Foot length--a new and potentially useful measurement in the neonate

Timing of organogenesis underscores the evolution of neonatal life histories and powered flight in bats

Bats have undergone one of the most drastic limb innovations in vertebrate history, associated with the evolution of powered flight. Knowledge of the genetic basis of limb organogenesis in bats has increased but little has been documented regarding the differences between limb organogenesis in bats and that of other vertebrates. We conducted embryological comparisons of the timelines of limb organogenesis in 24 bat species and 72 non-bat amniotes. In bats, the time invested for forelimb organogenesis has been considerably extended and the appearance timing of the forelimb ridge has been significantly accelerated, whereas the timing of the finger and first appearance of the claw development has been delayed, facilitating the enlargement of the manus. Furthermore, we discovered that bats initiate the development of their hindlimbs earlier than their forelimbs compared with other placentals. Bat neonates are known to be able to cling continuously with their well-developed foot to the maternal bodies or habitat substrates soon after birth. We suggest that this unique life history of neonates, which possibly coevolved with powered flight, has driven the accelerated development of the hindlimb and precocious foot.

Diagnostic accuracy of neonatal foot length to identify preterm and low birthweight infants: a systematic review and meta-analysis

Introduction

Eighty percent of neonatal deaths occur among babies born preterm and/or small for gestational age (SGA). In sub-Saharan Africa and South Asia, approximately 40% of births occur outside of health facilities, and gestational age (GA) and birth weight are commonly unknown. Foot length (FL) has been proposed as a simple, surrogate measurement to identify and triage small babies born in the community. We conducted a systematic review and meta-analysis of the diagnostic accuracy of newborn FL to classify preterm and low birthweight infants.

Methods

PubMed, EMBASE, Cochrane, Web of Science, POPLINE and WHO Global Health Library databases were searched. Studies of live-born infants that compared FL with GA and/or birth weight were included. Data on diagnostic accuracy were summarised, described, and pooled, as appropriate.

Results

Six hundred and two studies were identified and 41 included. Techniques for measuring FL included use of a firm plastic ruler, callipers, footprint or a measuring board. Twelve studies assessed the diagnostic accuracy of FL to identify preterm births; however, data were not pooled given heterogeneity and low quality of GA. 19 studies used FL to identify low birthweight infants (<2500 g, <2000 g). Among studies in Asia (n=3), FL <7.7 cm had pooled sensitivity and specificity of 87.6% (95% CI 61.1% to 99.0%) and 70.9% (95% CI 23.5% to 95.1%), respectively, to identify <2500 g infants. FL <7.3 cm had 82.1% (95% CI 63.7% to 92.2%) sensitivity and 82.1% (95% CI 59.2% to 90.8%) specificity for identifying <2000 g infants (n=3). In the African studies (n=3), FL <7.9 cm had pooled sensitivity and specificity of 92.0% (95% CI 85.6% to 95.7%) and 71.9% (95% CI 44.5% to 89.1%), respectively, to identify <2500 g neonates.

Conclusions

FL is a simple proxy measure that can identify babies of low birthweight with high sensitivity, though somewhat lower specificity. Additional research is needed to determine the validity of FL to identify preterm infants, and understand the programmatic impact of screening on healthcare seeking and outcomes.

PROSPERO registration number

CRD42015020499

Anthropometric measures that identify premature and low birth weight newborns in Ethiopia: a cross-sectional study with community follow-up

OBJECTIVE

To investigate foot length (FL), chest circumference (CHC) and mid-upper arm circumference (MUAC) as predictors of low birth weight (LBW) or prematurity, and to describe the agreement between the gestational age (GA) assessments ascertained by the New Ballard Score (NBS) and the Eregie model.

METHODS

A hospital-based cross-sectional study with community follow-up in a subset was conducted in Jimma University Medical Center, Ethiopia. GA (NBS and Eregie model), weight, FL, CHC and MUAC were measured at birth. Anthropometrics were repeated at 5 days of age.

