My DH returned last year (August) from a deployment in the Middle East. It was a high stress/high heat environment. Male reproduction and heat do not go well together and we figure that lost baby #1 was conceived the weekend he got home. He also smoked a great deal during that time.
Second baby was conceived over Christmas. The hormones seemed to be really strong and I was so excited. then the moment came that I knew something was wrong. Had an early sonogram and again not viable. I went through labor and delivery in my own bedroom alone with my family downstairs. My heart was ripped out.
So the reason I think that progesterone is key is because when we were trying to have our first child I was put on hormones to conceive. Then after he was born I was on progesterone heavy birth control. Shortly after stopping that kind of BC I conceived our 2nd child unexpectedly.
I have convinced my doctor to give me progesterone with any pregnancies going forward...wish me luck!