Here an attempt to analyze the scientific aspects of the Theory of Karma
1. You cannot dissociate the past from the present, and indeed, from the future, because space-time is continuous (from the Theory of Relativity).
2. You reap what you sow - If your parents did drugs you would most likely end up with a developmental disorder.
3. You are a reincarnation of your parents, and your offspring are a reincarnation of you - this is justified by genetics as you inherit genes from your parents, and your offspring from you.
This could be interpreted as a modern interpretation of the Theory of Karma, which would be acceptable to even the most die-hard skeptic.