After reading the reference supplied by Chris, it might be worth asking yourself the question, how would kammic forces know who would be a good parent and a bad parent, and how to direct embryos to "the parents they deserve".
Frankly, this seems a little far fetched to me... it seems to rely on some inate sense that there must be some kind of universal justice at play... and that everything must balance out in the end.... but if you look at the references Chris provided, you'll see that this is not what kamma is about.
Through corruption of the Dhamma comes corruption of the discipline, and from corruption of the discipline comes corruption of the Dhamma. This is the first future danger as yet unarisen that will arise in the future. You should recognize it and make an effort to prevent it. (AN 5.79)
Neither traceable in the Discourses nor verifiable by the Discipline, one must conclude thus: 'Certainly, this is not the Blessed One's utterance; this has been misunderstood by that bhikkhu — or by that community, or by those elders, or by that elder.' In that way, bhikkhus, you should reject it. (DN 16)