Definition: A Limited Obstetrical ultrasound is performed to answer a specific, acute clinical question, when an immediate impact on management is anticipated, and when time or other constraints make performance of even a Basic sonogram impractical.

If a Limited Obstetrical ultrasound is performed on a woman who has not previously had a Basic or Targeted ultrasound examination, a follow-up Basic sonogram should be obtained, where appropriate. In patients who require serial sonograms and have already had a basic or targeted scan, some will only need Limited scans, while others will require Basic or Targeted scans. Clinical judgment should be used to determine the proper type of sonogram to perform, and the appropriate frequency.

Background: Professional groups with interests in obstetrical sonography including the American Institute of Ultrasound in Medicine (AIUM), the American College of Obstetricians & Gynecologists (ACOG), and the American College of Radiology (ACR) have proposed guidelines and standards for Basic obstetrical sonography. More advanced sonograms ("Targeted", or "Comprehensive") are also common for patients with identified risk factors for fetal anomalies or other complications. "Basic sonogram" is used here according to the AIUM Standards for the Performance of the Antepartum Obstetrical Ultrasound Examination. The terms Level I and Level II are obsolete, and their usage is discouraged.

The clinical practice of obstetrics can produce situations when even a basic sonogram is either impractical, or unnecessary and a "Limited" Obstetrical ultrasound is more appropriate. In addressing "Limited Sonograms" this document assumes that: Obstetrical ultrasound is only obtained when clinically important information is required.

When possible a Basic sonogram is more desirable than a Limited sonogram. If a Basic sonogram has not previously been obtained, it should be if the clinical situation permits.

The maximum available information should be obtained from every Obstetrical ultrasound.

Obstetrical ultrasound is not being used for entertainment, or for sex determination purposes in the absence of an indication. Obstetrical ultrasound is not being used solely for billing purposes.

A Limited sonogram is not a replacement for a Basic sonogram due to inexperience or lack of qualifications of the sonographer/sonologist.

Documentation: Limited sonograms require documentation. Whenever feasible, images should be stored as part of the medical record. Whether or not images are obtained, a full description of the findings is required. When a patient undergoes a Limited sonogram, it is important that she understands why a Limited scan is being done and that she has appropriate expectations about the information being sought. In particular, she should be aware that fetal anomalies may not be detected.

This document is not intended to provide a formal definition of limited sonogram for coding and billing purposes.

A Limited sonogram will rarely be appropriate in routine patient care. Generally, follow-up with more extensive sonography, either Basic or Targeted, should be performed when appropriate. In these cases, those managing the patient should carefully consider whether the Limited sonogram is necessary, or whether it will only add to the cost of care. If the latter is true, deferring the sonogram for a few hours until a more thorough assessment can be obtained may be prudent. The decision whether to perform a Limited scan must take into account whether a previous sonogram has been performed, and how long ago.