Clinical Significance Of Intermittently Absent End-Diastolic Flow Of The Fetal Umbilical Artery On Perinatal And Neonatal Outcomes Zeynep Kayaoğlu Yıldırım, Gynecologist and Obstetrician, Perinatologist, İstanbul Başakşehir Çam ve Sakura City Hospital, Drkayaoglu@Hotmail.Com, Alperen İnce, MD, Obstetrics and Gynecology Medical Student, Başakşehir Çam ve Sakura City Hospital,Gökhan Bayanmelek, Gynecologist and Obstetrician, Perinatologist, İstanbul Başakşehir Çam ve Sakura City Hospital,Gökhan Bolluk, Gynecologist and Obstetrician, Perinatologist, Başakşehir Çam ve Sakura City Hospital

Doppler velocity measurement of the umbilical artery (UA) serves as a crucial clinical tool for monitoring feto-placental hemodynamics and assessing fetal well-being in high-risk pregnancies. This technique has demonstrated notable advantages in monitoring potentially risky fetuses, particularly in pregnancies complicated by placental disorders, such as fetal growth restriction (FGR). Since UA Doppler (UAD) results can deteriorate over the course of pregnancy, regular assessments are recommended. However, the frequency of these assessments, management protocols, and delivery timing recommendations vary among major national obstetric societies.

The UA blood velocity waveform is typically characterized by the pulsatility index (PI) and qualitative information concerning the potential absence or reversal of end-diastolic flow (EDF). Absent end-diastolic flow (AEDF) signifies increased resistance to flow in the placental vascular bed and is associated with elevated risks of intrauterine death and adverse perinatal outcomes. AEDF in the UA can be either persistent (pAEDF), occurring in most or all fetal cardiac cycles, or intermittent (iAEDF), manifesting in only some of the cardiac cycles. However, standardized definitions for these terms lack and the clinical implications of the iAEDF versus the pAEDF remain unclear.

A previous study indicated that, compared to fetuses with pAEDF, those with iAEDF are diagnosed with UAD abnormalities later in pregnancy and are delivered at a later gestational age (GA) with higher birth weights. Consequently, it is plausible that some fetuses with an iAEDF may remain in utero for an extended duration without facing an immediate risk of death. Identifying this specific subgroup might allow the avoidance of some neonatal risks associated with extremely preterm birth.

In this study, we aimed to assess the risk of adverse perinatal outcomes among pregnant patients with intermittently absent and persistently absent end-diastolic umbilical artery flow. This investigation seeks to contribute to a better understanding of the fetal risks associated with different patterns of absent end-diastolic flow, thereby informing clinical management and decision-making for high-risk pregnancies.

We performed a retrospective cohort study of patients with non-anomalous, singleton pregnancies diagnosed with intermittent absence of end-diastolic umbilical artery Doppler flow or persistent absence of end-diastolic flow at our institution from 2020 to 2023. The study was approved by the Başakşehir Çam ve Sakura City Hospital Clinical Research Ethics Committee (ethics no.2023-561, date 08/11/2023) and was conducted in accordance with the latest version of the Declaration of Helsinki (2019/92). Fetuses were classified into two categories: intermittent absent end-diastolic flow and persistent absent end-diastolic flow.