Relations between fetal brain-sparing circulation, oxytocin challenge test, mode of delivery and fetal outcome in growth-restricted term fetuses

Abstract

Objective: The study was designed as a prospective non-interventional, observational study to elucidate the potential value of fetal middle cerebral artery Doppler velocimetry to identify brain-sparing flow in a surveillance program for suspected intrauterine growth restriction (IUGR).

Material and methods: The study was carried out at Skåne University Hospital, Malmö, Sweden. One hundred and twenty-six single pregnancies suspected of IUGR at ≥36 gestational weeks were assessed. The main outcome measures were positive/negative oxytocin challenge test (OCT) and cesarean/vaginal delivery. The pregnancies were managed with ultrasound fetometry, uterine and umbilical artery Doppler flow velocimetry, nonstress test, and an OCT to decide the optimal time and mode of delivery. Cases with a positive OCT were promptly delivered by cesarean section, whereas negative cases were allowed a trial of labor. Middle cerebral artery Doppler flow velocimetry results were blinded to the managing obstetricians. Brain-sparing flow was defined as a middle cerebral artery-to-umbilical artery pulsatility index ratio of <1.08. Nonparametric statistics with significance set at p < 0.05 were used, and Cohen's kappa coefficient was calculated for congruence of brain-sparing flow with OCT and mode of delivery, respectively.

Results: The positive predictive value and sensitivity figures of brain-sparing flow to indicate a positive OCT and cesarean delivery were 33-63%. The inter-rater reliability of brain-sparing flow vs. positive OCT showed a kappa coefficient of 0.19, and brain-sparing flow vs. cesarean section among OCT-negative cases a kappa coefficient of 0.23.

Conclusion: Fetal brain-sparing flow is a poor predictor of a positive OCT, and of cesarean section in OCT-negative cases.