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Background: The practice of single embryo transfer (SET) is highly accepted by clinicians in Australia. This study investigates whether the SET of blastocysts results in optimal perinatal outcomes., Methods: This retrospective population-based study included 34 035 single or double embryo transfer cycles in women who had their first fresh autologous treatment in Australia during 2004-2007. Pregnancy, live delivery and 'healthy baby' (live born term singleton of > or = 2500 g birthweight and survived for at least 28 days without a notified/reported congenital anomaly) rates per transfer cycle were compared in four groups: selective single embryo transfer (SSET), unselective single embryo transfer (USSET), selective double embryo transfer (SDET) and unselective double embryo transfer (USDET). Live delivery and 'healthy baby' rates per transfer following SSET were further compared by number of embryos available. The analysis was stratified by woman's age and stage of embryo development., Results: The highest rates of live delivery and 'healthy baby' per transfer cycle (46.2 and 38.0%) were achieved with transfer of a single blastocyst in women aged younger than 35 years. In women aged younger than 40 years, SSET had a significantly higher rate of 'healthy baby' per transfer cycle than did SDET regardless of stage of embryo development. In woman aged younger than 35 years who had SSET, there was no significant difference in live delivery and 'healthy baby' rates per transfer cycle whether two, three, four or five embryos were available. For all of these women, SSET of a cleavage embryo had significantly lower rates of live delivery and 'healthy baby' per transfer cycle compared with SSET of a blastocyst where only two blastocysts were available., Conclusions: Consultation with the patient with respect to the advantage of extended culture and selective single blastocyst transfer will result in better success rates following assisted reproductive technology treatment in Australia.

Background: Fresh embryo transfer results in higher live birth rates, while thawed embryo transfer appears to result in healthier babies. This study aims to investigate the association between the transfer of fresh or thawed embryos at the cleavage or blastocyst stage and the perinatal outcomes., Methods: This analysis is a retrospective population-based study of 150 376 autologous embryo transfer cycles in Australia during 2002-2006. The rates of pregnancy, live delivery and 'healthy baby' delivery (a single baby born live at term, weighing >or=2500 g, surviving for at least 28 days post birth and not having congenital anomalies) were compared after transfer of fresh cleavage embryos, fresh blastocysts, thawed cleavage embryos, blastocysts from thawed cleavage embryos and thawed blastocysts., Results: The live delivery rate was significantly higher for transfer of fresh blastocysts (27.9%) than for blastocysts cultured from thawed cleavage embryos (22.0%), fresh cleavage embryos (21.7%), thawed blastocysts (16.3%) and thawed cleavage embryos (15.2%). Compared with the transfer of fresh blastocysts, the likelihood of a 'healthy baby' was significantly lower for blastocysts from thawed cleavage embryos [adjusted odds ratios (AOR) 0.73, 95% confidence intervals (CI) 0.65-0.82], fresh cleavage embryos (AOR 0.67, 95% CI 0.64-0.69), thawed blastocysts (AOR 0.57, 95% CI 0.53-0.62) and thawed cleavage embryos (AOR 0.53, 95% CI 0.51-0.56). Of thaw cycles, transfers of thawed blastocysts (AOR 0.79, 95% CI 0.70-0.89) and thawed cleavage embryos (AOR 0.71, 95% CI 0.63-0.79) had significantly lower odds of 'healthy baby' than transfer of blastocysts from thawed cleavage embryos., Conclusions: These data suggest that an optimum practice model to maximize the outcomes of the birth of a 'healthy baby' is the transfer of blastocysts and the freezing of cleavage embryos in fresh cycles and subsequent transfer of blastocysts cultured from these thawed cleavage embryos.