Objective: To review the benefits of and requirements for a complete second trimester ultrasound and the documentation needed.
Outcomes: A complete second trimester ultrasound provides information about the number of fetuses, the gestational age, the location of the placenta, and fetal and maternal anatomy.
Evidence: In the production of this document, the American Institute of Ultrasound in Medicine's "Practice Guideline for the Performance of Obstetric Ultrasound Examinations," the American College of Obstetricians and Gynecologists' practice bulletin, "Ultrasound in Pregnancy," and the Royal College of Obstetricians and Gynaecologists' Working Party Report, "Ultrasound Screening" were reviewed. PubMed and the Cochrane Database were searched using the words "routine second trimester obstetrical ultrasound."
Values: The evidence was evaluated using the guidelines developed by the Canadian Task Force on Preventive Health Care.
Benefits, harms, and costs: A routine complete second trimester ultrasound between 18 and 22 weeks and a complete ultrasound report will provide the best opportunity to diagnose fetal anomalies and to assist in the management of prenatal care. It will also reduce the number of ultrasound examinations done during the second trimester for completion of fetal anatomy survey. The costs are those involved with the performance of obstetrical ultrasound.
Validation: This is a revision of previous guidelines; information from other consensus reviews from medical publications has been used.
Sponsors: The Society of Obstetricians and Gynaecologists of Canada.
Recommendations: 1. Pregnant women should be offered a routine second trimester ultrasound between 18 and 22 weeks' gestation. (II-2B) 2. Second trimester ultrasound should screen for the number of fetuses, the gestational age, and the location of the placenta. (II-1A) 3. Second trimester ultrasound should screen for fetal anomalies. (II-2B).