RESULTS

The optimal cut-offs indicative of LBW were ≤7.7 cm for FL; ≤31.2 cm for CHC and ≤9.8 cm for MUAC. CHC, MUAC and FL identified LBW with sensitivities (95% CI) of 91.6 (86.9 to 95), 83.7 (77.8 to 88.5) and 84.2 (78.4 to 88.9), and specificities (95% CI) of 85.4 (83.3 to 87.4), 90.2 (88.4 to 91.9) and 73.9 (71.3 to 76.4), respectively. CHC, MUAC and FL identified prematurity with sensitivities of 83.8 (76.7 to 89.4), 83.1 (75.9 to 88.9) and 81.7 (74.3 to 87.7), and specificities of 81.1 (78.9 to 83.3), 63.4 (60.7 to 66.1) and 77.0 (74.6 to 79.3), respectively. The cut-offs identified have comparable diagnostic ability for LBW and prematurity when measurements are repeated on day 5 of age. The GA assessment by the NBS and the Eregie model gave similar results, with the mean difference of 1.2 weeks.

CONCLUSION

CHC, MUAC and FL taken on day 1 and 5 after birth could be used as diagnostic tools for LBW or prematurity. The Eregie model for GA estimation gives similar results to the NBS.

Skin-interfaced biosensors for advanced wireless physiological monitoring in neonatal and pediatric intensive-care units

Standard of care management in neonatal and pediatric intensive care units (NICUs and PICUs) involve continuous monitoring of vital signs with hard-wired devices that adhere to the skin and, in certain instances, include catheter-loaded pressure sensors that insert into the arteries. These protocols involve risks for complications and impediments to clinical care and skin-to-skin contact between parent and child. Here we present a wireless, non-invasive technology that not only offers measurement equivalency to these management standards but also supports a range of important additional features (without limitations or shortcomings of existing approaches), supported by data from pilot clinical studies in the neonatal intensive care unit (NICU) and pediatric ICU (PICU). The combined capabilities of these platforms extend beyond clinical quality measurements of vital signs (heart rate, respiration rate, temperature and blood oxygenation) to include novel modalities for (1) tracking movements and changes in body orientation, (2) quantifying the physiological benefits of skin-to-skin care (e.g. Kangaroo care) for neonates, (3) capturing acoustic signatures of cardiac activity by directly measuring mechanical vibrations generated through the skin on the chest, (4) recording vocal biomarkers associated with tonality and temporal characteristics of crying impervious to confounding ambient noise, and (5) monitoring a reliable surrogate for systolic blood pressure. The results have potential to significantly enhance the quality of neonatal and pediatric critical care.

Action-oriented colour-coded foot length calliper for primary healthcare workers as a proxy for birth weight & gestational period

Background & objectives:

Foot length of the newborn has a good correlation with the birth weight and is recommended to be used as a proxy measure. There can be variations in the measurement of foot length. A study was, therefore, carried out to develop a foot length calliper for accurate foot length measurement and to find cut-off values for birth weight and gestational age groups to be used by primary healthcare workers.

Methods:

This study was undertaken on 645 apparently healthy newborn infants with known gestational age. Nude birth weight was taken within 24 h of birth on a standard electronic weighing machine. A foot length calliper was developed. Correlation between foot length and birth weight as well as gestational age was calculated. Correctness of cut-off values was tested using another set of 133 observations on the apparently healthy newborns. Action-oriented colour coding was done to make it easy for primary healthcare workers to use it.

Results:

There was a significant correlation of foot length with birth weight (r=0.75) and gestational age (r=0.63). Cut-off values for birth weight groups were 6.1, 6.8 and 7.3 cm and for gestational age of 6.1, 6.8 and 7.0 cm. Correctness of these cut-off values ranged between 77.1 and 95.7 per cent for birth weight and 60-93.3 per cent for gestational age. Considering 2.5 kg as cut-off between normal birth weight and low birth weight (LBW), cut-off values of 6.1, 6.8 and 7.3 were chosen. Action-oriented colour coding was done by superimposing the colours on the scale of the calliper, green indicating home care, yellow indicating supervised home care, orange indicating care at newborn care units at primary health centres and red indicating Neonatal Intensive Care Unit care for infants.

Interpretation & conclusions:

A simple device was developed so that the primary health care workers and trained Accredited Social Health Activist workers can identify the risk of LBW in the absence of accurate weighing facilities and decide on the type of care needed by the newborn and take action accordingly.

Foot length measurements of newborns of high and low risk pregnancies

OBJECTIVE

Comparing foot length measurements of newborns in high and low risk pregnancies at a public hospital in Goiânia, GO, Brazil.

