Routine Third Trimester Sonogram: Friend or Foe.

Several risk factors for adverse pregnancy outcomes can be identified by a routine third trimester ultrasound scan. However, there is also potential for harm, anxiety, and additional health care costs through unnecessary intervention due to false positive results. The evidence base informing the balance of risks and benefits of universal screening is inadequate to fully inform decision making. However, data on the diagnostic effectiveness of universal ultrasound suggest that better methods are required to result in net benefit, with the exception of screening for presentation near term, where a clinical and economic case can be made for its implementation.