Usefulness and timing of the third-trimester ultrasound scan: a review of guidelines and underlying evidence

There is a broad recognition of third-trimester ultrasound being useful for fetal monitoring, but consensus is lacking regarding its routine use in low-risk populations, its outcomes and timing. Major evidence supports ultrasound screening at 36-week gestation in low-risk pregnancies to predict fetal growth restriction, macrosomia, structural anomalies, complications due to placental abnormalities, pre-eclampsia and onset of labor. When preceded by effective risk stratification done earlier in pregnancy, this strategy may enhance pregnancy management potentially improving maternal-fetal outcomes.