Bene Gesserit
One of the most significant biological abilities of the Bene Gesserit is their control of their own menstrual cycles, and their ability to control (at conception) their child's sex. Jessica was ordered to bear only daughters to the Atreides, but defied her Bene Gesserit sisters (out of her love for the Duke) and had a son, Paul Atreides. The Bene Gesserit conspired against the Padishah Emperor Shaddam IV's desire to have a male heir and instructed his Bene Gesserit wife to give him only daughters, such as Princess Irulan.