EP17.49: The role of second trimester uterine artery Doppler using uterine artery score in routine prenatal care in Switzerland

The role of second trimester uterine artery Doppler (UtAd) is unclear and since there is no clear recommendation in the guidelines, its implementation varies greatly. The DEGUM mentions “uterine artery score (UAS)”, a score combining PI and notching in both UtA (1 point each for PI >1.2 and notch, range 0-4), as a possible tool to determine surveillance intervals in high-risk pregnancies. However, it is unclear how to proceed with low-risk pregnancies. The aim of this study is to determine whether second trimester UtAd interpreted with UAS is useful in an unselected Swiss population. We retrospectively calculated the UAS in all singleton pregnancies with second trimester scan at 20-24 weeks between 09/21 and 08/23 and delivery in our department and analysed its relationship with perinatal outcome. We included a total of 503 women. 38.4% had a UAS of 0, 27.8% of 1, 20.7% of 2, 8.7% of 3 and 4.4% of 4. In UAS 3+4 there were significant more women with autoimmune disease and abnormal PE screening. Other characteristics were similar between the groups. With UAS >2 there was a significant increase in adverse perinatal outcome such as hypertension/PE (OR 7.87, 95% CI 3.37-18.39), SGA <P10 (OR 6.83, 95% CI 3.76-12.38) and preterm birth (OR 4.85, 95% CI 2.4-9.79). In contrast, no significant difference was found when comparing UAS 0, 1 and 2. In general, NPV for adverse outcomes were high while PPV were low. In 50% of SGA-fetuses in UAS 3+4, the woman had no risk factor. Routine second trimester UtAd is useful in all pregnancies as it can identify additional patients without a pre-existing risk and with normal PE screening who generally would not be eligible for intense surveillance, but still develop SGA later. Further, due to the high NPV of normal UtAd, it qualifies as a rule-out tool for PE and SGA even in high-risk pregnancies. UAS is an effective tool for interpretation of UtAd. The cut-off should be set at 2. In case of UAS 3 or 4 a more intense surveillance program should be offered.