Addressing Pitfalls in the Study of Discrepant Umbilical Artery Dopplers.

We thank Drs Dall’Asta et al for their interest and comments on our study. We agree with their assessment that discordant umbilical artery (UA) Doppler findings can potentially impact fetal growth restriction (FGR) surveillance and management. The challenge of reproducibility of the UA pulsatility index (PI), as described in their letter, will likely remain a challenge if only 1 of the paired UAs is sampled given the inability to know if the same vessel is repeatedly sampled. In practice, we find sampling both arteries to be quite straightforward if a long segment of the cord is visualized with color Doppler, which allows the 2 arteries to be seen running side by side as noted in Figure 1 of our manuscript.1Steller J.G. Driver C. Gumina D. et al.Doppler velocimetry discordance between paired umbilical artery vessels and clinical implications in fetal growth restriction.Am J Obstet Gynecol. 2022; 227: 285.e1-285.e7Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar The points made regarding the size of the UA and the correlation with placental pathology are well taken. We can measure diameters from paired UAs retrospectively from cross-sectional umbilical cord segment images in a similar study population in which we assessed umbilical vein dimensions and flow.2Hamidi O.P. Driver C. Steller J.G. et al.Umbilical venous volume flow in late-onset fetal growth restriction.J Ultrasound Med. 2023; 42: 173-183Crossref PubMed Scopus (1) Google Scholar Access to placentas for examination was limited because the majority of late-onset FGR pregnancies referred to our center delivered at out-lying community hospitals. We also agree that different nomograms will lead to different diagnostic assignments of risk. We chose a well-described UA nomogram used in our clinic population for years. Given that the fetal biophysical state influences UA Doppler recordings, we always try to obtain recordings in a state of rest, and in our population, there were no biophysical profile scores suggesting risk for acidemia. We fully appreciate the comments in the final paragraph of their letter. We did not encounter absent end diastolic flow in our study population, a finding primarily seen in early-onset FGR.3Lees C.C. Stampalija T. Baschat A. et al.ISUOG Practice Guidelines: diagnosis and management of small-for-gestational-age fetus and fetal growth restriction.Ultrasound Obstet Gynecol. 2020; 56: 298-312Crossref PubMed Scopus (256) Google Scholar The clinical implications of discordant UAs that they list are important to acknowledge, including the impact on the diagnosis of FGR, frequency of monitoring, delivery timing, and the importance of repeated measures with and without placental disease progression. For more than 2 decades, clinical trials and management of FGR have been based on sampling a single UA vessel at random. We agree with their cautionary statement and would again emphasize that with either repeated sampling during a single examination or serial samplings over time, one will never know if they are sampling the same UA or not unless both arteries are sampled. Furthermore, in situations in which the PI is the final arbiter in the diagnosis or management of FGR, little would be lost by using the worst PI, which could always be reversed by the results of future serial examinations. Prospective studies determining the clinical impact of sampling both umbilical arteries in early- and late-onset FGR are needed. We acknowledge our other coauthors on our original manuscript: Camille Driver, MA, Diane Gumina, PhD, Emma Peek, BS, and Teresa Harper, MD, as well as Allison Gillan, BS, Sherry Bumford, RDMS, and Lindsey Herlands, RDMS, who assisted with collecting waveform information. These individuals worked at the John C. Hobbins Perinatal Center in Denver, CO, and have no other financial disclosures or conflict of interest. Umbilical artery Doppler velocimetry in fetal growth restriction: evidence and unanswered questionsAmerican Journal of Obstetrics & GynecologyVol. 229Issue 2PreviewSteller et al1 reports that in a cohort of babies with intrauterine growth restriction (IUGR) the mean difference in the umbilical artery (UA) pulsatility index (PI) between each UA was 11.7%, and in 16.7% there was discordance in categorization between 1 normal and 1 abnormal Doppler recording. Overall, over 1 in 2 fetuses with an abnormal UA PI showed discordant results between the 2 umbilical arteries, and in these cases the outcome was intermediate with respect to IUGR fetuses showing both normal or both abnormal UA PI. Full-Text PDF