KatPreg

Katrina's Rules for Randomly Determining Pregnancy
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Note: Any time two characters capable of reproducing together have vaginal intercourse, there is a chance for pregnancy to occur. These rules simulate that chance randomly through the use of dice.


1. Determining fertility.

   - There is a one in three chance that the female is currently fertile.
   - Roll 1d100. A roll of 67 or higher indicates that the female is in the fertile week of her cycle. Continue to next step.
   - On a roll of 95-100, multiple eggs were potentially released. See note #4.


2. Base chance.

   - The base chance for fertilization is 20%, modified by the fertility of each partner. Determine this first by asking, and then consult the chart. The minimum chance is 1%, and the normal maximum is 60%. Fertility drugs can further increase this by 10% for each partner taking them.
   - If characters are of two different species that are capable of reproducing, add a cross-species modifier of -10%, unless the two species are compatible enough that this modifier would be irrelevant.

   - Roll 1d100. On any roll that falls under the target percentile, pregnancy occurs.

            1) Completely infertile, incapable of producing children: base 0% chance. Other partner's base chance no longer matters.
            2) Significantly lower than average: -20%
            3) Greatly lower than average: -15%
            4) Lower than average: -10%
            5) Slightly lower than average: -5%
            6) Average: -0% (Remains at the base 20% chance)
            7) Slightly higher than average: +5%
            8) Higher than average: +10%
            9) Greatly higher than average: +15%
           10) Significantly higher than average: +20%

(Use this chart as a base guide. Percentage can be altered on a point by point basis between 20% and -20%.)


3. Birth control, contraceptives, and fertility medication.

   - Using condoms or any "barrier" method of birth control like a diaphram results in a third roll. On a roll of 1-96, the contraceptive prevents pregnancy. On a roll of 97-100 (67-100 in a fantasy setting, or one with less advanced technology), the contraceptive fails, and pregnancy is rolled for normally, using the base percentage. If multiple forms of birth control are used, roll once for each form.
   - In a fantasy setting, an herbal remedy brewed into tea can reduce the chance by 10% for each partner, though it must be imbibed daily to be effective.
   - Conversely, there are also herbs which have been known to increase fertility. In this case, increase the chance by 10% for each partner taking them. Additionally, the chance of multiples is increased if the female is taking fertility medication. In such a case, use the rules from Note #6 (see below) regarding characters from species with greater than average chance of multiples.
   - Forms of birth control such as the pill drop the base percentile to 2%, modified by +/- 1% depending on each partner's fertility, to a minimum of 1% and a maximum of 4%. If both partners are using this form of birth control, roll a second 1d100 if the first roll is under the base number. If the second percentile also falls under the base number, pregnancy still manages to occur.
   - The "pulling out" method is only 50% effective.
   - If the "morning after" pill is taken immediately, there is a 99% chance of negating the pregnancy. Reduce this chance by 14% for every day after initial conception.

4. Miscellaneous notes

  Note: The safest method to prevent pregnancy is by doubling up on the forms of birth control used.
  Note #2: Only roll for fertility once per "encounter". Every time a significant amount of time has passed, roll again.
  Note #3: In the case of multiple intercourse sessions in a single encounter, reduce the chance by 5% each time until the minimum of 1% is reached.
  Note #4: If more than one egg was potentially released, there is a chance for multiples. Repeat step 2. For each roll that falls under the base chance, another egg is fertilized. For each egg that is fertilized beyond the second, reduce the chance by 5% for that "group" of rolls. (ex. A couple has sex 3 times in a single encounter, and multiple eggs were released. The base chance for each roll is 30%, 25%, 20%. The first rolls are 54, 39, and 19. One egg is fertilized, so then the next "round" begins. This time the rolls are 69, 23, and 38. The 23 confirms a second egg fertilized, triggering a third round, albeit with a reduced chance: 25%, 20%, 15%. This time the rolls are 5, 25, and 82. The 5 means that a third egg is fertilized, triggering round four. This time the chances are 20%, 15%, 10%. The rolls are 85, 91, 35. No further eggs are fertilized, and the rolling is over.)
  Note #5: To determine the chance for identical twins, roll 1d100. On a roll of 1-3, the fertilized egg will divide and twins will be born.
  Note #6: If a character is from a species that has a greater than average chance of multiples, use these rules to determine fertility instead: On a roll of 67-80, one egg was released, determine pregnancy chance normally. On a roll of 81-95, determine pregnancy chance normally, but if conception occurs, assume that two eggs were fertilized and that twins will be born. On a roll of 95-00, determine pregnancy chance normally, and if conception occurs, assume that two eggs were fertilized and that twins will be born. Then continue to roll as per the rule for multiples, with each successive positive check adding one fertilized egg to the result.


4. D&D rules:

- Fertility scales with con, and is modified by racial modifiers. Every two points of con = +/- 2% (ie. 8 con = -2%, 10 con = 0%, 12 con = +2%)

5. D&D racial modifiers:

- Dragon/kobold: +10%
- Orcs/Goblins: +5%
- Half-orcs/Goblins: +2%
- Human: 0%
- Dwarves: -1%
- Half-elf: -2%
- Elf: -5%
- Tieflings (Special case: roll randomly between -5 and +5, ie. 1d10)