Embryo transfer (ET) involves the placement of one or more embryos into the uterine cavity, usually by passing a catheter through the cervical os. ET is the final step in an assisted reproductive technology (ART) cycle, where a woman has undergone controlled ovarian stimulation, egg retrieval and in vitro fertilisation of her eggs. Despite the transfer of high quality embryos, many ETs do not result in a pregnancy. There are many factors which may affect the success of ET, including the presence of upper genital tract microbial colonisation. The administration of antibiotics prior to ET has been suggested as an intervention to reduce levels of microbial colonisation and hence improve pregnancy rates.