Early medical abortion without prior ultrasound

To explore the potential for using last menstrual period (LMP) rather than ultrasound to establish gestational age (GA) eligibility for medical abortion.

We used the results of a recently published systematic review to identify studies with data on the number of abortion patients with GA more than 63 or 70 days by ultrasound but less than those or other specific limits by LMP. We analyzed data from these studies to estimate the proportion of women with GAs greater than 63 or 70 days by ultrasound in various subgroups of women defined by LMP.

We found three studies with relevant data. One enrolled 4257 medical abortion patients of whom 4% had GAs of >70 days by ultrasound. Of the 2681 who were certain that their LMPs began no more than 56 days prior, only 16 (0.6%) were >70 days by ultrasound. In a second much smaller study of surgical abortion patients, of whom 19% were >70 days by ultrasound, 90 women were certain that their LMPs started more than 56 days prior, and of those, 7 (7.8%) had GAs of >70 days by ultrasound. In the third study, which included surgical abortion patients with a mean GA of 61 days, at least 12% of the 138 patients with LMPs <63 days prior were >70 days by ultrasound.

The possibility that access to medical abortion can be enhanced for selected women by omitting the requirement for a screening ultrasound is promising and should be further investigated.

Gestational dating using LMP rather than ultrasound may be reasonable for selected patients before medical abortion.