METHOD

A cross-sectional study carried out between April, 2013 and May, 2015, with a sample consisting of 180 newborns; 106 infants of women from high-risk pregnancies and 74 of women from low-risk pregnancies. Data were descriptively analyzed. Foot length measurement was performed using a stiff transparent plastic ruler, graduated in millimeters. The length of both feet was measured from the tip of the hallux (big toe) to the end of the heel.

RESULTS

A statistically significant relationship was found between the foot length and newborn's weight, between the cephalic and thoracic perimeters in the high-risk group and between the cephalic perimeter in the control group.

CONCLUSION

There is a need for creating cut-off points to identify newborns with intrauterine growth disorders using foot length.

OBJETIVO

Comparar as medidas do comprimento hálux-calcâneo de recém-nascidos em gestações de alto e baixo risco em um hospital público de Goiânia, GO.

MÉTODO

Estudo transversal, realizado no período de abril de 2013 a maio de 2015, cuja amostra constituiu-se de 180 recém-nascidos, 106 filhos de mulheres com gestação de alto risco e 74 de mulheres com gestação de baixo risco. Os dados foram analisados descritivamente. A medida do comprimento hálux-calcâneo foi realizada utilizando-se de régua plástica transparente rígida, graduada em milímetros. Foram medidos ambos os pés, aferindo-se o comprimento da ponta do hálux até a extremidade do calcâneo.

RESULTADOS

Foi encontrada relação estatisticamente significante entre o comprimento hálux-calcâneo e o peso do recém-nascido, entre os perímetros cefálico e torácico no grupo de alto risco e entre o perímetro cefálico no grupo controle.

CONCLUSÃO

Existe necessidade da criação de pontos de corte para identificar recém-nascidos com desvios de crescimento intrauterino utilizando-se do comprimento hálux-calcâneo.

OBJETIVO

Comparar las mediciones de la longitud hallux-calcáneo de los recién nacidos en embarazos de alto y bajo riesgo en un hospital público de Goiânia, GO.MÉTODOSEstudio transversal realizado de abril 2013 a mayo 2015, cuya muestra estuvo constituida por 180 recién nacidos, 106 de mujeres con embarazos de alto riesgo y 74 de mujeres con embarazos de bajo riesgo. Los datos se analizaron de manera descriptiva. La medida de la longitud hallux-calcáneo se realizó mediante regla de plástico rígido transparente, graduada en milímetros. Se midieron en ambos pies, las longitudes de la punta del hallux hasta el final del calcáneo.

RESULTADOS

Se encontró una relación estadísticamente significativa entre la longitud hallux-calcáneo y el peso del recién nacido, entre las circunferencias cefálica y torácica en el grupo de alto riesgo y entre la circunferencia cefálica en el grupo control.

CONCLUSIÓN

Existe la necesidad de crear puntos de corte para identificar los recién nacidos con desviaciones de crecimiento intrauterino utilizando la longitud desde el hallux hasta el calcáneo.

Postnatal Foot Length to Determine Gestational Age: A Pilot Study

Gestational age is a critical factor in the management, decision-making, prognostication and follow-up of newborn infants. It is also essential for research and epidemiology. In the absence of an early assessment of fetal gestation by abdominal ultrasound, many neonatal units in developing countries determine gestational age by neonatal scores and last menstrual period-both of which are highly inaccurate. The aim of this pilot study was to determine whether postnatal foot length measurement could accurately determine gestational age in a specified South African hospitalized neonatal population. Foot length was measured with a plastic Verniere's caliper. Foot length was shown to correlate well with gestational age (r = 0.919,p < 0.001). Intra-observer and inter-observer variability of foot length measurements was low. Foot length can therefore be used with high accuracy to determine the gestational age in a population where there is poor access to or utilization of antenatal sonar.

Foot Length, Chest Circumference, and Mid Upper Arm Circumference Are Good Predictors of Low Birth Weight and Prematurity in Ethnic Minority Newborns in Vietnam: A Hospital-Based Observational Study

Background

The evaluation of tools to accurately identify low birth weight (LBW) and/or premature newborns in resource-limited countries is a research priority. We explored the use of foot length, chest circumference, and mid-upper arm circumference (MUAC) measured within 24 h as diagnostic tools for identifying newborns who are LBW, premature, or both; and compared measurements taken at birth with those taken at five days of age.

