The standard approach to in vitro fertilisation is ovarian hyperstimulation to provide multiple oocytes, which ultimately provides greater choice of embryos, but multiple pregnancy and the complication of ovarian hyperstimulation syndrome (OHSS) have been consequences. Single embryo transfer (SET) has been successfully used voluntarily in Scandinavia and regulatory restriction is becoming more effective in many countries. Having a smaller number of oocytes following milder stimulation seems to be associated with a higher proportion of chromosomally normal embryos. Cryopreservation, particularly by vitrification, allows later replacement of thawed embryos from an earlier stimulation cycle, longer term storage for later family completion or even donation to e.g. stem cell research. Anti-Müllerian Hormone can be used to predict likely ovarian response and use of GnRH antagonists has led to claims of being able to eliminate OHSS, although its replacement of the former GnRH agonist downregulation prior to the FSH stimulation regime is only proceeding slowly. There has also been emphasis on improved embryo culture conditions, longer term culture to blastocyst stage with its resultant selection and most recently the use of time-lapse imaging within the incubator to select those embryos adhering most precisely to optimal cleavage times and their greater implantation potential. The impact of the stimulation regime on the patient has been great and has led to substantial dropout, even in countries where full funding is provided by the state. Lesser/mild stimulation has been termed patient-friendly, but the cost remains high. In the UK, although the number of IVF cycles has recently increased, the target of three state funded cycles per patient, specified by NICE, has not been reached. In most low resource economies infertility has major social consequences, yet there is minimal provision of assisted reproductive technologies to address infertility rates of up to 30% of those of reproductive age.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.