The present invention refers to the use of N-acetyl-5-methoxytryptamine (melatonin) and/or an analogue thereof, for use in the medical or veterinary field in the assisted reproduction for promoting the mechanism of implantation of the embryo, and in particular for the prevention of implantation failure into the uterus, by topical administration of an effective amount in a mammalian subject female in need of such treatment, and related compositions, culture media and medical devices.