Remember that taking care of one newborn kitten, let alone an entire litter be could be stressful and overwhelming, if mother cat is not handling things well. (best-cat-art.com)
The Victorian research suggests that the spike is a consequence of litters of unwanted kittens, or mother cats with their kittens, rather than already owned cats being abandoned. (blackhobyah.net)
In foster, there's socialization for young kittens, space for mother cats to raise their young, and time for sick or injured cats to heal. (catadoptionteam.org)