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Am Fam Physician. 2022;105(5):540-541

Author disclosure: No relevant financial relationships.

Clinical Question

Does performing dating ultrasonography before a first-trimester uterine evacuation improve outcomes or safety?

Evidence-Based Answer

No. Routine use of ultrasonography before a first-trimester abortion is not necessary. (Strength of Recommendation: B, systematic reviews and retrospective cohort studies.) In patients seeking medical or surgical abortion in the first trimester, date of the last menstrual period (LMP) alone can appropriately determine gestational age for treatment (before 63 to 90 days' gestation) in 93.8% to 97.6% of patients. Bimanual examination and LMP together accurately determine candidacy for treatment in 98.4% of patients. Ultrasonography does not appear to affect the rate of missed ectopic pregnancies or reduce incomplete abortions or ongoing pregnancy rates.

Evidence Summary

ULTRASONOGRAPHY ADDS LITTLE TO DECISION-MAKING

Two large cohort trials compared LMP and bimanual examination to ultrasonography for estimation of gestational age in patients presenting for pregnancy termination. A prospective cohort trial (n = 4,484) enrolled pregnant patients in the United States who were seeking pregnancy termination with a suspected gestational age of less than 63 days (treatment date cutoff) based on LMP.1 Patients who had previous ultrasonography or suspected molar or ectopic pregnancies were excluded. All patients underwent bimanual examination and ultrasonography to confirm gestational age at the time of enrollment. The primary outcome was whether patients with pregnancies greater than 63 to 78 days' gestation would be inappropriately offered medical abortion if LMP alone or LMP plus bimanual examination were used to date the pregnancies compared with using ultrasonography. A certain LMP alone was able to accurately determine candidacy for treatment in 97.6% of patients compared with ultrasonography. LMP plus bimanual examination together accurately determined candidacy for treatment in 98.4% of patients vs. ultrasonography. Approximately 59 sonograms would need to be performed to correctly determine candidacy for medical abortion (based on gestational age) for one additional patient compared with LMP plus bimanual examination.

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Clinical Inquiries provides answers to questions submitted by practicing family physicians to the Family Physicians Inquiries Network (FPIN). Members of the network select questions based on their relevance to family medicine. Answers are drawn from an approved set of evidence-based resources and undergo peer review. The strength of recommendations and the level of evidence for individual studies are rated using criteria developed by the Evidence-Based Medicine Working Group (https://www.cebm.net).

The complete database of evidence-based questions and answers is copyrighted by FPIN. If interested in submitting questions or writing answers for this series, go to https://www.fpin.org or email: questions@fpin.org.

This series is coordinated by John E. Delzell Jr., MD, MSPH, associate medical editor.

A collection of FPIN’s Clinical Inquiries published in AFP is available at https://www.aafp.org/afp/fpin.

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