Extent of absent end‐diastolic flow in umbilical artery and outcome of pregnancy

Abstract

Objectives To investigate if the extension of absent end‐diastolic flow (AEDF) in the umbilical artery (UA) Doppler velocimetry predicts outcome of pregnancies. Methods This was a retrospective observational study based on the background material of 25,000 Doppler examinations of UA flow between 1998 and 2017 at the Blood Flow Laboratory, Level III Perinatal Center, Lund, Sweden. All pregnancies with AEDF in UA were identified and the duration of AEDF in proportion to the total duration of heart cycle (T_a/T_tot ratio) was measured in the digital images of Doppler spectrum recorded at the last examination before delivery. Clinical data on pregnancies and neonatal outcomes were extracted from the Regional Perinatal Database and the hospital patient records. Results A total of 170 fetuses (122 [72%] singletons and 48 [28%] twins) were included in the study. Median gestational age at birth was 189.5 (range 163‐279) days, i.e. 27+0 (23+2 ‐ 39+6) weeks+days, birthweight 650 (320‐3326) g, and deviation from expected birthweight ‐2.975 (‐6.38 to 0.69) standard deviation score (SDS). There were 15 (9%) intrauterine and 17 (10%) neonatal deaths. The Doppler velocimetry results did not fundamentally differ between singletons and twins, giving rationale to the use of T_a/T_tot ratio in the total study group. The mean T_a/T_tot ratio was 0.42 (SD 0.08) and 0.34 (0.08) among stillborn and liveborn fetuses, respectively (p=0.002). For fetuses examined before 30 gestational weeks, a cut‐off at T_a/T_tot ratio 0.30 predicted intrauterine death with 92% sensitivity and 98% negative predictive value (NPV) (area under ROC curve [AUC] 0.74) and any death with 83% sensitivity and 85% NPV (AUC 0.66). Conclusions In fetuses with AEDF in UA, the extension of absent flow exceeding 30% of the total heart cycle length might predict the risk for fetal demise, even before 30 weeks, and possibly, facilitate the obstetric decision‐making and outcome.