While Jennifer's pregnancy came as an unexpected shock, and a surprise that made them happy, it was positive news in the sea of negativity surrounding Jason.
But this news brought forth many problems that had to be solved, somehow.
Amongst this was that the Celestia race was not allowed to ever find out about it, otherwise, they would simply kill Jennifer.
They wouldn't even try to expel the impurities of the other bloodlines within the baby once it was born. It was simply impossible for the other bloodlines not to influence the baby with a quarter of its bloodline from the Celestia race.
Because everyone understood the mindset of the Celestia race to a certain extent, this fact had to stay a secret until the very end.
In the best scenario, Jennifer would be able to give birth to the baby without the Celestia race finding out about it, at all.