Semelparity
What if humans become semelparous?
Chapter 1
by 
91timhard
Semelparity and iteroparity are two contrasting reproductive strategies available to living organisms. A species is considered semelparous if it is characterized by a single reproductive episode before , and iteroparous if it is characterized by multiple reproductive cycles over the course of its lifetime.
Due to overpopulation becoming a threat to the survival of all humanity, so they used genetic engineering to change the reproductive strategy to semelparity. Women are fertile every day of their life since hitting puberty and the ejaculate of a healthy man results in fertilization in virtually 100% of cases. The catch is that men die after ejaculation and women after giving birth.