Clinical significance of umbilical artery intermittent vs persistent absent end-diastolic velocity in growth-restricted fetuses

Abstract

Umbilical artery absent end-diastolic velocity indicates increased placental resistance and is associated with increased risk of perinatal demise and neonatal morbidity in fetal growth restriction. However, the clinical implications of intermittent vs persistent absent end-diastolic velocity are unclear. We compared umbilical artery Doppler velocimetry changes during pregnancy and neonatal outcomes between pregnancies with fetal growth restriction and intermittent absent end-diastolic velocity and those with persistent absent end-diastolic velocity. In this retrospective study of singletons with fetal growth restriction and absent end-diastolic velocity, umbilical artery Doppler abnormalities were classified as follows: intermittent absent end-diastolic velocity (<50% of cardiac cycles with absent end-diastolic velocity) and persistent absent end-diastolic velocity (≥50% of cardiac cycles with absent end-diastolic velocity). The primary outcome was umbilical artery Doppler progression to reversed end-diastolic velocity. Secondary outcomes included sustained umbilical artery Doppler improvement, latency to delivery, gestational age at delivery, neonatal morbidity composite, rates of neonatal intensive care unit admission, and length of neonatal intensive care unit stay. Outcomes were compared between intermittent absent end-diastolic velocity and persistent absent end-diastolic velocity. Multivariate logistic regression was used to adjust for confounders. A receiver operating characteristic curve was generated to assess the sensitivity and specificity of the percentage of waveforms with absent end-diastolic velocity in predicting the neonatal composite. The Youden index was used to calculate the optimal absent end-diastolic velocity percentage cut-point for predicting the neonatal composite. Of the 77 patients included, 38 had intermittent absent end-diastolic velocity and 39 had persistent absent end-diastolic velocity. Maternal characteristics, including age, parity, and preexisting conditions did not differ significantly between the 2 groups. Progression to reversed end-diastolic velocity was less common in intermittent absent end-diastolic velocity than in persistent absent end-diastolic velocity (7.9% vs 25.6%; odds ratio, 0.25; 95% confidence interval, 0.06-0.99). Sustained umbilical artery Doppler improvement was more common in intermittent absent end-diastolic velocity than in persistent absent end-diastolic velocity (50.0% vs 10.3%; odds ratio, 8.75; 95% confidence interval, 2.60-29.5). Pregnancies with intermittent absent end-diastolic velocity had longer latency to delivery than those with persistent absent end-diastolic velocity (11 vs 3 days; P<.01), and later gestational age at delivery (33.9 vs 28.7 weeks; P<.01). Composite neonatal morbidity was less common in the intermittent absent end-diastolic velocity group (55.3% vs 92.3%; P<.01). Neonatal death occurred in 7.9% of intermittent absent end-diastolic velocity cases and 33.3% of persistent absent end-diastolic velocity cases (P<.01). The differences in neonatal outcomes were no longer significant when controlling for gestational age at delivery. The percentage of cardiac cycles with absent end-diastolic velocity was a modest predictor of neonatal morbidity, with an area under the receiver operating characteristic curve of 0.71 (95% confidence interval, 0.58-0.84). The optimal percentage cut-point for fetal cardiac cycles with absent end-diastolic velocity observed at the sentinel ultrasound for predicting neonatal morbidity was calculated to be 47.7%, with a sensitivity of 65% and specificity of 85%. Compared with persistent absent end-diastolic velocity, diagnosis of intermittent absent end-diastolic velocity in the setting of fetal growth restriction is associated with lower rates of progression to reversed end-diastolic velocity, higher likelihood of umbilical artery Doppler improvement, longer latency to delivery, and higher gestational age at delivery, leading to lower rates of neonatal morbidity and death. Our data support using an absent end-diastolic velocity percentage cut-point in 50% of cardiac cycles to differentiate intermittent absent end-diastolic velocity from persistent absent end-diastolic velocity. This differentiation in growth-restricted fetuses with absent end-diastolic velocity may allow further risk stratification.