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Study Evaluates Assessing Gestational Age Via Last Menstrual Period for Medical Abortion

Study Evaluates Assessing Gestational Age Via Last Menstrual Period for Medical Abortion

May 29, 2015 —Summary of "Early Medical Abortion Without Prior Ultrasound," Raymond/Bracken, Contraception, April 17, 2015.

"A recently published systematic review concluded that use of ultrasound to determine gestational age (GA) before medical abortion may not always be necessary; women's reports of last menstrual period (LMP) alone may be sufficient," Elizabeth Raymond and Hillary Bracken of Gynuity Health Projects wrote.

According to the authors, the review "cited two studies that found that if medical abortion had been provided to all women who reported LMPs beginning within the prior 63 days, a commonly used limit for outpatient treatment, only 3.3% and 7.2% of all patients seeking abortion would have received the drugs at GAs above that limit as assessed by ultrasound." The authors noted that while "[a] policy that allowed as many as 7% of patients to receive outpatient medical abortion treatment despite a true GA of [more than] 63 days may seem daunting ... recent data have indicated that medical abortion may be safe and effective through at least 70 days of gestation."

In this study, the researchers "reevaluated the available data to assess the utility of LMP alone for excluding pregnancies with durations of more than 70 days" and "sought to determine whether restricting the LMP-based cutoff to 56 days could reduce the risk of missing women ineligible for medical abortion."


Raymond and Bracken assessed the five studies and their reference lists cited in the review to identify studies that had "data on the number of patients presenting for abortion with GAs of more than 63 or 70 days by ultrasound but less than those or other specific limits by LMP." The researchers also examined the original data for one of the five studies.

Raymond and Bracken used the original and published data from the studies to calculate the share of women in each trial who, if GA eligibility has been determined solely using LMP-based criteria, might have received medical abortion at GAs greater than 63 and greater than 70 days "by ultrasound dating."


Raymond and Bracken included three studies in their final assessment, which were conducted between 1997 and 2007. Of those, two were included in the review -- labeled Bracken and McGalliard -- and another, labeled Ellertson, which "had been excluded from the [original] review."

According to the authors, the Bracken, Ellertson and McGalliard studies, respectively, found that 3.5%, 12% and 14% of women "with LMPs within the prior 63 days" had GAs greater than 63 days when examined via ultrasound. However, the Ellertson and Bracken studies also found that at least 50% of those with ultrasounds confirming GAs greater than 63 days had been pregnant for less than or equal to 70 days. Overall, "the proportion of women with GAs of [less than] 63 days by LMP who had GAs of [greater than] 70 days by ultrasound were 1.2% in the Bracken study and 7% in the Ellertson study," the authors wrote.

Further, the review found that the share of women "with LMPs within the prior 56 days and of women who were uncertain of their LMP dates, the proportion with a GA of [greater than] 70 days by ultrasound was even lower." Specifically, the Bracken study found that of the 63% of women who were certain their LMPs occurred less than 56 days prior, just 0.6% had GAs greater than 70 days as confirmed by ultrasound, while "[t]he corresponding proportion in the Ellertson study was 7.8%." Meanwhile, "[o]f women with GAs [greater than] 70 days by ultrasound, the proportion with certain LMPs [greater than] 56 days prior was similar in the two studies: 56/72 (78%) in the Bracken study and 32/39 (78%) in the Ellertson study."


The review shows "that, in selected women, confirmation that GA is no more than 63 or 70 days of gestation can be effectively obtained by history alone," the authors wrote. They added, "In particular, if medical abortion without screening ultrasound had been offered to all patients who reported a certain LMP no more than 8 weeks (56 days) prior to presentation, nearly two thirds could have avoided this test, and only 1.5% would have been exposed to risks associated with medical abortion after 63 days of gestation." Further, "[a]n even smaller proportion -- 0.6% -- had GAs of more than 70 days."

In addition, Raymond and Bracken noted that physicians could also confirm GA by other non-ultrasound methods, "such as abdominal palpation or pelvic examination." They concluded, "Given the potential benefits of omitting the screening ultrasound in decreasing the cost of abortion, enhancing comfort and efficiency, and ultimately increasing access to the service, we suggest that a concerted research effort to investigate this promising approach should be a priority."