Relaxin hormone is produced from

$A$ : If fertilization occurs, the corpus luteum is rescued from regression by human chorionic gonadotropin, which is produced by placenta.
$R$ : In first trimester the corpus luteum stimulates by $hCG$ is responsible for the production of progesterone.

The extra structure that provides nutrition to the embryo is

During the course of development, cells in various regions of embryo become variable in morphology and eventually perform diverse functions. This process is known as

All of the following statements concerning pregnancy are accurate $EXCEPT$