Completion of the Second Meiotic Division
The immediate result of sperm entry is to activate the oocyte to complete the second meiotic division and extrude the second polar body.
At fertilization, the diploid number of chromosomes is restored, the chromosomal sex of the new individual is determined and the ovum is activated to proceed to the first cleavage division.
The fertilization creates a single-celled zygote.
Thereafter, pregnancy occurs and the fetus proceeds to embryogenesis.
Reference
1. http://gizmodo.com/what-happens-to-sperm-once-theyre-inside-a-woman-1716992251