Ultrasound time domain and color M‐mode analysis of uterine blood flow in twin pregnancy: prediction of uteroplacental complications, placental insufficiency and intrauterine growth restriction

Objectives:  A preliminary assessment of the usefulness of a non-Doppler technique of uterine artery blood flow measurement in twin pregnancy, for the prediction of preeclampsia, utero-placental insufficiency and intrauterine growth restriction. To compare the results obtained with the contemporary Doppler method. Methods:  A prospective study of 32 twin pregnancies presenting consecutively for a routine second trimester ultrasound scan. Maternal demographic and physical characteristics were recorded in all cases. Using previously described methods, blood flow studies were then conducted using the two different techniques; pulsed color Doppler was used to measure blood flow velocity waveform resistance indices, while a time domain correlation technique with color M-mode imaging was used to measure blood volume flow in both uterine arteries. The placental site and morphology, uterine artery waveform characteristics, and presence or absence of diastolic notches were recorded. The ultrasound fetal growth measurements were plotted on reference charts to assess individual fetal growth patterns, and the obstetric outcomes were recorded for all the pregnancies. Statistical analysis was performed to assess the predictive value of each method of blood flow measurement for the relevant obstetric complications. Exclusions:  One mother with sickle cell trait (Hb A + S). Results:  An abnormal uterine artery waveform (high resistance with persistence of uterine artery notching) was of limited value in the prediction of pre-eclampsia and IUGR in twin pregnancies. There was close correlation between a significant reduction in uterine artery blood volume flow and early onset intrauterine growth restriction requiring delivery before 34 weeks gestation. Uterine artery blood volume flow may be less influenced by the placental site compared with traditionally used resistance and pulsatility indices. Conclusions:  Uterine artery notching appears to be of limited value in the direct prediction of growth complications in twins. The volume flow method correctly identified all the pregnancies complicated by early onset intrauterine growth restriction. Both methods may well prove to be complementary in the antenatal management of twin pregnancy although further studies will be required.