There are several factors that can increase your odds of having twins. They include: 1. Genetics The number one factor in conceiving twins is genetics. Fraternal twins are a result of two eggs being released in the same cycle and both being fertilized. This is hyperovulation and is a result of genetics. (This is what makes twins 'run in families.' The trait of hyperovulation is passed on.) 2. Age The older you get, the more likely you are to have twins. After about 35 years of age, your hormones shift and you become more likely to hyper ovulate. (Think of it as your body going through an 'everything must go sale.' ;) ) 3. Previous Pregnancies If you have previously conceived fraternal twins, you are more likely to conceive them again. (Scroll down, there is more on this.) And overall, the more pregnancies you have had the more likely you are to conceive twins. Scientists aren't really sure why yet, but it is a trend that has been documented. (And there isn't a firm number on how many pregnancies it takes.) 4. Height Taller women are more likely to have twins. Now this doesn't mean that those of us who would definitely not be considered tall won't have twins, but it does seem to up the odds. 5. Diet There is some evidence that diet can influence having twins. (This could be simple causation correlation though, so don't go out and eat only 'twin foods' and assume you will automatically get twins!) Yams, leafy greens, and tapioca are just a few of the foods thought to help your odds of having twins. 6. Race There are trends in twinning that vary by race. If you are Hispanic or Asian you have smaller odds of conceiving twins. African-American women have the highest twin birth rate. (Source)