Fig 1.
Participant Flowchart.
Table 1.
Abbreviations for Clinical Measures Used the Text.
Table 2.
Enrolment Characteristics of Pregnant Women (n = 688) from Rural Madang Province, Papua New Guinea, 2009–2012.
Fig 2.
Box-and-Whisker Charts of Estimated GA at Delivery by Method.
The continuous bold line denotes the median of the reference and dashed lines denote 5% and 95% centiles of the reference.
Table 3.
Comparison of Clinical and Late Ultrasound Estimates of Gestational Age Against Reference Ultrasound.
Fig 3.
Bland-Altman Plots and Levels of Agreement.
A) BS (external); B) BS (neuromuscular); C) BS (total); D) LMP; E) mid-pregnancy ultrasound; F) late-pregnancy ultrasound; G) linear SFH model; H) sequential SFH model; I) Quickening; J) corrected LMP*. The continuous horizontal lines are average levels of agreement. The dashed lines denote the 95% levels of agreement between the clinical estimators and the reference method. R represents the Pearson correlation coefficient and p values indicate significance of the parametric correlations. Significant trends are present in all comparisons, indicating significant variability in the bias across the data range. The correlations are all positive, meaning that the clinical estimators tend to further underestimate lower estimates of GA, which is demonstrated by the high number of PTB predicted by most clinical methods (Table 4).
Table 4.
Sensitivity and Specificity of Clinical and Late Ultrasound Estimates of Gestational Age against Gold-Standard Ultrasound to Predict Preterm Birth in Comparison to the Reference Method (n = 688 with 5.2% (36) Diagnosed Preterm Birth).
Fig 4.
Receiver Operating Characteristic Space for Mid- and Late-Pregnancy USS and Clinical Estimators to Predict PTB.
Note that the insets are magnifications of the regions of interest (outlined by the dotted lines). The solid gray lines with gray numbering are the F-measure isolines in the receiver operating characteristic space. BS(e): external BS; BS(n): neuromuscular BS; BS(t): total BS; LMP: last menstrual period; mid-scan: mid-pregnancy USS; late-scan: late-pregnancy USS; 1x SFH: linear SFH model; 3x SFH: sequential SFH model; LMP/SFH: LMP/SFH model; LMP*: corrected LMP according to PNG guidelines.
Table 5.
Multiple Regression Models and Performance in Predicting Gestational Age and Preterm Birth.