Doppler sonography of uterine arteries at 20-23 weeks: risk assessment of adverse pregnancy outcome by quantification of impedance and notch.

OBJECTIVE

To assess the diagnostic value of Doppler sonography of the uterine arteries (DSUA) at 20-23 gestational weeks as screening procedure in a low risk population.

PATIENTS AND METHODS

The study group consisted of 7508 singleton low-risk pregnancies. Doppler sonography of both uterine arteries was performed as routine part of anomaly scan. Impedance of both uterine arteries was registered using the mean PI of the two uterine arteries. In case of notch, "Notch-Index" was defined as (C-D)/C with D = post-systolic nadir and C = following zenith of the waveform. Outcome variables were placental abruption, pre-eclampsia, intrauterine growth retardation, intrauterine/neonatal death and preterm delivery before 32 completed gestational weeks. To discriminate normal and pathological waveform, incidence of adverse pregnancy outcome was related to four different definitions of pathological waveform. To describe the severity of impairment of perfusion, the frequency of adverse pregnancy outcome was related to different classes of impedance.

RESULTS

To find a simple discrimination between normal and pathological uterine perfusion, best diagnostic performance was reached by a definition using a combination of high impedance and notch (no notch and mean PI > P'95 or unilateral notch and mean PI > P'90 or bilateral notch and mean PI > P'50). The prevalence of notch in nulliparae (8.5%) was higher than in parae (4.7%) and decreased with increasing gestational age (20 weeks: 8.6%-23 weeks: 5.4%). We found a clear relation between elevation of impedance, depth of notch and frequency of adverse pregnancy outcome with a frequency of complications varying from 3.2% (mean PI < or = 0.8, mean NI = 0.1) to 38.4% (mean PI > 2.0, mean NI > 0.1).

CONCLUSION

Doppler sonography of the uterine arteries at 20-23 weeks has the capacity to predict at least a part of severe forms of adverse pregnancy outcome and to assess the probability of complications by quantification of the impairment of the uterine blood flow.