ART results with frozen oocytes: data from the Italian ART registry (2005-2013).

Purpose: This study is a retrospective collection of aggregated data from all the Italian ART centers reporting to the Italian National Register from cycles started between January 2005 and December 2013.

Methods: Data from both slow freezing (SF) and vitrification (V) were assessed for the period 2007-2013, while during the years 2005-2006 cryopreservation was exclusively performed by SF.

Results: In the study period, a total of 2,526,024 oocytes were retrieved (from 378,543 retrievals), of which 1,346,061 (53.3 %) were inseminated in fresh cycles and 214,481 (8.5 %) were cryopreserved. Cryopreserved oocytes were used in 24,173 cycles yielding 19,453 transfer cycles (80.5 % of the thawing/warming cycles) and 3043 clinical pregnancies (15.6 % per transfer). A significant difference in implantation (8.7 vs 12.9 % OR 1.30 CI 1.20-1.40) and pregnancy rates per transfer (12.2 vs 14.9 % OR 1.34 CI 1.23-1.46) was found between SF and V. Complete outcome data was available for 2708 pregnancies (89.8 %), leading to 1882 deliveries and 2152 live births. Neonatal major congenital anomalies were 0.9 % (20/2152).

Conclusions: A wide variation in pregnancy rates were found among different centers and lower rates were reported in donor cycles and in centers with more experience.