Produced as part of the Guidance for International Growth Standards (GIGS)
project, gigs provides a single, simple interface for working with the WHO
Child Growth Standards and outputs from the INTERGROWTH-21st project.
You will find functions for converting between anthropometric measures (e.g.
weight or length) to z-scores and centiles, and the inverse. Also included is a
command for classifying newborn and infant growth according to published
z-score/centile cut-offs.
The gigs package is available for Stata version 16 and over. You can install
the latest stable release of gigs from GitHub using the
github module for Stata:
. github install lshtm-gigs/gigs-stataAlternatively, you can download a stable release of your choice from GitHub
using the net install command from Stata. Simply go to the stable release
of gigs that you want to download from the
releases page on GitHub,
and download the zipped archive. Unzip this downloaded archive. Within this
unzipped folder will be another folder, inside which will be the .ado/.dta
files needed for gigs to work. Put the path to the folder containing the
.ado/.dta files in the from() option of net install, and Stata will
install the necessary files.
. net install gigs, from("directory/of/unzipped/folder/with/ado/files")-
ig_nbs- INTERGROWTH-21st standards for newborn sizeComponent standards
Acronym Description Unit gest_days()rangewfgaWeight-or-gestational age kg 168 to 300 days lfgaLength-for-gestational age cm 168 to 300 days hcfgaHead circumference-for-gestational age cm 168 to 300 days wlrfgaWeight-to-length ratio-for-gestational age kg/cm 168 to 300 days ffmfgaFat-free mass-for-gestational age kg 266 to 294 days bfpfgaBody fat percentage-for-gestational age % 266 to 294 days fmfgaFat mass-for-gestational age kg 266 to 294 days
-
ig_png- INTERGROWTH-21st standards for postnatal growth in preterm infantsComponent standards
Acronym Description Unit xvar()rangewfaweight-for-age kg 27 to ≤64 weeks PMA lfalength-for-age cm 27 to ≤64 weeks PMA hcfahead circumference-for-age cm 27 to ≤64 weeks PMA wflweight-for-length kg 35 to 65 cm
-
ig_fet- INTERGROWTH-21st fetal standardsComponent standards
Acronym Description Unit xrangehcfgahead circumference-for-GA mm 98 to 280 days bpdfgabiparietal diameter-for-GA mm 98 to 280 days acfgaabdominal circumference-for-GA mm 98 to 280 days flfgafemur length-for-GA mm 98 to 280 days ofdfgaoccipito-frontal diameter for-GA mm 98 to 280 days efwfgaestimated fetal weight-for-GA grams 154 to 280 days sfhfgasymphisis-fundal height-for-GA mm 112 to 294 days crlfgacrown-rump length-for-GA mm 58 to 105 days gafcrlGA-for-crown-rump length days 15 to 95 mm gwgfgagestational weight gain-for-GA kg 98 to 280 days pifgapulsatility index-for-GA 168 to 280 days rifgaresistance index-for-GA 168 to 280 days sdrfgasystolic/diastolic ratio-for-GA 168 to 280 days tcdfgatranscerebellar diameter-for-GA mm 98 to 280 days gaftcdGA-for-transcerebellar diameter days 12-55 mm poffgaparietal-occipital fissure-for-GA mm 105 to 252 days sffgaSylvian fissue-for-GA mm 105 to 252 days avfgaanterior horn of the lateral ventricle-for-GA mm 105 to 252 days pvfgaatrium of the posterior horn of the lateral ventricle-for-GA mm 105 to 252 days cmfgacisterna magna-for-GA mm 105 to 252 days hefwfgaHadlock estimated fetal weight-for-GA g 126 to 287 days
-
who_gs- WHO Child Growth Standards for term infantsComponent standards
Acronym Description Unit xvar()rangewfaweight-for-age kg 0 to 1856 days bfaBMI-for-age kg/m2 0 to 1856 days lhfalength/height-for-age cm 0 to 1856 days hcfahead circumference-for-age cm 0 to 1856 days wflweight-for-length kg 45 to 110 cm wfhweight-for-height kg 65 to 120 cm acfaarm circumference-for-age cm 91 to 1856 days ssfasubscapular skinfold-for-age mm 91 to 1856 days tsfatriceps skinfold-for-age mm 91 to 1856 days
Each conversion function has similar syntax. The main function call determines
the set of standards in use, the acronym parameter specifies which component
standard is being used, and the conversion parameter specifies the type of
conversion you wish to perform. This conversion parameter can take one of four
values: "v2z" (value-to-z-score), "v2c" (value-to-centile), "z2v"
(z-score-to-value), "c2v" (centile-to-value). The sex() and sexcode()
options supply the non-fetal functions with sex data - without this, these
sex-specific growth standards cannot be applied.
