2 years of age compared with 25-30 years ago population growth curves., Material and Methods: Longitudinal study of a representative cohort of caucasic infants born a term in Aragon (n=1.099). Standard deviation scores (z-scores) for weight, length and body mass index (BMI) have been calculated by two available 25-30 years ago population growth curves (Sobradillo et al. and Ferrández et al.)., Results: At all ages, weight, length and BMI mean z-scores significantly vary depending on the growth standard curve used (p≤0.001). At birth, weight z-score is -0.36 (95%CI:-0.42;-0.30) according to Sobradillo et al. and -0.26 (95%CI:-0.29;0.33) according to Ferrández et al. These differences decreased progressively becoming minimum at 2 years (mean weight z-score -0.08 and -0.05; respectively). At this age, length mean z-score is +0.54 (95%CI:0.48;0.61) according to Sobradillo et al. and +0.19 (95%CI:0.12;0.25) according to Ferrández et al. Mean BMI z-scores of our sample showed lower values than selected standards., Conclusions: Current birth weight of caucasic infants from Northern Spain is lower than in the previous generation. At 2 years of age there is a trend of increasing length, with a similar weight, resulting in lower BMI values., (Copyright AULA MEDICA EDICIONES 2013. Published by AULA MEDICA. All rights reserved.)

Introduction: Being born small for gestational age (SGA) has short and long term risks. The aim of this study was to describe perinatal and socio-cultural characteristics, and the pattern of growth and diet of SGA infants during their first 6 months of life., Materials and Methods: Anthropometry and diet were evaluated during six months in a representative sample of 1596 newborns the population of Aragon (Spain)., Results: Mothers of SGA (N=94) infants gained less weight during pregnancy (10.5±5.8 vs 12.0±5.07 kg, P=.012), gestational age at birth was lower (37.84±1.7 vs 39.06±1.6 weeks, P<.001), and the probability of cesarean delivery was higher (37.2% vs 20.5%, P=.001). The height of the mother was lower in the SGA group (1.61±0.58 vs 1.63±0.06 metres, P=.004), but their body mass index was similar. No differences were found between groups in social or cultural aspects. Mothers of SGA infants smoked more during pregnancy (32.3% vs 18.5%, P=.003) (RR = 1.92; 95% CI; 1.31 to 3.02). Infants born SGA remained smaller during the first 6 months of life, and the monthly weight gain was similar to the rest. In the SGA group, the prevalence of breastfeeding was lower at 4 months of age (54.9% vs 68.2%, RR = 0.58, 95% CI; 0.38 to 0.89)., Conclusions: Infants born SGA are more likely to converge a number of characteristics that must be considered together because they may lead to health risks. SGA do not show a rapid recovery pattern of postnatal growth, and their smaller size persists at six months., (Copyright © 2011 Asociación Española de Pediatría. Published by Elsevier España. All rights reserved.)

Introduction: One in every four women smoke at the beginning of the pregnancy in Spain; of these, 25-50% give up smoking during gestation and most of them smoke again after childbirth. Maternal smoking has harmful effects on babies, such as low birth-weight with its resulting morbidity. The objective of this study is to compare the anthropometric and socio-cultural characteristics between newborns from smoking motheŕs and those from non- smoking ones., Materials and Methods: Smoking habits and the socio-cultural characteristics were assessed from a sample of 1499 pregnant women, as well as their newborn anthropometric variables of their newborn babies during 2009 in the Aragon region of Spain., Results: In the sample of 1499 pregnant women the prevalence of smoking during pregnancy was 19.6%; among the Spanish women, 23% of them smoked during the gestation compared with only 11% in women from other countries. The smoker mothers were younger and they had a lower educational level than the non smoker ones; however, there were no statistical differences between their anthropometric characteristics. Newborns from smoker women in Aragon had a lower weigh at delivery (3155 vs. 3295 grams: p<.001) and a relative risk of low weight at birth for their gestational age of 2.1 (95% CI: 1.35 - 2.97). The length and the rest of newborn anthropometric variables were also affected., Conclusion: The prevalence of smoking during gestation is high in Aragon. The mothers who smoke are younger and have different socio-cultural characteristics compared with non-smoker mothers. Maternal smoking habits have a harmful effect on newborn nutritional status, representing an avoidable risk of low weight at birth., (Copyright © 2011 Asociación Española de Pediatría. Published by Elsevier Espana. All rights reserved.)

