This presumes pregnant/recent mothers inherent tiny oracular capacity is boosted by pregnancy, which if you think about it would be a pro-survival trait, and would be self-selecting genetically, as mothers with a stronger boosted oracular capacity would survive and pass this onto their children This may be where the human talent for magic arose from, especially as it is matrilineal.
The talented were also especially affected which would be consistent with my theory. Harry has previously split the timeline in Grave Peril, but the effect was not so pronounced because an Apocalypse was much more distant. Conversely in binding the Titan Harry split the timeline again leading to the Apocalpse being pushed back, again not producing the immediate oracular backwash the destruction of the Red Court created.
We are headed to the BAT but Harry’s decisions can bring it forward or push it back a bit, by creating new time-lines. Harry’s journey is to the one where he eventually wins the BAT, so sometimes two steps forward means taking one step back, such as killing the Red Court, Harry brought the Apocalypse forward, but it’s one he can ‘win’. Where he failed the Apocalpse was delayed due to the Red Court waiting to build its strength, but was where he totally lost.