Validity of antenatal diagnosis of intrauterine growth restriction by umbilical Doppler waveform index

Objective: To evaluate the validity of systolic/diastolic (S/D) ratio of the umbilical artery in predicting intrauterine growth restriction (IUGR). Study Design: Diagnostic test study. Setting: Maharaj Nakorn Chiang Mai Hospital, Chiang Mai University. Subjects: Two hundred and twelve singleton pregnancies between 30 and 42 weeks' gestation with clinical suspicion of IUGR were recruited and followed-up between December 1^st 1995 and June 30^th 1998. They were sonographically examined for routine fetal biometry and S/D ratio of umbilical artery Doppler waveform measurement within 14 days of delivery. All of them had an accurate date of last menstrual period and were between 30-42 weeks' gestation. Material and Method: The umbilical artery S/D ratio was obtained by the same experienced sonographer, using the same ultrasound machine, Aloka 680EX, (Tokyo, Japan). The S/D ratio of 3 or greater was considered abnormal, predicting IUGR prenatally for every gestational week. IUGR was defined as low birth weight of less than the 10 ^th percentile of the standard birth weight curve of Maharaj Nakorn Chiang Mai Hospital. Main Outcome Measures: sensitivity, specificity, positive predictive value and negative predictive value. Results: The prevalence of IUGR among the study group was 50.9%. The S/D ratio of 3 or greater for predicting of IUGR gave the sensitivity, specificity, positive predictive value, and negative predictive value of 52.96%, 78.85%, 74.42% and 65.08%, respectively. Conclusion: The umbilical artery S/D ratio has relatively low sensitivity and is not a suitable test for IUGR screening. However, the specificity is rather high and it may be helpful in combination with other parameters.