Objective: To assess the influence of gestational age, maternal age, and reproductive history on the risk for surgical intervention of early medical abortion.
Methods: A nationwide cohort study with eight weeks follow-up of all medical abortions induced at a gestational age <63 days among Danish women through the years 2005-2015. A multiple logistic regression model provided adjusted odds ratios (OR) with 95% confidence intervals (CI) for all the potential risk factors of interest. A division of the data into a training and validation set provided a test of the prediction performance of the model. Reported is the area under the receiver operating characteristic curve (AUC) with 95 % CI.
Results: 86,437 medical abortions were included, 5,320 (6.2%) were surgically intervened. The risk of surgical intervention increased with increasing gestational age (p<0.0001). The risk of surgical intervention peaked among women aged 30-35 years and declined for lower and higher ages (p<0.0001). The OR of surgical intervention among parous women compared to nulliparous was 2.0 (1.7-2.4) for women with a history of failed birth of placenta, 1.5 (1.3-1.6) for women with previous caesarean section, and 1.1 (1.0-1.2) for women with previous vaginal births with spontaneous birth of placenta. A history of early surgical abortion implied an OR of surgical intervention of 1.5 (1.4-1.7), and women with a previous late surgical abortion had an OR of 1.2 (1.1-1.3). Previous medical abortion implied an OR of surgical intervention of 0.84 (0.78-0.90). The AUC was found to be 0.63 (0.62-0.64).
Conclusion: In addition to gestational age, our study shows maternal age, previous delivery, and history of induced abortion to be risk factors for surgical intervention of early medical abortion. However, all these risk factors do not predict surgical intervention well, possibly indicating the subjective nature of the decision to surgically intervene a medical abortion.