According to Magneson, susceptibility to hyperemesis gravidarum can be predicted a few ways: First, if the mother has experienced HG in previous pregnancies, she will likely experience it in subsequent pregnancies. Secondly, the presence of a large placental mass is associated with HG, as is the case with twin pregnancies (which, according to Magneson, is why there is so much speculation that Duchess Kate is carrying twins). Third, a family history of HG, or the presence of other medical conditions, such as hyperthyroidism, can contribute to the presence of hyperemesis. While the disease had previously been thought of as having a psychological component (historically, women suffering from HG were considered to simply be seeking attention), MacGibbon stresses that HG is a real, physical condition, rather than an emotional one. That being said, the condition is so physically taxing that it can certainly take a psychological toll on the mother, so much so that she may consider termination. "In my research, I've found that one-third to one-fourth of HG pregnancies don't make it to term, either due to miscarriage or self-induced termination by the mother. The condition is much more alarming than many people realise."