%0 Journal Article
%T Impact of analysis technique on our understanding of the natural history of labour: a simulation study.
%A de Vries BS
%A Mcdonald S
%A Joseph FA
%A Morton R
%A Hyett JA
%A Phipps H
%A McGeechan K
%J BJOG
%V 128
%N 11
%D 10 2021
%M 33837643
%F 7.331
%R 10.1111/1471-0528.16719
%X To evaluate the discrepancy between historical and more recent descriptions of the first stage of labour by testing whether the statistical techniques used recently (repeated-measures polynomial and interval-censored regression) were appropriate for detection of periods of rapid acceleration of cervical dilatation as might occur at the time of transition from a latent to an active phase of labour.<BR>A simulation study using regression techniques.<BR>We created a simulated data set for 500 000 labours with clearly defined latent and active phases using the parameters described by Friedman. Additionally, we created a data set comprising 500 000 labours with a progressively increasing rate of cervical dilatation.<BR>Repeated-measures polynomial regression was used to create summary labour curves based on simulated cervical examinations. Interval-censored regression was used to create centimetre-by-centimetre estimates of rates of cervical dilatation and their 95th centiles.<BR>Labour summary curves and rates of cervical dilatation.<BR>Repeated-measures polynomial regression did not detect the rapid acceleration in cervical dilatation (i.e. acceleration phase) and overestimated lengths of labour, especially at smaller cervical dilatations. There was a two-fold overestimation in the mean rate of cervical dilatation from 4 to 6 cm. Interval-censored regression overestimated median transit times, at 4- to 5-cm cervical dilatation or when cervical examinations occurred less frequently than 0.5- to 1.5-hourly.<BR>Repeated-measures polynomial regression and interval-censored regression should not be routinely used to define labour progress because they do not accurately reflect the underlying data.<BR>Repeated-measures polynomial and interval-censored regression techniques are not appropriate to model first stage of labour.