Materials and Methods

An observational study was undertaken in Hoa Binh Province General Hospital, Vietnam, in ethnic minority newborns. Birth weight, foot length, chest circumference, and MUAC were measured within 24 h of birth and in a subset of 200, were repeated on day five of life. Gestational age was estimated using the New Ballard Score. Receiver Operating Characteristic curves and optimal cut-points (the point with the highest sensitivity and specificity where the sensitivity was at least 0.8) were calculated, for predicting prematurity, LBW, and both. Measurements within 24 h and at five days of life were compared.

Results

485 newborns were recruited. Chest circumference and MUAC measured within 24 h of birth were found to be highly predictive of LBW (both yielding area under the curve [AUC] of 0.98, 95% confidence interval [CI] 0.96–0.99), and performed marginally better than foot length (AUC 0.94, 95%CI 0.92–0.96). The optimal cut-points for measurements within 24 h of birth were ≤7.4cm for foot length; ≤30.4cm for chest circumference; and ≤ 9.0cm for MUAC. There was statistical evidence that anthropometric measurements taken within 24 h of birth were higher than measurements on day five (p<0.02 for all anthropometric measurements) but the magnitude of these differences was small (at most 2mm).

Conclusions

All measurements taken within 24 h of birth were good predictors of LBW, prematurity and both. Differences in measurements taken within 24 h and on day five were not clinically relevant. Further research will ensure that the application of these measures is reliable in community settings.

The reliability of a newborn foot length measurement tool used by community volunteers to identify low birth weight or premature babies born at home in southern Tanzania

Background

Low birthweight babies need extra care, and families need to know whether their newborn is low birthweight in settings where many births are at home and weighing scales are largely absent. In the context of a trial to improve newborn health in southern Tanzania, a counselling card was developed that incorporated a newborn foot length measurement tool to screen newborns for low birth weight and prematurity. This was used by community volunteers at home visits and shows a scale picture of a newborn foot with markers for a ‘short foot’ (<8 cm). The tool built on previous hospital based research that found newborn foot length <8 cm to have sensitivity and specificity to identify low birthweight (<2500 g) of 87% and 60% respectively.

Methods

Reliability of the tool used by community volunteers to identify newborns with short feet was tested. Between July-December 2010 a researcher accompanied volunteers to the homes of babies younger than seven days and conducted paired measures of newborn foot length using the counselling card tool and using a plastic ruler. Intra-method reliability of foot length measures was assessed using kappa scores, and differences between measurers were analysed using Bland and Altman plots.

Results

142 paired measures were conducted. The kappa statistic for the foot length tool to classify newborns as having small feet indicated that it was moderately reliable when applied by volunteers, with a kappa score of 0.53 (95% confidence interval 0.40 – 0.66) . Examination of differences revealed that community volunteers systematically underestimated the length of newborn feet compared to the researcher (mean difference −0.26 cm (95% confidence interval −0.31—0.22), thus overestimating the number of newborns needing extra care.

Conclusions

The newborn foot length tool used by community volunteers to identify small babies born at home was moderately reliable in southern Tanzania where a large number of births occur at home and scales are not available. Newborn foot length is not the best anthropometric proxy for birthweight but was simple to implement at home in the first days of life when the risk of newborn death is highest.

A novel technique for infant length measurement based on stereoscopic vision

BACKGROUND

Monitoring infant growth is essential for evaluation of development and is an important indicator of health and illness. Length is an essential indicator of infant growth, however, length measurement methods suffer from limitations which restrict their use.

OBJECTIVE

To improve infant length measurement by development of a novel, accurate, precise and practical measurement technique.

METHODS

A new system based on stereoscopic vision was developed. The system is comprised of two digital still cameras combined with software that calculates the infant's length from two simultaneously taken pictures. Length measurements of 54 healthy newborns were performed using a standard length board and the stereoscopic system. The two measurement methods were compared.

RESULTS

Mean infant length was 473.1 (SD=29.1) mm versus 473.3 (SD=29.3) mm by length board and by the stereoscopic system, respectively. The mean difference between measurements was 0.2 (SD=2.5) mm and the mean of the absolute values of differences was 2.0 (SD=1.4) mm. Bland-Altman analysis showed good agreement between the two measurement methods. Precision of the new technique was demonstrated by a technical error of measurement of 2.57 mm.

