Unfortunately, there are not irrefutable scientific evidences yet, but what it is known is that some food seems to be beneficial and other that apparently affect pregnancy rates in a detrimental way.
The first group contains food high in monounsaturated fats like olive oil, nuts or avocados whereas saturated fat would have a harmful effect on fertility. This second group would include COOFFE since, according a 2012 study published by Danish researchers, having 5 or more cups of coffee a day would reduce the chance of getting pregnant.
In addition, preliminary studies show that in women undergoing IVF (In Vitro Fertilization) with high protein and low carbohydrate diet the fertilization rate and the blastocyst rate are better.
In conclusion, since influence of food in fertility STILL needs to be assessed, a balanced diet high in monounsaturated fats and proteins, should be a good start point for couples who wish to become parents.