This version was machine-translated from German and has not been medically reviewed. The authoritative version is the German version.

INTERGROWTH-21st postnatal growth of preterm infants

Weight, length, head circumference and weight for length 27–64 weeks postmenstrual; gain needed to hold the percentile

About this calculator

Percentiles and z-scores of weight, length, head circumference and weight for length according to the INTERGROWTH-21st Postnatal Growth Standard for preterm infants (Villar 2015), 27–64 weeks postmenstrual. For the course after birth, not for classification at birth. From 64 weeks the WHO curves with corrected age apply.

Postmenstrual age = gestational age at birth + chronological age. The curves are interpolated here to the exact day.

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Reference and license

INTERGROWTH-21st Postnatal – 27–64 weeks postmenstrual.
Villar J, Giuliani F, Bhutta ZA, et al. Postnatal growth standards for preterm infants: the Preterm Postnatal Follow-up Study of the INTERGROWTH-21st Project. Lancet Glob Health. 2015;3(11):e681–e691. License: terms of use of the INTERGROWTH-21st data not clarified (portal intergrowth21.com public and free of charge; whether use in a calculator is permitted is not documented). Coefficients from the R package gigs (LSHTM, github.com/lshtm-gigs/gigs); its GPL ≥ 3 license applies to the R code, not to the data. Only the calculation has been reproduced here, no code adopted. Source
Standard for preterm infants (born under 37+0 weeks) without severe illness, for the course after birth up to 64 weeks postmenstrual; thereafter WHO curves with corrected age. Not for classification at birth.
INTERGROWTH-21st Postnatal weight for length – 35–65 cm length.
Villar J, Giuliani F, Bhutta ZA, et al. Lancet Glob Health. 2015;3(11):e681–e691. Weight-for-length coefficients from Eric Ohuma (INTERGROWTH-21st), according to gigs. License: terms of use of the INTERGROWTH-21st data not clarified (portal intergrowth21.com public and free of charge; whether use in a calculator is permitted is not documented). Coefficients from the R package gigs (LSHTM, github.com/lshtm-gigs/gigs); its GPL ≥ 3 license applies to the R code, not to the data. Only the calculation has been reproduced here, no code adopted. Source

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Note

Calculation aid for healthcare professionals. Percentiles and z-scores describe the position of a measured value in the reference population; clinical assessment remains with the treating physician.

Review date of the German original: 2026-11-08 · Methodology

Frequently asked questions

INTERGROWTH-21st postnatal growth of preterm infants: What does this calculator compute?

INTERGROWTH-21st postnatal growth of preterm infants: Which sources is this calculator based on?

Villar J, Giuliani F, Bhutta ZA, et al. Postnatal growth standards for preterm infants: the Preterm Postnatal Follow-up Study of the INTERGROWTH-21st Project. Lancet Glob Health. 2015;3(11):e681–e691.; Villar J, Giuliani F, Bhutta ZA, et al. Lancet Glob Health. 2015;3(11):e681–e691. Weight-for-length coefficients from Eric Ohuma (INTERGROWTH-21st), according to gigs.