CONCLUSIONS

The stereoscopic system is accurate, reliable, easy to use, and involves less handling and discomfort to the newborns. It has the potential to measure premature infants or sick neonates through incubators.

Measuring new born foot length to identify small babies in need of extra care: a cross-sectional hospital based study

OBJECTIVE

The neonatal mortality rate (NMR) continues to remain quite high, one important cause being preterm deliveries. The main obstacle in the pathway towards decreasing NMR is identification of babies in need of extra care. To analyze the utility of newborn foot length as a proxy measure for birth weight and gestational age.

METHODS

A cross-sectional study done in a hospital of eastern India with 351 babies during 4 months. Right foot length of each recorded using a plastic, stiff ruler.

FINDINGS

48.1% babies were preterm, 51.8% low birth weight (LBW) and 33.3% very low birth weight (VLBW). Foot length less than 7.75 cm has 92.3% sensitivity and 86.3% specificity for identification of preterm neonates. For identification of LBW babies (<2500 gm) a foot length less than 7.85cm has 100% sensitivity and 95.3% specificity. Foot length less than 6.85 cm has 100% sensitivity and 94.9% specifity for identification of VLBW babies (<1500 gm).

CONCLUSION

Foot length may be used in the identification of LBW and preterm babies who are in need of extra care.

A novel approach toward noninvasive monitoring of transcutaneous CO(2)

The continuous monitoring of transcutaneous gases is an integral part of neonatal intensive care. Present monitors measure the equilibrating values of these gases by raising the skin temperature to 42°C or above. Because neonatal skin is very sensitive and delicate, this often leads to serious skin injuries. In this work, we present a new approach to the noninvasive measurement of transcutaneous partial pressure of carbon dioxide (tcpCO2) based on the initial pseudo steady state diffusion rates instead of the mass-transfer equilibrium. Because we are following initial diffusion rates, each measurement takes no more than a few minutes. Additionally, raising the surface temperature is not required, thus, skin irritation and burns are highly unlikely. A dual-chamber diffusion vessel with either porcine skin or dialysis membrane placed between the two chambers was used to mimic neonatal skin. LI-820 CO2 Analyzer was used to measure the CO2 diffusing through the membrane or skin. Initial experiments on adult human skin under varying physical activities, food intake and breathing patterns showed a strong influence of the various conditions on the amount of CO2 diffusing through skin. These initial findings suggest that this method can be used not only on neonates but to a wider population of patients.

Identifying high-risk babies born in the community using foot length measurement at birth in Uganda

BACKGROUND

Low birthweight and prematurity are risk factors for neonatal mortality. Identifying low birthweight and premature babies at birth and giving them appropriate care could increase their chances of survival. This study aimed at assessing the use of foot length as a surrogate for low birthweight and prematurity, and recommending an operational cut-off for identifying high-risk babies at the community level in low resource settings.

METHODS

  A hospital-based cross-sectional study was carried out between 1 September and 17 December 2009 in Uganda. Foot length of 711 newborns was measured using three different methods and their weight taken using a digital salter scale within 24 h of life. Gestational age of the newborns was also estimated using the Eregie method. Non-parametric receiver operating characteristic curve analysis was carried out to determine the foot length method with the highest predictive value to predict low birthweight and premature newborns. Sensitivity, specificity and predictive values for a range of foot lengths were estimated to determine the optimal cut-off to predict low birthweight and prematurity in this setting.

RESULTS

  Of the 711 babies recruited on day 1, 85 (12%) babies were low birthweight (<2500 g) and 29 (4%) premature (<37 weeks). The operational cut-off for foot length to detect small babies was defined as 7.6 cm, with sensitivity 85% [95% confidence interval (CI) 75-92] and specificity 81% (95% CI 78-84) for low birthweight, and sensitivity 96% (95% CI 82-100) and specificity 76% (95% CI 73-79) for premature babies.

CONCLUSION

  Foot length in the first days of life can predict low birthweight and prematurity among newborn babies in this setting. Further evaluation is needed to assess the feasibility of its use by community health workers to identify babies that need extra care.

Measuring newborn foot length to identify small babies in need of extra care: a cross sectional hospital based study with community follow-up in Tanzania

Background

Neonatal mortality because of low birth weight or prematurity remains high in many developing country settings. This research aimed to estimate the sensitivity and specificity, and the positive and negative predictive values of newborn foot length to identify babies who are low birth weight or premature and in need of extra care in a rural African setting.