This function can be used to convert between measurements and z-scores/centiles in each of the INTERGROWTH-21st Newborn Size Standards.
The extend option, when specified, allows the function to use extrapolated
versions of these INTERGROWTH-21st standards which can take
gestational ages from 154 to 314 days (22+0 to 44+6 weeks)
when acronym is one of "wfga", "lfga", or "hcfga". Our process for
extrapolating these standards is documented
here.
This function can be used to convert between measurements and z-scores/centiles in each of the INTERGROWTH-21st Postnatal Growth of Preterm Infants Standards.
This function can be used to convert between measurements and z-scores/centiles in each of the INTERGROWTH-21st Fetal standards.
This function can be used to convert between measurements and z-scores/centiles in each of the WHO Child Growth Standards.
The gigs_classify_growth command is used to classify infant growth according to
published cut-offs. These publications are discussed in the attached paper.
The outcome argument is used to pick specific growth analyses, or you can run
all growth analyses by using all.
-
all- Generate variables for all growth outcomes -
sfga- Generate variables for size for gestational ageValues and labels for generated variables
sfgaandsfga_severeValue Meaning Centile range -2 Severely small for gestational age <3rd -1 Small for gestational age (SGA) <10th 0 Appropriate for gestational age (AGA) 10th to 90th 1 Large for gestational age (LGA) >90th -
svn- Generate variables for small vulnerable newbornsValues and labels for generated variable
svnValue Meaning Term Status Centile range -4 Preterm SGA Preterm <10th -3 Preterm AGA Preterm 10th to 90th -2 Preterm LGA Preterm >90th -1 Term SGA Term <10th 0 Term AGA Term 10th to 90th 1 Term LGA Term >90th -
stunting- Generate variables for stuntingValues and labels for generated variables
stuntingandstunting_outliersValue Meaning Z-score range -2 Severe stunting -5 to -3 -1 Stunting -3 to -2 0 Not stunting -2 to 5 -10 Implausible <-5 or >5 -
wasting- Generate variables for wastingValues and labels for generated variables
wastingandwasting_outliersValue Meaning Z-score range -2 Severe wasting -5 to -3 -1 Wasting -3 to -2 0 Not wasting -2 to 2 1 Overweight 2 to 5 -10 Implausible <-5 or >5 -
wfa- Generate variables for weight-for-ageValues and labels for generated variables
wfaandwfa_outliersValue Meaning Z-score range -2 Severely underweight -6 to -3 -1 Underweight -3 to -2 0 Normal weight -2 to 2 1 Overweight 2 to 5 -10 Implausible <-6 or >5 -
headsize- Generate variables for head sizeValues and labels for generated variable
headsizeValue Meaning Z-score range -2 Severe microcephaly <-3 -1 Microcephaly -3 to -2 0 Normal weight -2 to 2 1 Microcephaly -3 to -2 2 Severe microcephaly >3
This section illustrates a possible use case using life6mo.dta, an extract of
data from the Low birthweight Infant Feeding Exploration (LIFE) Study. It
contains weight measurements for term and preterm infants from birth
(visitweek == 0) to around six months of age (visitweek == 26).
