Demigods are the offspring of a god and a mortal. As such, they share both godly ichor and human blood. This mixture emits a scent that, though unnoticeable to mortals and other demigods, is highly potent to monsters and attracts them to kill demigods.
Unlike mortal pregnancies, which naturally occur over nine months and are the product of sexual relationships between men and women, demigods are the inevitable product of any human/godly relationship. No protection, no gender inconceivability, no briefness of relationship will prevent the creation of a demigod once the relationship begins.
As previously stated, demigods are the result of godly relationships with mortals. Whether the god or goddess takes the form of the opposite gender--well within their capabilities--or has sexual relations with the same sex, a demigod will be produced. This is the result of godly energy merging with the human soul through shared attraction or love as a conduit.
Unlike mortals, whose pregnancies take nine months, demigod pregnancies can take anywhere from one to three months to be completed. This length of time extends to four months if it is the mortal who is carrying the demigod--as is the case with all female mortal participants in male/female relationships.
Despite their godly blood, demigods are mortal and are a part of the mortal world. As a result, the Fates decreed at the dawn of time that all demigods must be raised by their mortal parent or in the mortal world. This, of course, extends to allowing them to attend Camp Half-Blood but prohibits them from being raised solely by their godly parent.
Powers & Abilities
All demigods are dyslexic. This is a result of their minds being naturally attuned to Ancient Greek (and some Latin) which prevents them from properly understanding modern written languages. It also grants them an instinctive--though not fluent--grasp of Ancient Greek. With practice and exposure to the language, all demigods naturally become fluent in speaking Ancient Greek, though its use in daily life is rare.
Demigods are also ADHD. This is due to their natural battle reflexes which allow them to combat the many monsters and threats that come after them. In combat, demigods are able to pay attention to an entire battlefield without losing focus of the fight, and they are capable of fighting instinctively due to their unparalleled instincts in battle
Demigods also inherit certain traits from their godly parents. These traits are abilities and powers which hold a natural affinity toward their parent's sphere of influence and power. These powers--though predictable---vary from demigod to demigod and a child who inherits certain rare abilities might be the only one to do so.