Outcome measures
Data were stratified by CGA presence or absence on TVUS. The primary
outcome was spontaneous PTB <37 weeks gestation. Secondary
outcomes included the prediction of PTB by quantifiable measures of CGA
when present, and the impact of CGA assessment on CL screening for the
prediction of the primary outcome. Present CGA was defined as a
well-demarcated hyper- or hypoechoic region lining the cervical canal,
distinct in echotexture from the peripheral cervical stroma. To attempt
to quantify the extent of the CGA if present, the visualized CGA was
measured for visualized length (calipers parallel to the cervical
canal), as well as widest and narrowest widths (calipers perpendicular
to the cervical canal). Average widths were calculated from the widest
and narrowest width measurements. Approximate areas of the CGA were
calculated by multiplying the measured parameters, estimating an
approximately rectangular CGA overlying a linear cervical canal in the
sagittal view.