That is right.
In some rare cases, the mental state of the mother could be different from her “normal state”. For example, in the case of rape. In that case, a gandhabba matching that particular “state of mind” can take hold of the zygote. But there could be other cases, where the change could be good or bad.
– In cases like that, that gandhabba may be pulled out by kammic energy at a later time. That could result in a miscarriage.
Of course, these cases are complex, involving many factors.
P.S. It is important to note that the mental state of the mother at the time of gandhabba entering the womb that relevant.
– For example, in a rape situation, a mother’s mental state is likely to be “bad”.
– However, if the gandhabba enters the womb a day or two later, what is relevant is the mental state of the mother at that time.