family in BC Canada has 18th child??

Ok I just read about this family in BC Canada that has had it's 18th child. Wow. I have to wonder did they do or use something to have this many. I have none and ok with that.
Their oldest it said was 23 years old and the next youngest 20 months. Now I guess I can kinda understand the whatever god gives us but 18? It would seem like the average is 3 or 4, and most families I know that don't try to prevent pregnancy have 5.
I thought the family with 10 that moved in was extreme, that youngest was an uncle before he was even born.
I don't see how you have that many kids without trying. I understand how to prevent, and why familes choose not to but this woman is nothing but pregnant her whole marriage. Help me to understand there doc.

goof'schik