(749) Maternal Position Effects on Middle Cerebral Artery Pulsatility Index and Associated Adverse Pregnancy Outcome

Objective: We have previously demonstrated that maternal anatomical position changes directly affect the fetal middle cerebral artery (MCA) Doppler pulsatility indices (PI) and may serve as a predictor for adverse pregnancy outcomes. After power analysis of pilot data, we sought to determine if these PI changes were associated with adverse pregnancy outcomes.

Study Design: A prospective cohort study of pregnant people with a singleton, non-anomalous fetus, recruited between 18 and 24 weeks of gestation, in a single tertiary care center from 12/2021- 2/2022. MCA Dopplers were obtained and PI indices were measured and recorded, first in the supine position and then in the maternal left lateral position. Based on our prior findings suggesting a PI Δ of 0.22 being associated with adverse composite pregnancy outcomes (preeclampsia, fetal growth restriction and oligohydramnios), we divided the cohort into two groups, those above and below the cutoff of Δ =0.22. Demographic characteristics were compared using univariable analyses. Multivariable logistic regression was performed to compare the composite and individual pregnancy outcomes, adjusting for significant demographic differences between the groups.

Results: We recruited 228 patients and followed them to delivery. There were 107 that had a PI Δ < 0.22 and 121 that had PI Δ > 0.22. Demographics and outcomes are seen in Table 1. The primary outcome of composite adverse outcomes did not differ between the groups. However, among pregnancies with PI Δ < 0.22, preeclampsia was more likely to develop than pregnancies with PI Δ > 0.22 [aOR 95%CI 3.30 (1.02-10.69)].

Conclusion: We found that a second trimester fetal MCA PI Δ < 0.22 with maternal position changes at anatomy ultrasound was associated with developing preeclampsia. This data suggests that there may be an association of early decreased feto-placental reserve and the development of preeclampsia later in the pregnancy.