From the Guidelines
Frequent fetal ultrasounds without medical indication are not recommended, as they should be used only when needed and for the shortest time necessary, following the principle of ALARA (As Low As Reasonably Achievable) to minimize potential harm. The potential harm from frequent ultrasounds comes from the energy that ultrasound waves transfer to tissues, which can cause slight heating and possibly create small gas pockets in fluids (cavitation) 1. While no definitive human studies have proven harm from diagnostic ultrasound, it is essential to use ultrasound judiciously. Standard prenatal care typically includes 1-2 ultrasounds for low-risk pregnancies: one in the first trimester to confirm pregnancy and establish due date, and possibly another at 18-22 weeks to check fetal anatomy. Additional ultrasounds are warranted only when medically indicated for specific concerns, such as suspected fetal growth restriction (FGR) or preeclampsia 1.
Medical Indications for Ultrasound
Some medical indications for ultrasound include:
- Suspected fetal growth restriction (FGR)
- Preeclampsia
- Abnormal fetal anatomy
- Multiple pregnancy
- Previous history of FGR or preeclampsia
Guidelines for Ultrasound Frequency
According to the guidelines, routine third-trimester ultrasound in low-risk women is not recommended 1. The frequency of ultrasound scans should be determined by the presence of medical indications, such as suspected FGR or preeclampsia. For example, in cases of confirmed preeclampsia, serial evaluation of fetal growth, amniotic fluid volume, and UA Doppler are recommended from 26 weeks’ gestation until birth, with fetal biometry assessed no more frequently than every 2 weeks 1.
Importance of Medical Necessity
It is crucial to discuss any concerns about ultrasound frequency with your healthcare provider, who can explain the medical necessity of any recommended scans. Commercial "keepsake" ultrasounds for non-medical purposes are discouraged by medical organizations. The principle of ALARA should be followed, and ultrasound should be used only when needed and for the shortest time necessary to minimize potential harm.