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Unisex and Sex-Specific Prescriptive Fetal Growth Charts for Improved Detection of Small-for-Gestational-Age Babies
Mariëlle van Roekel1,2, Corine J Verhoeven1,3, Hester D Kamphof4
1Amsterdam UMC location Vrije Universiteit Amsterdam, Midwifery Science, Amsterdam, The Netherlands.
Insights
New fetal growth charts significantly improve the detection of small-for-gestational-age (SGA) birthweight and severe adverse perinatal outcomes (SAPO). Sex-specific charts showed better performance than unisex charts in identifying SGA and severe SGA (sSGA).
Area of Science:
- Obstetrics and Gynecology
- Perinatal Medicine
- Fetal Growth Monitoring
Background:
- Accurate prediction of small-for-gestational-age (SGA) birthweight and severe adverse perinatal outcomes (SAPO) is crucial in low-risk pregnancies.
- Existing descriptive fetal growth charts may have limitations in sensitivity for detecting these conditions.
Purpose of the Study:
- To develop and evaluate sex-specific and unisex prescriptive fetal abdominal circumference (AC) growth charts.
- To compare their performance against a standard descriptive chart in predicting SGA, severe SGA (sSGA), and SAPO.
Main Methods:
- Post hoc analysis of the IRIS study data from 7,704 low-risk women.
- Derivation of IRIS prescriptive unisex and sex-specific AC fetal growth charts using quantile regression.
- Comparison with the descriptive Verburg chart using ultrasound data from 34-36 weeks' gestation.
Main Results:
- IRIS prescriptive charts (sex-specific and unisex) demonstrated over twofold higher sensitivity for SGA and sSGA detection compared to the Verburg chart.
- The sex-specific IRIS chart showed superior performance in identifying male SGA and sSGA compared to the unisex IRIS chart.
- While sensitivity increased, specificity decreased slightly with the IRIS prescriptive charts compared to the Verburg chart.
Conclusions:
- Prescriptive fetal growth charts, particularly sex-specific ones, offer improved detection rates for SGA, sSGA, and SGA with SAPO in low-risk populations.
- The findings support the use of customized, prescriptive fetal growth charts, considering sex, for enhanced perinatal outcome prediction.
- The balance between increased sensitivity and decreased specificity must be considered in clinical application.
Introduction:
Our aim was to develop and evaluate the performance of population-based sex-specific and unisex prescriptive fetal abdominal circumference growth charts in predicting small-for-gestational-age (SGA) birthweight, severe SGA (sSGA) birthweight, and severe adverse perinatal outcomes (SAPO) in a low-risk population.
Methods:
This is a post hoc analysis of the Dutch nationwide cluster-randomized IRIS study, encompassing ultrasound data of 7,704 low-risk women. IRIS prescriptive unisex and IRIS sex-specific abdominal circumference (AC) fetal growth charts were derived using quantile regression. As a comparison, we used the descriptive unisex Verburg chart, which is commonly applied in the Netherlands. Diagnostic parameters were calculated based on the 34-36 weeks' ultrasound.
Results:
Sensitivity rates for predicting SGA and sSGA birthweights were more than twofold higher based on the IRIS prescriptive sex-specific (respectively SGA 43%; sSGA 59%) and unisex (SGA 39%; sSGA 55%) charts, compared to the Verburg chart (SGA 16%; sSGA 23% both p < 0.01). Specificity rates were highest for Verburg (SGA 99%; sSGA 98%) and lowest for IRIS sex-specific (SGA 94%; sSGA 92%). Results for predicting SGA with SAPO were similar for the prescriptive charts (44%), and again higher than the Verburg chart (20%). The IRIS sex-specific chart identified significantly more males as SGA and sSGA (respectively, 42%; 60%, p < 0.001) than the IRIS unisex chart (respectively, 35%; 53% p < 0.01).
Conclusion:
Our study demonstrates improved performance of both the IRIS sex-specific and unisex prescriptive fetal growth compared to the Verburg descriptive chart, doubling detection rates of SGA, sSGA, and SGA with SAPO. Additionally, the sex-specific chart outperformed the unisex chart in detecting SGA and sSGA. Our findings suggest the potential benefits of using prescriptive AC fetal growth charts in low-risk populations and emphasize the importance of considering customizing fetal growth charts for sex. Nevertheless, the increased sensitivity of these charts should be weighed against the decrease in specificity.
