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Customized GROW vs INTERGROWTH-21^st birthweight standards to identify small for gestational age associated perinatal

Emily Fay¹, Oliver Hugh², Andre Francis²

¹Obstetrical Care Outcomes Assessment Program, Foundation for Health Care Quality, Seattle, WA; Department of Obstetrics and Gynecology, University of Washington, Seattle, WA.

American Journal of Obstetrics & Gynecology MFM

|December 7, 2021

Insights

The customized GROW birthweight standard identified more term infants with fetal growth restriction and adverse outcomes than the INTERGROWTH-21st standard. GROW improved the detection of small for gestational age infants at high risk for stillbirth and other complications.

Area of Science:

Perinatal Medicine
Maternal-Fetal Medicine
Neonatology

Background:

Fetal growth restriction (FGR) is a significant risk factor for stillbirth and adverse pregnancy outcomes.
Accurate assessment of fetal growth is crucial for identifying perinatal risk.

Purpose of the Study:

To evaluate the performance of two international birthweight standards, GROW and INTERGROWTH-21st, in identifying perinatal morbidity and mortality in term infants.
To compare the ability of GROW and INTERGROWTH-21st to detect small for gestational age (SGA) infants at term.

Main Methods:

A retrospective cohort study analyzed data from 92,622 singleton term births (2012-2017).
Infants were classified as SGA (<10th percentile) using customized GROW and INTERGROWTH-21st standards.
Adverse outcomes included stillbirth, neonatal death, low Apgar scores, and neonatal intensive care unit admission.

Main Results:

GROW identified 10.3% of infants as SGA, while INTERGROWTH-21st identified 4.4%.
GROW detected significantly more SGA infants with adverse outcomes, including stillbirths, perinatal deaths, and neonatal complications.
GROW identified 48% of stillbirths classified as SGA by either method, compared to INTERGROWTH-21st's limited identification.

Conclusions:

Customized assessment with the GROW standard enhances the identification of term SGA infants at increased risk for adverse pregnancy outcomes.
The GROW standard demonstrates superior performance in identifying high-risk SGA infants compared to INTERGROWTH-21st.

Read full analysis

Abstract

Background:

Fetal growth restriction is associated with stillbirth and other adverse pregnancy outcomes, and the use of the correct weight standard is an essential proxy indicator of growth status and perinatal risk.

Objective:

This study aimed to assess the performance of two international birthweight standards for their ability to identify perinatal morbidity and mortality indicators associated with small for gestational age infants at term.

Study Design:

This retrospective cohort study used data from a multicenter perinatal quality initiative, including a multiethnic dataset of 125,826 births from 2012 to 2017. Of the singleton term births, 92,622 had complete outcome data including stillbirth, neonatal death, 5-minute Apgar score <7, neonatal glucose instability and need for newborn transfer to a higher level of care or neonatal intensive care unit admission. The customized GROW and INTERGROWTH-21^st birthweight standards were applied to determine small for gestational age (<10th percentile) according to their respective methods and formulae. The associations with adverse outcomes were expressed as relative risks with 95% confidence intervals and population attributable fractions.

Results:

GROW and INTERGROWTH-21^st classified 9578 (10.3%) and 4079 (4.4%) pregnancies as small for gestational age, respectively. For all of the outcomes assessed, GROW identified more small for gestational age infants with adverse outcomes than INTERGROWTH-21^st, including more stillbirths, perinatal deaths, low Apgar scores, glucose instability, newborn seizure, and transfers to a higher level of care. Moreover, 13 of 27 stillbirths (48%) that were small for gestational age by either method were identified as small for gestational age by GROW but not by INTERGROWTH-21^st. Similarly, additional cases of all other adverse outcome indicators were identified by GROW as small for gestational age, whereas INTERGROWTH-21^st identified in only 1 category (glucose instability) 9 of 295 cases (3.1%), which were not identified as small for gestational age by GROW.

Conclusion:

Customized assessment using GROW resulted in increased identification of small for gestational age term infants that were at significantly increased risk of an array of adverse pregnancy outcomes.

Keywords:

GROW INTERGROWTH 21(st)customized charts fetal growth restriction perinatal morbidity small for gestational age stillbirth

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