Antepartum fetal heart rate monitoring. II. Deceleration patterns.

Fetal heart rate was studied during the antepartum period in 246 patients, yielding a total of 1964 recordings. The following parameters were evaluated and correlated: --the semi-quantitative assessment of fetal heart rate instability (as expressed by the percentage of duration of flat traces); --the presence of decelerations and their relationship to the presence or absence of uterine contractions; --the neonatal condition. Overall, 50% of the patients exhibited uterine contractions while 30% contained decelerations patterns either occurring spontaneously or in association with uterine contractions. A definite relationship was observed between the presence of severe decelerations (irrespective of the time relationship with any uterine contraction) and poor neonatal outcome. A relationship does exist between the presence of severe decelerations and flattening in the recording, which, as demonstrated in the previous part of the paper also exhibited a strong positive relationship with the neonatal outcome. When one considers the different degrees of flattening, it appears that a further correlation between decelerations and neonatal state is demonstrable only in the case of a 10--50% flat recording. Here the probability of a distressed baby is 20% in the absence of decelerations, but 43.4% in the presence of decelerations. In other cases (i.e., less than a 10% or more than a 50% flat recording) the pronostic significance of the instability of the record is not significantly modified by he presence or absence of decelerations. These results indicate that consideration of decelerations is only advisable in these cases where instability is moderately affected (flattening in 10-50% of the record) and that the use of the oxytocin challenge test OCT may be reserved for such cases, when these are neither spontaneous contractions nor decelerations and not contraindications present.