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Background
A detailed second trimester ultrasound examination (STU) is commonly performed to assess fetal anatomy, biometry and for evaluation of several other fetal and maternal indications. The American College of Radiology (ACR), the American Institute of Ultrasound in Medicine (AIUM), the American College of Obstetricians and Gynecologists (ACOG), the Society for Maternal Fetal Medicine (SMFM), and the Society of Radiologists in Ultrasound (SRU) have collaborated to establish minimum requirements for performing and interpreting a STU. Early identification of fetal anomalies through advancements in ultrasonography allow the patient adequate time to pursue diagnostic testing or genetic counseling. The STU is routine at 18 - 22 weeks' gestation in low-risk populations, or a detailed examination can be performed in women with a past medical history of diabetes mellitus, obesity, advanced maternal age, or a suspected fetal anomaly. Adherence to the current standard of care parameters increases the likelihood of detecting many fetal abnormalities with the lowest possible risk for the mother and fetus.

Educational Goals / Teaching Points
Describe scanning protocols for STU. Provide a comprehensive checklist for consistent and accurate interpretation of STU. Review normal imaging findings for STU comprehensive checklist. Demonstrate common pathologies encountered on STU. Understand appropriate follow up and recommendations for common pathologies.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Due to variability of fetal presentation and fetal motion, acquiring fetal measurements of a STU in a set order can be challenging and inefficient. Our institution utilizes several standardized practices to address these unique challenges. While acquiring images, our sonographers capture and label key elements of a STU in the order they are presented to them while using a checklist to confirm each required element has been obtained. Additionally, our sonographers document quality of visualization (not seen, suboptimal, normal, or free text a description). This information is made available to the interpreting radiologist who can make necessary changes at the time of interpretation. As an additional quality control measure, a dry erase marker and laminated reusable SSTUE checklist is available at radiology reading stations. This checklist allows radiologists to verify they have reviewed a complete examination and that no elements are missing.

Conclusion
The STU is routinely performed for evaluation of low-risk pregnancies and multiple other maternal and fetal anomalies. The AIUM–ACR–ACOG–SMFM–SRU collaboration has compiled a minimum set of standard elements that should be acquired for each STU. At our institution, key elements of a STU are presented and checklist systems are used to verify a complete examination.