A prospective longitudinal and cross-sectional study of FHR was performed on 110 healthy multiparae during normal labour. Auscultations during 15 second-periods were performed immediately after a contraction and 1 min later and related to the station of the fetal head. No significant differences in mean-FHR were found between related early and late observations during the whole process of labour.
The mean-FHR decreased significantly during the passage of the fetus through the birth canal. During the second stage the cross-sectional biological variation of FHR was twice as large as during the first stage. In the individual subject the maximal difference between related early and late observations following a contraction increased with 70% when the fetal head reached the pelvic floor.
The data are compared with those from a previous investigation on nulliparae. Auscultograms for practical clinical use are presented.