A more detailed study of the distribution of grade-3 FHRA by
20-min sequences for cases and controls (Table 2) revealed a
significant association between grade-3 FHRA and uterine rupture
in the hour preceding its diagnosis (odds ratio ranging from
3.7 [1.2–11.3] in the 20 min before childbirth to 4.3 [1.4–13.0] for the 40–20 min interval before childbirth, with overlapping
confidence intervals).