Fetal acoustic stimulation in early labour: a screening test for candidates of continuous FHR monitoring in low risk parturients

ABSTRACT

This work was done to investigate the value of fetal acoustic stimulation test in early labour as a predictor of fetal outcome and its usefulness as a screening test. One hundred and sixty four low risk parturients, with a singleton fetus in cephalic presentation, gestational age 37 - 41 weeks and in latent phase of labour with cervical dilatation less than 4cm were screened by the admission test for 20 minutes followed by fetal acoustic stimulation test. Abnormal response to fetal acoustic stimulation test [type II and III] was observed in 3.35% after reactive admission test and in 11.1% after equivocal admission test compared to 66.7% after ominous admission test [P < 0.001, < 0.05 respectively]. The incidence of fetal distress after reactive admission test and normal fetal acoustic stimulation test [type IA and IB] was 1.4% compared to 20% with reactive admission test and abnormal fetal acoustic stimulation [P < 0.01]. Equivocal or ominous admission test with normal fetal acoustic stimulation was associated with 10% incidence of fetal distress compared to 60% with equivocal or ominous admission test and abnormal fetal acoustic stimulation [P < 0.05]. The negative predictive value of fetal acoustic stimulation test was 98.1% and its positive predictive value was 40% compared to 26.7% for admission test. Fetal acoustic stimulation test in early labour appears to be a valuable screening test to label parturients for low, or high, risk category for intrapaturn fetal distress. In addition the test overcomes the problems of interpretation of equivocal traces