Transfer of a selected single blastocyst optimizes the chance of a healthy term baby: a retrospective population based study in Australia 2004-2007.

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.