Spontaneous post-implantation embryo resolution: A new concept in embryo loss

Objective: To determine and compare in an ART population the chances of complete abortion rate, and of spontaneous post-implantation embryo resolution (SPIER) (partial re-absorption of 1 or more gestational sacs) in clinical pregnancies according to the original number of gestational sacs observed. Design: A prospective, on going study in a University-based private practice and in a public hospital facility ART units. Materials and Methods: We studied the outcome of 620 pregnancies originated from ART. There were 414 singletons (67%), 132 twins (21%), 48 triplets (8%), 19 quadruplets (3%) and 7 quintuplets (1%). At the first ultrasound observation of the clinical pregnancies (20-30 days, post-conception) we detected 414 single gestational scans (44%), 264 double (28%), 144 triple (10%) 76 quadruple (8%) and 35 quintuple sacs (4%). Results: A) complete pregnancy loss was observed in 22% of all pregnancies (n:160) with the following distribution: Singleton (29%), twin (10%), triplet (8%), quadruplet pregnancies (10%), and quintuplets (14%) respectively. The pregnancy loss decreased proportional to the magnitude of the multiple gestation, being statistically significantly higher in the group of patients with singletons (p<0.05). B) SPIER was found to be overall of 29% (n:293), with the following distribution; 29% in singletons, 25% in twins 24% in triplets, 45% in quadruplet pregnancies, and 54% in quintuplets, respectively. The chance of losing a gestational sac does not differ between patients that originally had a singleton, twins or triplet pregnancies. However, it was statistically greater in those that began the gestation as a quadruplet. (p