100 years is not a long time. My grandfather just died at age 99. The reverberating effects of the Russian empire conquering Finland in 1809 are basically never going to stop affecting my family unless we decide to move back to Scandinavia once global warming has made it less cold. :-)

It's reasonable to expect any major effect to take several generations to revert to mean. If the person who suffered the effect is alive and plays a part in raising a child, the effect will continue to reverberate.