Methods

A cross-sectional study of newborn babies in hospital, with community follow-up on the fifth day of life, was carried out between 13 July and 16 October 2009 in southern Tanzania. Foot length, birth weight and gestational age were estimated on the first day and foot length remeasured on the fifth day of life.

Results

In hospital 529 babies were recruited and measured within 24 hours of birth, 183 of whom were also followed-up at home on the fifth day. Day one foot length <7 cm at birth was 75% sensitive (95%CI 36-100) and 99% specific (95%CI 97-99) to identify very small babies (birth weight <1500 grams); foot length <8 cm had sensitivity and specificity of 87% (95%CI 79-94) and 60% (95%CI 55-64) to identify those with low birth weight (<2500 grams), and 93% (95%CI 82-99) and 58% (95%CI 53-62) to identify those born premature (<37 weeks). Mean foot length on the first day was 7.8 cm (standard deviation 0.47); the mean difference between first and fifth day foot lengths was 0.1 cm (standard deviation 0.3): foot length measured on or before the fifth day of life identified more than three-quarters of babies who were born low birth weight.

Conclusion

Measurement of newborn foot length for home births in resource poor settings has the potential to be used by birth attendants, community volunteers or parents as a screening tool to identify low birth weight or premature newborns in order that they can receive targeted interventions for improved survival

Assessment of growth from foot length in Taiwanese neonates

BACKGROUND

Previous studies have demonstrated a positive correlation between foot length (FL) and birth body weight (BBW), birth body length (BBL), and head circumference (HC). However, there is no data on birth FL in Taiwan. The aim of this study was to evaluate FL measurement in Taiwanese neonates as a method of estimating other anthropometric indices.

METHODS

In this retrospective study, we enrolled 256 babies born at our hospital and Kaohsiung Veterans General Hospital from 2003-2005. Medical records were reviewed for sex, BBW, BBL, HC, gestational age, and birth FL. Ill newborns, small-for-gestational-age babies, or those with poor birth footprints were excluded. FL at birth was measured from the center of the back of the heel to the tip of the big toe. Linear regression analysis was used to investigate the relation of FL to BBW and BBL. The intraclass correlation coefficient was used to assess inter-rater reliability.

RESULTS

A total of 256 babies were reviewed. There were 136 male and 120 female neonates. The gestational age was 38.5+/-1.3 (mean+/-standard deviation) weeks, ranging from 35-42 weeks. The BBW was 3137+/-396g. The BBL was 51.1+/-2.1 cm. The HC was 33.5+/-1.7 cm. The FL was 7.4+/-0.46 cm. The regression equation for BBW (y) on FL (x) was as follows: y=486.2+360.4x (p<0.001, r=0.421). The regression equation for BBL (y) on FL (x) was as follows: y=40.1+1.45x (p<0.001, r= 0.305). The regression equation for HC (y) on FL (x) was as follows: y=14.8+2.53x (p<0.001, r=0.423). FL showed excellent reliability, with an intraclass correlation coefficient of 0.965 (p<0.001).

CONCLUSION

Our study demonstrated a significant degree of correlation between FL and BBW, BBL and HC. However, it did not reliably estimate BBW, BBL, or HC-the three anthropometric indices were weakly correlated (r<0.5) with FL.

Relationship between the surrogate anthropometric measures, foot length and chest circumference and birth weight among newborns of Sarlahi, Nepal

BACKGROUND

Classification of infants into low birth weight (LBW, <2500 g) or very low birth weight (VLBW, <2000 g) categories is a crucial step in targeting interventions to high-risk infants.

OBJECTIVE

To compare the validity of chest circumference and foot length as surrogate anthropometric measures for the identification of LBW and VLBW infants.

SUBJECTS AND SETTING

Newborn infants (n=1640) born between March and June 2004 in 30 Village Development Committees of Sarlahi district, Nepal.

DESIGN

Chest circumference, foot length and weight (SECA 727, precise to 2 g) of newborns were measured within 72 h after birth. The sensitivity, specificity and predictive values for a range of cutoff points of the anthropometric measures were estimated using the digital scale measurements as the gold standard.

