Purpose of review: Embryo implantation remains the rate-limiting step in assisted conception programmes. Factors affecting the interactions between blastocyst and endometrium are subjects of current research and, sadly, have also been the subjects of much confusion. This review aims to present current thinking on factors affecting embryo development, endometrial receptivity during and around the implantation window and the evidence for and against various proposed treatment options
Recent findings: Age-related aneuploidies of the sex chromosomes and several other autosomes are now thought to adversely affect oocyte and embryo quality, leading to repeat in-vitro fertilization failures. Several small controlled trials have suggested improvements in clinical outcomes following preimplantation screening and blastocyst transfer for aneuploidy in older women. These are, however, very costly, wasteful of embryos and do not appear beneficial after the age of 40 years. Factors influencing endometrial receptivity remain largely unresolved. New technology using microarrays for gene expression profiling and progesterone receptor polymorphism may shed more light in the near future.
Summary: Giant strides have been made in studying the causative factors of implantation failure, but these have not been matched by therapeutic solutions. Many proposed interventions are of unproven value, yet can have harmful side-effects.