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.
“I hope, Anuruddha, that you are all living in concord, with mutual appreciation, without disputing, blending like milk and water, viewing each other with kindly eyes.” (MN 31)
What is the final conviction that comes when radical attention is razor-edge sharp? That the object of the mind is mind-made (manomaya). (Ven. Ñāṇananda)
"If you have always believed that everyone should play by the same rules and be judged by the same standards, that would have gotten you labeled a radical 50 years ago, a liberal 25 years ago and a racist today." (Thomas Sowell)