RESULTS

Among LBW infants (469/1640, 28.6%), chest circumference measures <30.3 cm were 91% sensitive and 83% specific. Similar levels of sensitivity for foot length were achieved only with considerable loss of specificity (<45%). Foot length measurements <6.9 cm were 88% sensitive and 86% specific for the identification of VLBW infants.

CONCLUSION

Chest circumference was superior to foot length in classification of infants into birth weight categories. For the identification of VLBW infants, foot length performed well, and may be preferable to chest circumference, as the former measure does not require removal of infant swaddling clothes. In the absence of more precise direct measures of birth weight, chest circumference is recommended over foot length for the identification of LBW infants.

The neorule: a new instrument to measure linear growth in preterm infants

OBJECTIVES

To compare measurements of crown-heel length (CHL) made with the neorule with CHL measurements made with a stadiometer in term infants. To examine safety and reproducibility of CHL measurements in infants < 32 weeks gestational age (GA) using the neorule.

METHODS

Three measurements of CHL were made by three teams during the first 2 days of life in healthy term infants. One team used the stadiometer and two the neorule. Two different teams made three measurements of CHL on four occasions at two week intervals in infants less than 32 weeks GA. Infants were continuously monitored, and any adverse event was recorded.

RESULTS

Fifty term infants were studied, median (range) birth weight 3440 (2020-5010) g. The mean (SD, 95% confidence interval) difference between values obtained with the stadiometer and neorule was 0.08 (6.22, -1.69 to +1.85) mm and between the two neorule teams was 0.8 (4.48, -0.47 to +2.08) mm. Twenty preterm infants were studied, GA median (range) 29 (25(+0)-31(+6)) weeks, median (range) CHL 397 (339-475) mm. There were no adverse events. The difference (SD, 95%CI) between teams in the mean CHL measurement was 0.18 (4.79, -1.02 to +1.38) mm, with interobserver limit of agreement -9.2 to +9.6 mm and coefficient of variation 1.2%. There were no significant differences between measurements made by single observers; the F ratio was 0.449 (df = 61, p = 0.6).

CONCLUSION

The neorule is a safe and accurate way to measure CHL in newborn infants.

Foot length, an accurate predictor of nasotracheal tube length in neonates

BACKGROUND

Existing guidelines for optimal positioning of endotracheal tubes in neonates are based on scanty data and relate to measurements that are either non-linear or poorly reproducible in sick infants. Foot length can be measured simply and rapidly and is related to a number of external body measurements.

OBJECTIVES

To evaluate the relation of foot length to nasotracheal length in direct measurements at post mortem examinations, and then compare its clinical relevance with traditional weight based estimates in a randomised controlled trial.

METHODS

The dimensions of the upper airway were measured at autopsy in 39 infants with median (range) postmenstrual age and birth weight of 32 (24-43) weeks and 1630 (640-3530) g. The regression equations with 95% prediction intervals were calculated to estimate the optimal nasotracheal length from foot length. In a randomised trial, 59 neonates were nasally intubated according to foot length and body weight based estimates to assess the achievement of "optimal" and "satisfactory" tube placements.

RESULTS

In the direct measurements of the airway at autopsy, foot length was a better predictor of nasotracheal distances (r(2) = 0.79) than body weight, gestational age, and head circumference (r(2) = 0.67, 0.58, and 0.60 respectively). Measurement of foot length was easy and highly reproducible. In the randomised controlled trial, there were no significant differences between the foot length and body weight based estimates in the rates of optimal (44% v 56%) and satisfactory (83% v 72%) endotracheal tube placements.

CONCLUSIONS

Foot length is a reliable and reproducible predictor of nasotracheal tube length and is at least as accurate as the conventional weight based estimation. This method may be particularly valuable in sick unstable infants.

Knee-heel length measurement in healthy preterm infants

AIM

To examine the reproducibility of crown-heel length measurement; the precision and reproducibility of knee-heel length measurement; and the association between the two in healthy preterm infants.

METHODS

Paired crown-heel and knee-heel lengths were measured on 172 occasions by three observers in 43 preterm infants between 205 and 458 days of postconceptional age.

