This is actually very common in any woman with preeclampsia or HELLP. They tend to be smaller and they tend to be under more molecular stress, most likely as a result of an immune conflict with the mother. (Our immune systems have to tolerate a foreign organ for an entire pregnancy, which is tricky and scientists aren't entirely sure how that works.)
One or two of the docs on the Medical Board have said that if women stayed pregnant longer, they would *all* get this - it's just that most of the time, we deliver before it is triggered. Sometimes the timing is off by a bit, and then we get sick.