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. 2020 Oct;29(10):2795-2813.
doi: 10.1177/0962280220905623. Epub 2020 Mar 23.

Correlation models for monitoring fetal growth

Yuan Feng  1 , Luo Xiao  1 , Cai Li  1 , Stephanie T Chen  1 , Eric O Ohuma  2   3
Affiliations

Correlation models for monitoring fetal growth

Yuan Feng et al. Stat Methods Med Res. 2020 Oct.

Abstract

Ultrasound growth measurements are monitored to evaluate if a fetus is growing normally compared with a defined standard chart at a specified gestational age. Using data from the Fetal Growth Longitudinal Study of the INTERGROWTH-21st project, we have modelled the longitudinal dependence of fetal head circumference, biparietal diameter, occipito-frontal diameter, abdominal circumference, and femur length using a two-stage approach. The first stage involved finding a suitable transformation of the raw fetal measurements (as the marginal distributions of ultrasound measurements were non-normal) to standardized deviations (Z-scores). In the second stage, a correlation model for a Gaussian process is fitted, yielding a correlation for any pair of observations made between 14 and 40 weeks. The correlation structure of the fetal Z-score can be used to assess whether the growth, for example, between successive measurements is satisfactory. The paper is accompanied by a Shiny application, see https://lxiao5.shinyapps.io/shinycalculator/.

Keywords: Fetal health; correlation; longitudinal study; reference chart.

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Figures

Figure 1.
Figure 1.
Distribution of Gestational Age at which measurements were recorded (with expected periodicity of 5 weeks).
Figure 2.
Figure 2.
Estimated location, scale and skewness parameters as functions of gestational age for the five fetal growth measurements.
Figure 3.
Figure 3.
Estimated kurtosis parameters as functions of gestational age for the five fetal growth measurements using BCPE and BCT.
Figure 4.
Figure 4.
Smooth estimates of the first to fourth moments of the constructed Z-scores for AC, FL, HC, BPD and OFD.
Figure 5.
Figure 5.
Further comparison of BCCG (solid), BCPE (dashed) and BCT (dotted) on the fourth moments of Z-scores.
Figure 6.
Figure 6.
Temporal correlations of standardized AC with different correlation models.
Figure 7.
Figure 7.
Temporal correlations of standardized FL with different correlation models.
Figure 8.
Figure 8.
Temporal correlations of standardized HC with different correlation models.
Figure 9.
Figure 9.
Temporal correlations of standardized BPD with different correlation models.
Figure 10.
Figure 10.
Temporal correlations of standardized OFD with different correlation models.
Figure 11.
Figure 11.
Observed growth trajectory (linked triangles) and predicted measurements (dots) given previous observations of a randomly selected fetus. Dashed line is the population mean.
See this image and copyright information in PMC

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