Just wanted to add that in addition, healthy sperm can live in the female reproductive tract for a few days, so she could also get pregnant by having intercourse the days leading up to ovulation (in optimal conditions, up to 5 days before the egg is released, but probably more likely 2-3 days).
Not sure about the small testicles, though. Have you tried the Men's Health forum?
http://www.medhelp.org/forums/Mens-Health/show/93