Failure Rate of Medical Treatment for Miscarriage Correlated with the Difference between Gestational Age According to Last Menstrual Period and Gestational Size Calculated via Ultrasound

Objective: To study whether the interval between gestational age calculated using the last menstrual period (GA-LMP) and gestational age calculated via ultrasound (GA-US) is correlated with the success rate of medical treatment in cases of miscarriages. Methods: This was a retrospective cohort study conducted in a gynecology unit in a tertiary medical center. Women who underwent medical treatment with Misoprostol for miscarriage at the Edith Wolfson Medical Center between 07/2015 and 12/2020 were included. Incomplete or septic miscarriages, multiple pregnancies, patients with irregular periods, and cases of missing data were excluded. Failure of medical treatment was defined as the need for surgical intervention due to a retained gestational sac, severe bleeding or retained products of conception. The cohort study was divided into two groups: patients with successful treatment and patients for whom surgical intervention was eventually needed. We performed both a univariate and multivariate analysis in order to identify whether a correlation between GA-LMP and GA-US interval is indeed a factor in the success rate of a medical abortion. Results: Overall, 778 patients were included in the study. From this cohort 582 (74.9%) had undergone a successful medical treatment, while 196 (25.1%) required surgical intervention due to the failure of medical treatment, as defined above. The GA-LMP to GA-US interval (in weeks) was 2.6 ± 1.4 in the success group, while the GA in the failure group was 3.1 ± 1.6 (p < 0.001). After performing a multivariant regression analysis, we were able to show that the GA-LMP to GA-US interval was found to be independently correlated with an increase in the treatment failure rate (aOR = 1.24, CI 95% (1.01–1.51), p = 0.03). Conclusions: In cases of miscarriage, longer GA-LMP to GA-US interval has been shown to be an independently correlated factor to lower success rate of the medical treatment option.