Point‐Of‐Care Ultrasound for the Assessment of the Cerebroplacental Ratio in Near‐Term Pregnancies: An Agreement Study With Conventional Ultrasound

OBJECTIVES: The cerebroplacental ratio (CPR) is associated with perinatal mortality and morbidity, and its measurement has been proposed in uncomplicated pregnancies near term to identify fetuses at risk of adverse outcome. A major limitation to its widespread adoption is the lack of ultrasound equipment dedicated to antepartum clinics. Point-of-care ultrasound (POCUS) has emerged as an affordable bedside tool that may overcome this limitation, but no comparative studies between POCUS and conventional ultrasound systems have been conducted for the evaluation of CPR. Our aim was to assess the level of agreement between these two devices in the evaluation of CPR. METHODS: In a prospective cross-sectional study we examined singleton pregnancies between 36 and 38 weeks of gestation. In half of the participants the acquisition was repeated a second time by the same operator on the same device in order to quantify intra-observer reproducibility. Two observers performed Doppler recordings in a randomized sequence, each blinded to the other's results, one using a handheld ultrasound device (POCUS; Q7, Esaote, Genoa, Italy) and the other a conventional ultrasound system (MyLab Omega, Esaote, Genoa, Italy). Doppler waveforms were acquired in the absence of fetal movements and during maternal apnoea. The umbilical artery pulsatility index (UA PI) and the middle cerebral artery PI (MCA PI) were measured and the CPR was calculated as MCA PI/UA PI. A third obstetrician, blinded to the device and to the operator, assessed the quality of the recordings, assigning a score from 0 to 3 for both image quality (IQS) and measurement quality (MQS). Agreement was quantified with the intraclass correlation coefficient (ICC) and the Bland-Altman method. RESULTS: Eighty women participated in the study. Mean values did not differ between conventional ultrasound and POCUS for UA PI (1.04 ± 0.17 vs. 1.04 ± 0.20, p = 0.760), MCA PI (1.63 ± 0.22 vs. 1.65 ± 0.26, p = 0.113) or CPR (1.61 ± 0.34 vs. 1.65 ± 0.42, p = 0.137). The ICC between the two devices was 0.89 (95% CI 0.83-0.93) for UA PI, 0.85 (95% CI 0.78-0.90) for MCA PI and 0.84 (95% CI 0.77-0.90) for CPR. Bland-Altman analysis showed a negligible bias, with limits of agreement ranging from -0.45 to +0.38 for the CPR. Intra-observer reproducibility, assessed on two consecutive recordings in 40 of these women, yielded an ICC of 0.90 (95% CI 0.82-0.95) for UA PI, 0.85 (95% CI 0.73-0.92) for MCA PI and 0.85 (95% CI 0.74-0.92) for CPR, with no difference in within-subject variability between the two devices. There were no significant differences between conventional ultrasound and POCUS in IQS for UA PI (2.45 vs. 2.52, p = 0.343) or MCA PI (2.41 vs. 2.30, p = 0.214), nor in MQS for UA PI (2.42 vs. 2.36, p = 0.466) or MCA PI (2.42 vs. 2.23, p = 0.083). CONCLUSIONS: POCUS and conventional ultrasound showed good agreement in the evaluation of the CPR at near term, with no systematic difference between devices and comparable image and measurement quality. The agreement between devices was of the same order as the intra-observer repeatability of the measurement itself, indicating that most of the observed discrepancy reflects the intrinsic variability of fetal Doppler rather than the handheld device. POCUS appears to be a reliable and affordable alternative for the assessment of fetal Doppler in the antenatal clinic.