Prediction of fetal acidaemia in intrauterine growth retardation: comparison of quantified fetal activity with biophysical profile score

OBJECTIVE: To study the relation between quantified fetal movements and fetal activity assessed by the biophysical profile score and the pH in umbilical arterial blood at elective caesarean section. DESIGN: Fetal activity was assessed within 24 h prior to caesarean section for decelerative fetal heart rate patterns both by quantification (% of time spent moving) and by applying the biophysical profile score (BPS) criteria. SETTING: Department of Obstetrics, University Hospital. SUBJECTS: Nineteen growth retarded fetuses. MAIN OUTCOME MEASURES: Fetal generalised movements (FGM%), fetal breathing movements (FBM%), total fetal activity (TFA% = FGM% + FBM%); FGM, FBM and tone as assessed according the biophysical profile score (BPS); umbilical arterial pH. RESULTS: In all 11 acidaemic fetuses (pH < 7.20) TFA% was below the 10th centile for normal fetuses; nine had decreased FGM% and eight decreased FBM%. Absence of FGM or tone according to the biophysical profile score was only seen in two acidaemic fetuses. CONCLUSION: TFA% < 11.7% was a better predictor of acidaemia at birth than either reduced FGM%, FBM%, or absence of FGM, FBM and tone as defined in the biophysical profile score. The two methods of assessing FBM were identical in predicting acidaemia, suggesting that in presence of acidaemia the decrease of FBM may be an all-or-none phenomenon. Furthermore, the data indicate that reduction in body movements may precede reduction in breathing movements.