The prognostic value and significance of preclinical abortions in in vitro fertilization-embryo transfer programs

Preclinical abortions occur in natural conceptions as well as in in vitro fertilization-embryo transfer (IVF-ET) cycles. Nevertheless, although known, this entity is ill defined. The purpose of this study was to propose a classification of these pregnancies on the basis of pathophysiological evidence and to evaluate their future clinical impact. Of 970 IVF-ET cycles, 114cycles (11.7%) terminated in preclinical abortions. Abortions were divided according to peak beta human chorionic gonadotropin (β-hCG) values into chemical abortions (52%) occurring 2weeks after ET with β-hCG values not higher than 21 mIU/mL and peri-implantation abortions (47%) terminating spontaneously 4weeks after ET; the latter had higher β-hCG values for a longer period of time but without any sonographic evidence of gestational sac. No woman in the two groups needed curettage. After a chemical abortion, the pregnancy outcome had better ongoing pregnancy rates (24.7%) in comparison with the 17% achieved in the total IVF-ET cycles. It is concluded that these two groups most probably have different pathophysiological backgrounds and concomitantly different future clinical impacts.