Which hormone is known as the pregnancy hormone?

Thalidomide is a non-barbiturate sedative drug which was given to pregnant women. Its use was withdrawn in $1961$ because it resulted in phocomelia. This condition illustrates:

At which stage does cell division decrease?

Given below are two statements with respect to gastrulation.
$Statement-I$: Root of amniotic cavity is lined by amniogenic cells, which divides to form chorion.
$Statement-II$: Chorion is an embryonic membrane that participates in development of the embryo.
Choose the most appropriate answer from the options given below.

During pregnancy,the levels of which hormones are increased?

What is placenta? Give information about hormones produced by the placenta.