RESULTS

Crown-heel length (CHL) measurement was highly reproducible, with a coefficient of variation (CV) of 0.41%. Knee-heel length (KHL) measurement was relatively precise (CV 0.78%), but less reproducible (intra-observer CV 1.77%, intra-observer CV 2.11%), especially in larger infants. The association between KHL and CHL was not consistent and varied with age. KHL was a poor predictor of CHL, with a 95% predictive interval of +/- 27.5 mm.

CONCLUSIONS

KHL was less reproducible than CHL, especially in larger infants, and a poor predictor of CHL.

Validation of a newly developed mini-knemometer for premature infants

A newly developed knemometric device for lower leg length measurement in premature and newborn infants is presented and validated. The present study was performed to establish a standardized method of use of this instrument. Two independent observers obtained 10 subsequential readings per measurement in three infants over 43 days, after which analysis showed that 5 subsequential readings per measurement gave comparable technical errors. Thirty-one premature infants were assessed by knemometry by two independent observers. The correlation coefficient of all measurements was 0.998. The acquired technical error (mean Standard Deviation (SD) of 5 sequential readings) over a total observation period of 294 days in all studied infants was 0.06 and 0.05 mm, respectively. By a mean lower leg length growth velocity of 0.52 mm per day the technical error amounted to 11% of daily bone growth. The described mini-knemometer is an accurate device for the detection of daily individual growth. A learning period of 21 days is necessary to obtain reliable results.

Knemometry and the assessment of growth in premature babies

The characteristics of a knemometer designed for accurate lower leg measurement in babies were assessed. Repeated measurement of a 100 mm Perspex rod gave a mean length of 99.993 mm and a mean SD of 0.058. When used to measure leg length, technical error of the measurement technique was 0.31 with a mean leg length of 98.49 mm (coefficient of variation 0.31%). Leg lengths measured at birth in 324 babies from 23 to 42 weeks' gestation gave an estimated in utero leg length velocity of 0.43 mm/day (95% confidence interval 0.41 to 0.45). Assessment of interobserver variation showed poor agreement in absolute values of leg length, although similar estimates of leg length velocity could be obtained. The neonatal knemometer allows measurements to be made in situations where conventional growth measurements are not possible. It is believed that knemometry has an important role in accurate evaluation of factors that can influence short term bone growth.

Footlength measurement in the neonate

In 353 neonates, foot length were recorded along with birth weight, crown heel length and head circumference. Foot length correlated well with all three indices (p less than .01). Highest correlation in preterm babies was with crown heel length and weight, and in term babies with head circumference. The formula, length = footlength x 6.5 +/- 20 mm could be correctly used in 95% of babies. When it is difficult to weigh or measure the length accurately, foot length can serve as a useful measurement to assess a baby quickly.

Anthropometric standards for term neonates

32 anthropometric measurements have been carried out (within 48 h of birth) on 106 full-term normal neonates. Trunk and limb parameters are considered and the results presented as mean values with standard deviations. Comparison with previously published standards, where available, showed good agreement. Both sides of the body were measured but no significant difference was found overall between values for left and right sides of the body. The effect of gender on each measurement was also considered with females having significantly smaller head circumferences and head lengths and larger upper leg lengths.

Morphometric study of the fetal development of the human hip joint: significance for congenital hip disease

Hip joints (280) from 140 human fetuses, obtained from abortions and deaths in the perinatal period, were studied. The fetuses ranged from 8.7 to 40 cm in crown-rump length and are believed to be between 12 and 42 weeks in age. The joints were dissected, morphology inspected, and measurements taken of the depth and diameter of the acetabulum, the diameter of the femoral head, length and width of the ligament of the head, the neck-shaft, and torsion angles of the proximal femur. Regression models were fitted to determine which would best predict the growth pattern. Multivariate analysis of variance showed no significant differences between males and females or between the right and left sides. Acetabular depth was shown to be the slowest-growing hip variable, increasing less than fourfold in the period studied. Acetabular indices less than 50 percent indicate a shallow socket at term. Femoral head and acetabular diameter demonstrated a strong relationship (r = 0.860) and in many joints the femoral head diameter exceeded that of the acetabulum. Considerable variability was demonstrated in both femoral angles. The femoral angles showed only low correlation with the other hip variables. These observations indicate that soft tissue structures about the joint must play an important role in neonatal joint stability. The explanation of greater female and left side involvement in congenital hip disease must lie in factors other than growth changes of hip dimensions. Neither angle appears to be a useful indicator of normal joint development.