A 28-year-old woman, G3P2, presents at 30 days since the start of her last menstrual period (LMP). She states that she has regular 28-day cycles, and that she had unprotected intercourse approximately 2 weeks earlier. Because the onset of her menstrual period was late, and because she was experiencing breast tenderness, she was concerned about being pregnant. A home pregnancy test confirmed her fears. The patient has heard about medical abortion in the news and is interested in having this procedure. Physical examination is unremarkable. Hegar's sign and Chadwick's sign are absent.
A gestational sac is not visible on transvaginal ultrasound, and the scan reveals no fluid in the cul-de-sac and no adnexal masses.
Based on the woman's history of a missed period and her home pregnancy test results, the diagnosis of pregnancy seemed likely. However, women may get inaccurate readings from home urine testing if they do not follow the instructions correctly or if they misinterpret the colorimetric result.46, 47 The patient did not have physical findings suggestive of early pregnancy, but her clinician recognized that these findings lack sensitivity. While the absence of a gestational sac on ultrasound is not unusual at 4 weeks' gestation, this finding is also consistent with ectopic pregnancy. To assist in the diagnosis, her provider ordered a quantitative hCG test, which returned at 1,875 mIU/mL.
The absence of a gestational sac on the ultrasound may indicate a very early intrauterine pregnancy or possibly an ectopic pregnancy. Because the patient did not report bleeding, complete spontaneous abortion is unlikely. The patient's hCG level was in a range (< 2,000 mIU/mL) at which an inexperienced sonographer might not detect the presence of a gestational sac.
The patient was given ectopic warnings and returned for a repeat scan 3 days later. At this time, the repeat sonogram showed a gestational sac with a mean diameter of 5 mm. Using the formula developed by Rossavik and colleagues,27 her clinician calculated a gestational age of 35 days, plus or minus 3 days. The patient met other criteria for medical abortion, and she received 200 mg mifepristone followed 1 day later by 800 µg vaginal misoprostol. The patient's hCG level on the day she took mifepristone was 4,820 mIU/mL.
Resolution of the Case
At her follow-up visit 5 days after taking the misoprostol, the patient reported that she bled heavily 4 hours after taking misoprostol. The patient believed that she passed the gestational sac, but was not certain. A pelvic examination revealed an involuted uterus. The repeat hCG level was 870 mIU/mL, 18% of the pretreatment value. Based on a study by Fiala and colleagues32 indicating that a post-treatment hCG level of 20% of the pre-treatment level has a predictive value of 0.995 for successful medical abortion with mifepristone/misoprostol, and earlier studies on methotrexate/misoprostol published by Schaff and colleagues29 and Creinin30 indicating that a drop in hCG level of over 50% within the first week after medical abortion was highly correlated with a successful outcome, her clinician concluded that the history, physical, and hCG findings were adequate confirmation that the abortion was complete.
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