Where does an embryo usually attach to its mother?
The reception-ready phase of the endometrium of the uterus is usually termed the "implantation window" and lasts about 4 days. The implantation window occurs 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.
Where does an embryo usually implant and attach to its mother?
uterus
Implantation (human embryo)
In some animals, the mother will gnaw through the cord, thus separating the placenta from the offspring. The cord along with the placenta is often eaten by the mother, to provide nourishment and to dispose of tissues that would otherwise attract scavengers or predators. In chimpanzees, the mother leaves the cord in place and nurses her young with the cord and placenta attached until the cord dries out and separates naturally, within a day of birth, at which time the cord is discarded. (This was first documented by zoologists in the wild in 1974.)
Where does an embryo usually attach to its mother via an umbilical cord?
placenta
Umbilical cord
Umbilical cord
https://en.wikipedia.org/wiki/Umbilical%20cord
Implantation (human embryo)
https://en.wikipedia.org/wiki/Implantation%20%28human%20embryo%29
In humans, implantation is the stage of human reproduction at which the embryo adheres to the wall of the uterus. 
Implantation (human embryo)
The placenta connects to the baby via the umbilical cord, and on the opposite aspect to the maternal uterus in a species dependent manner. 
Placenta
In humans, implantation is the stage of human reproduction at which the embryo adheres to the wall of the uterus. An embryo then attaches to the mother in the placenta through the umbilical cord.