I am no doctor, but my field is close enough. If that was from a MD, that must be a MD from Mongolia!!! The particular point that foreign tissue can "precipitate" in a woman's womb for such a long period (assuming to be longer than 1 week), is totally BS. First of all, we all know our body defense will kill all the foreign matter that is considered "not belonging to ourselves", unless the foreign matter bury deep inside your cells and do nothing like virus integrated into your chromosome. Secondly, the most ideal conditions will enable a sperm to survive for 6-7 days. The conclusion, the MD is a crook, the kid may be from the wife's last boyfriend (it is easily verified by a genetic test of the kid and the couple, all they need is a cotton swab inside their mouth). Here is a link for the survival time of the sperms:
http://www.early-pregnancy-tests.com/sperm.html