Different types of variable decelerations and their effects to neonatal outcome

Although the only objective finding of intrapartum fetal distress is obtained through the measurement the fetal scalp pH, this invasive procedure is not available in every institution. The careful examination of fetal heart rate tracings for abnormalities, especially of the most commonly seen one, variable decelerations gains great importance under these circumstances. The aim of the present study is to determine the prognostic significance of variable decelerations in intrapartum fetal heart rate monitoring.

A total of 96 fetal heart rate tracings were analysed to assess the prognostic significance of variable decelerations. Sixty-six percent (64/96) of cases exhibited atypia characterised with (1) slow return of the fetal heart rate to the baseline; (2) loss of variability during the decelerations; (3) loss of initial and/or secondary accelerations; (4) persistence of secondary acceleration (overshoot); and (5) continuation of the baseline fetal heart rate at a lower level; (6) biphasic deceleration. One and five-minute Apgar scores and umbilical artery pH were used to assess the final fetal condition.

Adverse fetal outcome characterised by fetal acidosis and Apgar score lower than 7 at one and five minutes were uncommon with pure variable decelerations. Typical and atypical variable decelerations were associated with low Apgar scores (< 7) at one minute in 9.3% and 54.6% of cases (p < 0.001) and at five minutes in 6.25% and 25% of cases (p < 0.05), respectively. In addition umbilical artery pH found to be lower than 7.2 in these cases ( 18.75% - p < 0.05). There was no danger for the fetal haemodynamic conditions when typical uterus contraction/variable deceleration ratios were two or more than two. However, risk of fetal hypoxia damage was quite high when this ratio was lower than two in atypical variable 5th minute low Apgar scores and pH (81.8% and 36.6% respectively). Atypical features are helpful in the identification of distress characterised by low Apgar scores in fetuses with variable decelerations. Admission to the neonatal intensive care unit was more common in patients with atypical variable decelerations in comparison with typical variable decelerations (34.3% versus 3.1%).

While typical variable decelerations are frequently harmless, atypical variations pose a significant risk of fetal hypoxia.