**Contents**

Anthropometry Domain

IntroductionSubjective methods- Introduction to Subjective Methods
- Birth weight
- Body shape
- Weight and height
- Waist and hip circumference

- Introduction to Objective Methods
- Simple measures - stature
- Simple measures - weight
- Simple measures - circumference
- Simple measures - arm anthropometry
- Simple measures - skinfolds
- Simple measures - abdominal sagittal diameter
- Simple measures - head circumference
- Bioelectric impedance analysis
- Multi-component models
- Hydrostatic underwater weighing
- Air displacement plethysmography
- Hydrometry
- Whole body DEXA scan
- Near infrared interactance
- Whole body counting of total body potassium
- 3d photonic scan
- Magnetic resonance imaging (MRI) / Magnetic resonance spectroscopy (MRS)
- Total body electrical conductivity (TOBEC)
- Computed tomography (CT)
- Ultrasonography

- Introduction anthropometric indices
- Body mass index
- Fat and fat free mass indices
- Ponderal index
- Percentiles and Z-scores

- Anthropometry Video Resources
- Height procedure
- Protocol for measuring waist circumference
- Measuring hip circumference
- Weight and body composition procedure

Rohrer’s Ponderal Index (PI) is an indication of a person’s weight relative to their height, and is used as a proxy measure of adiposity, similar to the Body Mass Index (BMI). PI is calculated as weight (kg) divided by cubed height (m^{3})
(du V. Florey, 1970).

Compared to the more commonly used proxy for body fat BMI, (the person’s weight divided by the square of their height), PI better corrects for height, and therefore is a better estimate of adiposity, among **newborn infants** and also in
the **adolescent population** (Peterson et al, 2017).

At birth, PI can be used to assess the pattern of fetal growth in small-for-gestational-age (SGA) infants (Armangil et al, 2011), by distinguishing symmetric from asymmetric intrauterine growth restriction, and quantifying the severity of asymmetry in growth-restricted neonates.

- PI is calculated using measurements of height (or length) and weight.
- The units of measurement (e.g. metric vs. imperial) must be clearly stated to avoid errors.

- PI estimates proportionality.
- At birth, PI is used in clinical settings, in nutritional surveys and large scale population studies as a screening tool to indicate whether a newborn infant is underweight, overweight, or a normal weight for their length. It is an indicator of fetal growth restraint: SGA is sometimes defined as a PI <3
^{rd}percentile for gestational age and sex (Walther and Ramaekers, 1982). - PI has also been suggested to be a better proxy than BMI for adiposity among adolescents (Peterson et al, 2017), however is not yet widely used in this population.

If using the **metric system**, PI is calculated as body weight divided by
the cube root of
height, where weight is in kilograms and height in meters.

PI = Weight (kg) / [Height (m)]^{3}

Other variables might be needed for the interpretation of this index such as sex, age and gestational age, however population reference data on PI are not widely available.

In infancy, like the other growth indices, PI can be independently assessed by the percentile point achieved by a child relative to the healthy children of that age and sex in the same population.
Median (or the 50^{th} percentile) is regarded as a reference value, and 3^{rd} and 97^{th} percentiles as thresholds to indicate abnormally low or abnormally high values. A PI <10^{th} percentile reflects fetal malnutrition;
a PI <3^{rd} percentile indicates severe fetal wasting. While a PI >90^{th} percentile was defined as neonatal overweight.

**Strengths**

- PI is a important indicator of fetal malnutrition.
- Easy to measure.
- Non-invasive.
- Among newborn infants and adolescents, PI is less correlated with height and length and is therefore a better proxy measure of adiposity than BMI.

**Limitations**

- PI is only a proxy measure of adiposity, but does not directly assess the proportions of fat and fat-free mass.
- In newborns, interpretation of PI values requires data on sex and gestational age and comparison to reference data.

Considerations relating to the use of ponderal index in specific populations are described in Table 1.

**Table 1** Application of ponderal index in different populations.

Population | Comment |
---|---|

Pregnancy | Not suitable. |

Infancy and lactation | Suitable. |

Toddlers and young children | Not suitable as population reference not available. |

Adolescents | Suitable. |

Adults | Suitable, however BMI more commonly used. |

Older Adults | Suitable, however BMI more commonly used. |

Ethnic groups | Not suitable as population reference not available. |

Other (obesity) | Suitable. |

Refer to section: practical considerations for objective anthropometry

Resources are dependent on the instruments/methods used to derive the raw data of height and weight.

- Armangil D, Yurdakok M, Korkmaz A, Yigit S, Tekinalp G. Ponderal index of large-for-gestational age infants: comparison between infants of diabetic and non-diabetic mothers. The Turkish journal of pediatrics. 2011;53(2):169-72. Epub 2011/08/23.
- Fay RA, Dey PL, Saadie CM, Buhl JA, Gebski VJ. Ponderal index: a better definition of the 'at risk' group with intrauterine growth problems than birth-weight for gestational age in term infants. The Australian & New Zealand journal of obstetrics & gynaecology. 1991;31(1):17-9. Epub 1991/02/01.
- Florey Cdu V. The use and interpretation of ponderal index and other weight-height ratios in epidemiological studies. Journal of chronic diseases. 1970;23(2):93-103. Epub 1970/08/01.
- Grandi C, Tapia JL, Marshall G, Grupo Colaborativo N. [An assessment of the severity, proportionality and risk of mortality of very low birth weight infants with fetal growth restriction. A multicenter South American analysis]. Jornal de pediatria. 2005;81(3):198-204.
- Epub 2005/06/14. Evaluacion de la severidad, proporcionalidad y riesgo de muerte de recien nacidos de muy bajo peso con restriccion del crecimiento fetal. Analisis multicentrico sudamericano.
- Huber NM. Ponderal index and height. American journal of physical anthropology. 1969;31(2):171-5. Epub 1969/09/01.
- Lehingue Y, Remontet L, Munoz F, Mamelle N. Birth ponderal index and body mass index reference curves in a large population. American journal of human biology : the official journal of the Human Biology Council. 1998;10(3):327-40. Epub 1998/01/01.
- Oluwafemi OR, Njokanma FO, Disu EA, Ogunlesi TA. Current pattern of Ponderal Indices of term small-for-gestational age in a population of Nigerian babies. BMC pediatrics. 2013;13:110. Epub 2013/07/24.
- Persson M, Pasupathy D, Hanson U, Norman M. Birth size distribution in 3,705 infants born to mothers with type 1 diabetes: a population-based study. Diabetes care. 2011;34(5):1145-9. Epub 2011/03/25.
- Peterson CM, Su H, Thomas DM, Heo M, Golnabi AH, Pietrobelli A, et al. Tri-Ponderal Mass Index vs Body Mass Index in Estimating Body Fat During Adolescence. JAMA pediatrics. 2017;171(7):629-36. Epub 2017/05/16.
- Sharma D, Shastri S, Sharma P. Intrauterine Growth Restriction: Antenatal and Postnatal Aspects. Clinical medicine insights Pediatrics. 2016;10:67-83. Epub 2016/07/22.
- Walther FJ, Ramaekers LH. Neonatal morbidity of S.G.A. infants in relation to their nutritional status at birth. Acta paediatrica Scandinavica. 1982;71(3):437-40. Epub 1982/05/01.
- http://www.medicalbiostatistics.com/childhealth.pdf