. use life6mo, clear
. keep id gestage sex visitweek pma age_days weight_g
. local 37weeks 7 * 37
. list in f/9, noobs abbreviate(10) sep(9)
__________________________________________________________
| id gestage sex visitweek pma age_days weight_g |
| 1 273 1 0 273 0 2300 |
| 1 273 1 1 280 7 2185 |
| 1 273 1 2 288 15 2325 |
| 1 273 1 4 301 28 2575 |
| 1 273 1 6 316 43 3410 |
| 1 273 1 10 344 71 4262.3333 |
| 1 273 1 14 376 103 5050 |
| 1 273 1 18 399 126 5431.6667 |
| 1 273 1 26 460 187 5835 |
‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾We can use the conversion functions listed above to generate weight-for-age z-scores (WAZs) in the different study populations (i.e. term vs preterm) and measurement timings (i.e. z-scores for newborns with INTERGROWTH-21st Newborn Size Standards, WHO/INTERGROWTH Postnatal standards after birth).
. egen double waz_nbs = ig_nbs(weight_g/1000, "wfga", "v2z") ///
> if age_days == 0, ///
> gest_days(gestage) sex(sex) sexcode(m=1, f=2)
(2,432 missing values generated)
. egen double waz_who = who_gs(weight_g/1000, "wfa", "v2z") ///
> if age_days > 0 & gestage >= `37weeks´, ///
> xvar(age_days) sex(sex) sexcode(m=1, f=2)
(1,360 missing values generated)
. gen pma_weeks = pma / 7
. egen double waz_png = ig_png(weight_g/1000, "wfa", "v2z") ///
> if age_days > 0 & gestage < `37weeks´, ///
> xvar(pma_weeks) sex(sex) sexcode(m=1, f=2)
(1,463 missing values generated)
. drop pma_weeksWe can then combine these WAZs into one overall waz variable:
. gen double waz = waz_who if gestage > `37weeks´
(1,508 missing values generated)
. replace waz = waz_png if gestage < `37weeks´
(1,026 real changes made)
. replace waz = waz_nbs if age_days == 0
(57 real changes made)
. list visitweek gestage pma waz_* waz in f/9, noobs sep(9)
____________________________________________________________________
| visitw~k gestage pma waz_nbs waz_who waz_png waz |
| 0 273 273 -2.298544 . . -2.298544 |
| 1 273 280 . -3.028356 . -3.028356 |
| 2 273 288 . -3.2685948 . -3.2685948 |
| 4 273 301 . -3.6824586 . -3.6824586 |
| 6 273 316 . -2.7962372 . -2.7962372 |
| 10 273 344 . -2.5495876 . -2.5495876 |
| 14 273 376 . -2.3102437 . -2.3102437 |
| 18 273 399 . -2.3030732 . -2.3030732 |
| 26 273 460 . -2.8157742 . -2.8157742 |
‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾This waz variable can then be used to determine whether infants are
underweight at different age points, or to track the growth trajectory of
individual children.
This dataset contains information on weight at birth, so could be used to
calculate size-for-gestational age classifications. The
gigs_classify_growth command will automatically pick out birth
observations, and compute size-for-GA in these observations:
. use life6mo, clear
. gen wt_kg = weight_g / 1000
. gigs_classify_growth sfga, ///
> gest_days(gestage) sex(sex) sexcode(m=1, f=2) ///
> weight_kg(wt_kg) id(id)
Requested outcomes:
Size-for-gestational age (sfga)
NOTE: There were 231 birth observations where `age_days' > 0.5.
NOTE: There was 1 birth measure where an infant was too old for the
INTERGROWTH-21st Newborn Size standards (`gest_age' > 300).
This infant will be assessed with the WHO Growth Standards instead.
Supplied data:
Weight in kg
Running analyses. New/replaced variables:
Generated new variable birthweight_centile.
Generated new variable sfga.
Generated new variable sfga_severe.
. tab sfga
sfga | Freq. Percent Cum.
------------+-----------------------------------
SGA | 185 64.46 64.46
AGA | 88 30.66 95.12
LGA | 14 4.88 100.00
------------+-----------------------------------
Total | 287 100.00We request that users note any bugs, issues, or feature requests on the GitHub issues page.
S. R. Parker
Maternal, Adolescent, Reproductive, and Child Health Centre
London School of Hygiene & Tropical Medicine
Dr L. Vesel
Ariadne Labs, Brigham and Women’s Hospital
Harvard T.H. Chan School of Public Health
Professor E. O. Ohuma
Maternal, Adolescent, Reproductive, and Child Health Centre
London School of Hygiene & Tropical Medicine