Objective To develop and validate a computerised algorithm for the interpretation of the characteristics of fetal heart rate monitoring in labour.

Design Prospective observational study.

Setting Labour ward in a tertiary hospital.

Sample Intrapartum cardiotocograms from 24 pregnancies.

Methods A computerised algorithm was developed to assess the fetal heart baseline rate, variability, the number of accelerations and the number of decelerations. Twenty five minute segments of cardiotocograms were interpreted by the algorithm and also by seven expert reviewers independently. The reviewers were unaware of the outcome of labour. The reliability of the characteristics of car-diotocography and the validity of the computerised algorithm were assessed using the intraclass correlation coefficient and weighted kappa statistic for continuous and ordinal variables respectively.

Results The inter rater reliability of the baseline fetal heart rate and the number and type of decelerations was good (intraclass correlation coefficient 0.93, 0.93 and 0.79, respectively). The reliability of baseline variability (kappa = 0.27) and accelerations (intraclass correlation coefficient = 0.27) was poor. The computerised algorithm had good agreement with the reviewers for the baseline fetal heart rate (intraclass correlation coefficient 0.91 to 0.98) and the number of decelerations (intraclass correlation coefficient 0.82 to 0.91), but was less valid as regards the number of late decelerations (intraclass correlation coefficient 0.68 to 0.85) and the number of accelerations (intraclass correlation coefficient 0.06 to 0.80), and was invalid as regards baseline variability (kappa 0.00 to 0.34).

Conclusions The high level of validity of the computerised algorithm for the estimation of the baseline fetal heart rate and the number of decelerations justifies its further technical development.