Eh? I've had four pigs out of six neutered or spayed. They're all happy and healthy. With a competent vet, the chance of problems with surgery is less than that of a pregnancy. MUCH less.
Read this thread on Guinea Lynx. It is one horror story of many, a sow who suffered and died due to pregnancy. I could probably find a hundred more like it.
http://www.guinealynx.info/forums/viewtopic.php?t=19950
In this world of overpopulation and euthanasia (it is estimated that 100,000 guinea pigs get a cold needle to the belly every year), I find your actions highly irresponsible.