Introduction: Maternal nutritional status is an important factor of adequate intrauterine growth and neonatal weight. The aim of this study is to evaluate the relationship between pre-gestational BMI (Body Mass Index) and breastfeeding duration, as well as infant anthropometric measurements during their first six months of life., Materials and Methods: Anthropometric measurements and the type of feeding were evaluated in a representative sample of 1,547 newborns from our population during 2009, according to their maternal BMI, and also in a sub-cohort of 759 infants followed up to 6 months of life., Results: A total of 72.9% of women had a normal weight, 18.7% were overweight and 8.4% obese. Women with a BMI ≥ 25 kg/m(2) had lower weight gain during pregnancy (P < .001), lower socioeconomic and cultural level (P < .001), and their infants had higher weight at delivery (P=.003) and at 6 months of life, with no differences in body length. Newborn weight increased in relation to maternal BMI, but over 35 kg/m(2) it decreased progressively (P < .001). Breastfeeding prevalence in obese women was 58.5% at hospital postpartum discharge, and 8.6% at six months of life; as opposed to 70.8% and 13.9%, respectively in women with normal BMI., Conclusions: In our sample, maternal obesity is associated with a low socioeconomic and cultural level, higher infant weight at delivery and at 6 months of life, and less prevalence of exclusive breastfeeding; all of them nutritional risk factors in the short and long term., (Copyright © 2010 Asociación Española de Pediatría. Published by Elsevier Espana. All rights reserved.)

Objective: Our objective was to study the correlations between weight and length and weight index and brachial areas in healthy term newborns as indicators of nutritional status., Patients and Methods: We studied 794 consecutive Caucasian newborns, 377 male and 417 females, with gestational ages of 39 +/- 09 weeks and adequate weights. We measured weight, length, weight/length index, body mass index and weight index. Measurements of the arm perimeter and tricipital skinfold were used to calculate the fatty, lean and total areas by two different methods. Mean, standard deviation and percentiles were utilized in the measurements. The Student's t-test was used to calculate differences and Pearson's test for correlations., Results: We found that weight, length and weight/length indexes were higher in males than in females, except for the weight index. Brachial areas and parameter were higher in females, except for the lean area. We did not find significant differences between gender in brachial measurements calculated by the different methods. Among the males, we found a high degree of correlation between weight and the weight/length index (r = 0.963; p < 0.0001), and weight and total body area (r = 0.649; p < 0.0001). Similar data were obtained among females, where in addition a high correlation was found between the fat percentage and the body mass index (BMI, r = 0.223; p < 0.0001), as well as between brachial areas and BMI in both genders (p < 0.0001)., Conclusions: In normal newborns, the brachial areas, taken as indicators of body composition, are statistically significantly correlated with the anthropometric parameters widely used to measure the nutritional status of newborns.

Objective: We performed an anthropometric study in a series of normal full-term newborns to evaluate the discriminatory capabilities of the submandibular skinfold compared to other anthropometric parameters., Material and Methods: We studied 794 consecutive Caucasian newborns, 377 males and 471 females, with a mean gestational age of 39.5 +/- 0.9 weeks and adequate weights for age. Anthropometric variables analyzed included weight, length, left arm circumference and bicipital, tricipital, subscapular, suprailiac and submandibular skinfolds. Statistical analysis was performed by using the Student's t-test to evaluate differences between the different parameters and by Pearson's test to look for correlations among them., Results: The weight and lengths of male newborns were significantly higher than those of female newborns (p < 0.005) These parameters showed differences with other series of newborns studied. Measurements of the tricipital, subscapular and suprailiac skinfolds were significantly different between males and females (p < 0.005); however, bicipital and submandibular skinfolds were not. The submandibular skinfold measurement highly correlated with the other skinfold measurements, especially with the bicipital measurement, in both males (0.536; p < 0.0001) and females (0.578; p < 0.001). Submandibular skinfold measurements also correlated with weight and arm circumference in both sexes., Conclusions: Some somatometric measurements in normal term newborns differ significantly between the sexes, especially weight, length and tricipital, subscapular and suprailiac skinfolds. The submandibular skinfold correlates well with weight, arm circumference and the four routinely measured skinfolds. This finding suggests that measurement of the submandibular skinfold should be included in the evaluation of the newborn's nutritional status.

We have registered, on 36 normal newborns at term, ECG recordings of sixty seconds at a speed of 100 mm/second, from birth tooth sixth month of postnatal life. The heart rate variability was measured on its double slope, short and long term by the numerical method that Yeh proposed, consistent with the "differential index" (DI) and the "interval index" (II). For the short term variability, we have obtained minimum values at birth and maximum values at 72 hours of postnatal life, with a tendency to drop up to the end of the first month and later to become stable until the end of six months of age. The changes found among different ages, could be related to modifications in basal heart rate under autonomic nervous system control. The variability values of the long term, do not show a clear age relation.