There are so many factors that cause infertility to both men and women. They are the following:
Having to have STD
Alcohol
Poor diet
Stress
Being so overweight and underweight

Infertility problems is also caused by genetic factors and environmental factors as well.

There are so many factors that can make an individual infertility. There are genetics and there are also acquired. Let us pray to God that He would bless us to become His pro creators.

There are so many factors that can caused infertility. Some are hereditary, environmental factors and many other to consider. But a person can avoid infertility to happened by doing what's good and best for the body.

there are inborn but sometimes it is also acquired. Have a healthy lifestyle.

Sometimes it is caused by genetics, while at other times it is through disease/illness. To make sure, it is better to be guided by an expert physician.

It's possible. There are variety of factors that may affect a womens' fertility.

well, lots of contributing factors can cause infertility and one of the many factors are having to engaged in different unhealthy lifestyles.

it can be inborn, lifestyle, diet, past surgeries, past miscarriages and many more to mention. bottom line is, you need to know the main causes of it.

in some cases, it's genetic. are there any treatment for this? that i do not know but through semen analysis, doctor's are able to find treatment to increase healthy sperm, chances are 50/50.