Key Message
No relevant evidence was identified comparing the safety of frequent obstetrical ultrasounds compared to the routine use of obstetrical ultrasound during pregnancy. This review identified 10 evidence-based guidelines that provided recommendations regarding various indications for obstetrical ultrasound, as well as the frequency of obstetrical ultrasound; however, the methodological rigour of these guidelines is limited and recommendations should be interpreted with caution. One guideline recommended against obstetrical ultrasound for non-medical purposes and recommended that ultrasound exposure be as low as reasonably possible during pregnancy. These recommendations were based on moderate-quality evidence and expert opinion, and should be interpreted with caution. The guidelines made recommendations for specific patient populations for whom more frequent obstetrical ultrasound examinations may be required. These populations included pregnancies affected by certain congenital infections, people pregnant with twins, pregnant adolescents, and pregnant people at high risk for fetal anomalies or for whom mid-trimester transabdominal ultrasound would be challenging.