<Tr> <Td> </Td> <Td> This article relies largely or entirely on a single source . Relevant discussion may be found on the talk page . Please help improve this article by introducing citations to additional sources . (September 2008) </Td> </Tr> <P> In humans, implantation is the stage of pregnancy at which the already fertilized egg adheres to the wall of the uterus . At this stage of prenatal development, the conceptus is a blastocyst . It is by this adhesion that the fetus receives oxygen and nutrients from the mother to be able to grow . </P> <P> In humans, implantation of a fertilized ovum is most likely to occur about 9 days after ovulation, ranging between 6 and 12 days . </P> <P> The reception - ready phase of the endometrium of the uterus is usually termed the "implantation window" and lasts about 4 days . The implantation window follows around 6 days after the peak in luteinizing hormone levels . With some disparity between sources, it has been stated to occur from 7 days after ovulation until 9 days after ovulation, or days 6 - 10 postovulation . On average, it occurs during the 20th to the 23rd day after the last menstrual period . </P>

When does an embryo attach to the uterus