What happens if a parent suffered major depressive disorder- are the risks the same for the child to suffer either bipolar or depression?

Not exactly: Predispositions toward depression and bipolar disorder would be present, but not necessarily at the same level as for the parent. Resiliency plays a strong role in the manifestation of any disorder.

Here are some number: One parent with bipolar disorder -> 35% chance child will have Two parent with ....bpd-> 75% chance one child will have With only depression in the parental lines the chances are much lower but there is research showing eventually genes for depression may have a common source and therefore chance is no zero. Again, so important to know both parternal and maternal psychiatric history. take care