Doppler velocimetry of uterine and umbilical arteries during pregnancy

Objective: To study the pulsatility index (PI), resistance index (RI) and systolic/diastolic (S/D) ratio of the 'umbilical' and 'uterine' arteries during pregnancy. To determine the normal range (mean + 2SD) for the various indices in our population. To also determine the statistical significance (P-value) of these values by comparing them with the abnormal indices in pregnancies that developed pregnancy-induced hypertension (PIH), and small for gestational age (SGA) babies. To determine which artery 'umbilical vs. uterine' and which index PI vs. RI vs. S/D, serve as better indicators for bad maternal and perinatal outcome in PIH and SGA babies. To conclude whether a Doppler study can be an effective screening test. Materials and Methods: A total of 120 random pregnancies were screened at 20, 28 and 34 weeks of gestation. A color Doppler scanner with a carrier frequency of 3.5 MHz was used for studying the uterine and the umbilical arteries. Pregnancies with a normal outcome were used for calculating the normal range of various indices and for testing the specificity and negative predictive value (NPV) of the study. Those pregnancies with an abnormal outcome (PIH and SGA babies) were used for calculating the sensitivity and positive predictive value (PPV) of the study. Results: In normal pregnancies, the flow velocity waveforms (FVWs) showed a good diastolic flow and fall in indices as pregnancy progressed. A low diastolic flow and high indices characterized the pregnancies with abnormal outcomes. The uterine artery had a better sensitivity and specificity as compared to the umbilical artery. Among the various uterine waveform parameters, the diastolic notch had the highest sensitivity and specificity. Among the umbilical indices, the PI had the highest sensitivity and specificity. Conclusion: Doppler provides a non-invasive method of assessing the fetal and maternal circulation during pregnancy. Both uterine and umbilical arteries have a low sensitivity at 20 weeks and therefore cannot be used as a screening test.