endometrium

It is common in the US and Canada to use progesterone during early gestation for IVF pregnancies, to support the endometrium after embryo implantation.

Another extremely creepy aspect is how the placenta burrows into the endometrium.

Perhaps exercise could have a similar effect in diverting energy from higher-cancer-rate cells (skin, digestive tract linings, endometrium, etc.) to lower-cancer-rate cells (muscle cells)?

These contractions help release the endometrium (uterine lining) from the uterus, which produces the menstrual blood and tissue that exits via the cervix and vagina.

Pragmatically speaking, a human embryo that does not end up being properly embedded in the endometrium of a suitable uterus is not destined to become a human person.

> The solution, for higher primates, was to slough off the whole superficial endometrium Doesn't that suggest that's reason for higher primates?

In addition, consistent observational evidence indicates that regular consumption of coffee is associated with reduced risk of cancer of the liver and endometrium, and slightly inverse or null associations are observed for other cancer sites.

Before implanting the embryo has to convince the mother that it is viable by a trial of strength in a hostile environment, the endometrium, which has an auto-destruct button the mother's body can push to reject the embryo.

Even Wikipedia describes placentation like a siege: > The trophoblast, which is a collection of cells that invades the maternal endometrium to gain access to nutrition for the fetus, proliferates rapidly and forms a network of branching processes which cover the entire embryo and invade and destroy the maternal tissues.

With this physiologic destructive process, the maternal blood vessels of the endometrium are opened, with the result that the spaces in the trophoblastic network are filled with maternal blood; these spaces communicate freely with one another and become greatly distended and form the intervillous space from which the fetus gains nutrition.

Type 2 diabetes, an extreme state of glucose intolerance, is associated with elevated plasma levels of glucose and insulin, both before and after its diagnosis, and is associated with an increased risk of cancers of the liver, pancreas, colon, endometrium, kidney, and breast (1,2).

Animals that have menstrual cycles shed the endometrium through menstruation instead." This is discussed in the OP at some length.

The single most difficult place for them to grow was – the endometrium." Whoa...

If people really want the one-sentence version: "One difference is that animals that have estrous cycles reabsorb the endometrium if conception does not occur during that cycle.