Quoting Tara Annie:" Ok just to set up why I asked that question is because my son WAS sick. His skull never closed from his ... [snip!] ... and baby. Thank you to those that have been kind about this I was just curious cause sometimes I feel like I'm the only one."
personally i have not had an abortion due to this, but i can give some hope. both sperm and egg go through very complicated procesess before they reach the final stages of development, all it takes is one mistake. one little gene, and anything can happen. it is said that everyone on the planet has about three deadly diseases that they carry but are inert because they are recessive. there is a prominent rate of failure in copying genes and splicing, usually causing termination prior to the parent finding out. sometimes its not that severe, and the fetus can grow in the womb but can never survive outside, which was your case.
my dads GF had a blighted ovum, it broke her heart. she has gone on to have other children. honestly, things like this are sadly common. i would follow the other posters advice and talk to a genetic counselor.
they can look at the make up of you and your SOs DNA and tell you if you both have one of those diseases, if you both do then the odds are higher that it will happen again, but not generally 100% still because you would both have the dominant-not sick gene.
it may also have just been a fluke, like i said a lot of things can go wrong in cell reproduction, before or after conception. i would say that the fact that it wasnt something directly caused by you, like a weak cervix or whatever, then the odds are much better that it was a fluke
good luck though, i hope i helped a little....