It runs in my family too. My Mom had it in all of 4 pregnancies and had to terminate one. Later, I learned that a cousin also suffered from this, as did her daughter. And I'd be willing to bet my grandmothers did too. When I experienced HG, we did hypnosis to see if we could find any resolution. At that time, I knew nothing of my Mother or family problem with HG. Under deep hypnosis, the words that came out of my mouth were,
"This is not my body, this is my Mother's body. This is everything she thought, felt and experienced."
After this, I interrogated my Mom about it and she decides to finally tell me she had it and it "runs in the family." I took this all as personal validation that my HG is a genetic problem and not "all in my head".
Family "secrets" are a sad thing. My Mom waited until I was pregnant at 37 and nearly dying to inform me of the likely risk. If I had known, I could have prepared properly or chosen never to pursue pregnancy in the first place. Instead, I was not set up with proper medical care in advance. And I was totally thrown off guard in all the worst ways with no clue what to do. I was forced to terminate because of this. As I approach 40, the days of pursuing babies is over for me and I am left childless with a lifetime left of traumatic memories, stemming from both the HG and the Loss. It's difficult for me not to feel anger towards my Mom and a whole lot of other unkind things which I won't mention here. All I can say is: Gee, thanks for telling me Mom......