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Published on: February 2, 2017
Conditional standards for the quantification of foetal growth in an ethnic Chinese population: a longitudinal study
Jian Jiang1, Xiaodan Zhu1, Linyu Zhou1
1Department of Ultrasound Medicine, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
Insights
This study developed conditional growth standards for fetal biometry in ethnic Chinese populations using longitudinal ultrasound data. These standards enable better assessment of fetal growth and can aid in identifying risks for adverse outcomes.
Area of Science:
- Maternal-Fetal Medicine
- Prenatal Diagnostics
- Biometry and Growth Standards
Background:
- Existing fetal biometry charts for ethnic Chinese populations primarily use cross-sectional data, limiting assessment to fetal size rather than growth.
- Longitudinal data from serial fetal measurements are crucial for accurately assessing both fetal size and growth patterns.
Purpose of the Study:
- To construct conditional growth standards for key fetal biometric variables (BPD, HC, AC, FL) in an ethnic Chinese population.
- To provide a practical tool, such as a spreadsheet, for implementing these conditional standards in clinical settings.
Main Methods:
- An observational study involving 1289 fetuses from low-risk singleton pregnancies in an ethnic Chinese population.
- Repeated ultrasound measurements of biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) were collected.
- A linear mixed model with fractional polynomial regression was employed to analyze the longitudinal data and construct the standards.
Main Results:
- Longitudinal equations for the mean and variance of BPD, HC, AC, and FL were established for the ethnic Chinese population.
- Conditional percentiles (Z-scores) can be calculated using these equations and prior measurements for individual fetuses.
- A spreadsheet tool was developed for easy implementation and querying of the conditional standards.
Conclusions:
- The developed conditional standards offer a more accurate method for assessing fetal growth in ethnic Chinese pregnancies compared to cross-sectional data.
- These standards have direct implications for clinical practice, enabling better monitoring of fetal development.
- Future research can utilize these standards to investigate the association between abnormal fetal growth patterns and adverse pregnancy outcomes.
Abstract:
This was an observational study of low-risk singleton pregnancies in an ethnic Chinese population. Foetal biometric variables which included biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL) were measured repeatedly. The standard views for measurement were obtained according to INTERGROWTH-21st criteria. A linear mixed model with fractional polynomial regression was used to describe the longitudinal design. The study included 1289 foetuses and a total of 5125 ultrasound scans, of which each foetus was scanned at least three times, the intervals between scans being at least two weeks. The parameters of the linear mixed models were estimated by Stata v.16 (College Station, TX). Using these parameters, the equations of the mean and variance for BPD, HC, AC and FL were constructed. The conditional percentiles or Z scores could be calculated based on the above equations and previous measurements of the same foetus. A spreadsheet was provided for implementation.Impact StatementWhat is already known on this subject? Longitudinal data derived from serial measurements are therefore appropriate for assessing both foetal size and foetal growth. At present, most reference charts of ethnic Chinese foetal biometry are derived from cross-sectional data, which can only assess foetal size.What do the results of this study add? In this study, we have constructed conditional standards for foetal biometry in an ethnic Chinese population and provided a spreadsheet for querying.What are the implications of these findings for clinical practice and/or further research? The conditional standards can be used to assess foetal growth in clinical practice. In the future, we hope that these foetal growth standards can be applied to determine whether abnormal growth increases the risk of adverse outcomes.
