Received November 10, 2012
Accepted December 17, 2022

Objecive:Multiple birth, due the transfer of more than one embryo, constitutes the most serious complication for both mother and children after assisted reproductive technology. Embryo cryopreservation allows the sequential transfer of the whole cohort of embryos generated in one ART cycle, either by electively transferring one embryo(eSET) or two embryos(eDET). Methods:We reviewed the database of ART procedures reported to the Latin American network of ART(REDLARA) by 140institutions in 2010. We identify eSET, eDET, and 3ET and 4ET when three and four or more embryos were transferred, respectively, and none was cryopreserved. We analysed the outcome of 808 eSET, 5,978 eDET, 4,398 3ET and 968 4ET. Results:Women that underwent eSET and 4ET were older than women that underwent eDET and 3ET(p<0.0001). The mean number of oocytes recovered was higher in women undergoing eDET (12.3) than in women undergoing eSET(6.7); 3ET(9.0); and 4ET(9.8)(p<0.0001). The clinical pregnancy rate reached 18% with eSET; 43% with eDET; 34% with 3ET;and 35% with 4ET.The proportion of twin delivery was 0.9% with eSET; when more than one embryo were transferred, the twin rate did not differ significantly: 22% with eDET; 21% with 3ET and 23% with 4ET. However, high order multiple births(≥3newborns) increased significantly with both 3ET(3.0%) and 4ET(4.4%). that neither the weight nor gestational age at delivery of singletons were associated to the number of embryos transferred. Conclusion:With the proper counselling regarding cumulative pregnancy rate and risks associated with twin pregnancy, and a fixed payment for all ET performed, we expect more couples-and physicians-would undergo