VP37.09: Sequential analysis of uterine artery Doppler waveform in women at high‐risk of pre‐eclampsia undergoing low‐dose aspirin prophylaxis

Objectives:                                                                                                     Low-dose aspirin is not always effective when prescribed to women at increased risk of pre-eclampsia (PE). This study was designed to assess the feasibility of using sequential changes in uterine artery Doppler pulsatility indices (UAD-PI) between 1st and 2nd trimester scans for the detection of response to aspirin.      Methods:                                                                                                             A cohort study of 339 women at increased risk of PE was conducted in a single, large maternity unit in the UK, between 2017 and 2019. UAD examinations were performed during the routine 1st and 2nd trimester scans. Aspirin response was assessed by serum Thromboxane B2 (TbxB2) with a cut-off 10ng/mL, taken at the time of the 2nd trimester scan. All women were prescribed 75 mg of aspirin.  Results:                                                                                                            The aspirin response rate was 76.1%. While changes in UAD-PI were not associated with response, adherence (log OR 0.36, 95% CI 0.22-0.51. p < 0.01), age (log OR 0.073, 95% CI 0.019-0.13, p < 0.01) and parity (log OR -0.75, 95% CI -1.1 to -0.37, p < 0.01) demonstrated association. Secondary analysis related to the occurrence of PE revealed a negative association with changes in UAD-PI and level of TbxB2 and positive association with history of hypertensive disease in pregnancy and 1st trimester UAD-PI. Ethnicity, 1st trimester UAD-PI, pre-existent morbidity (medical history of chronic kidney disease, autoimmune disease, and Diabetes) and smoking were positively associated with early onset PE, while change in UAD-PI and parity were negatively associated with it. Conclusions:                                                                                            Although sequential UAD was not useful in prediction of aspirin response, it was valuable in likelihood prediction of PE, especially early onset of PE before 34 weeks of gestation.