The blastula of prototherians is called

Which hormone is known as the pregnancy hormone?

Placenta acts like a

Progesterone is

$A$: Blastocyst undergoes gastrulation to produce the three germinal layers.
$R$: This involves cell movements (morphogenetic movement) that eventually help to attain new shape and morphology of embryo.

Hormones secreted by the placenta to maintain pregnancy are