Alternative pregnancy formula

It has come to my attention that the current system of pregnancy creates situations where there will either be a low chance of pregnancy or a high chance of having dozens & dozens of children at once with very short gestation, with very little in-between. So I've decided to create some alternative formulas and let people choose which formula they would prefer to use in any given case, including mix & matching some of these formulas with some from the other page.

Chance of pregnancy

X = 1D100 + ((Mother FERTILITY * Father FERTILITY) / 100)

If X > 100, impregnation succeeds.

Number of children

Y = Mother FERTILITY / 10

Round Y up to the next whole number.

Flip coins until you get Y tails.

Number of children = number of heads + 1.

Duration of pregnancy

Z = 4D100 - (1D4 x Mother FERTILITY)

Duration of pregnancy is Z days, with a minimum of 1.