Hello & welcome, I am Dr. B, a licensed veterinarian. I do apologize that your query wasn't addressed before. Different experts come online at various times; I just came online, read about your situation, and want to help you today. I am very sorry to hear about this terrible turn of events. Due to this species producing very developed (and therefore large) young, labour difficulties are not uncommon and we do at times need to intervene and perform a c-section even in young guinea pigs. While there is sadly nothing we can do now that Truffles has passed, I do just want to note a few bits of information for you. If you have any follow-on questions, do just click the reply button and we can discuss this situation further. Now you did note that the lad was put back in with your females, but you didn't mention if he was isolated after his surgery for any length of time. The reason I mention this is because even after castration, the male will still have a bit of semen in the tied off tubules. And because of this, we do have to keep the neutered male away from entire females for 4 weeks after neutering to ensure he doesn't have any viable semen left to impregnate the lasses. So, if he went right back in, then all the females would be at risk of pregnancy over those 4 weeks post-surgery. Furthermore, just in case you are ever in this type of position again, I do want to touch on the timeframes we have to consider when monitoring labour and delivery for this species. Once the labor begins, if we see our sow continuously straining without delivering for >10-20 minutes (or off & on for >2 hours), then we consider this a dystocia and have to intervene. The reason we only give that small period of time before intervening is because once delivery has started guinea pigs tend to deliver their young very quickly (the whole delivery can take as little as 30 minutes total with <10 minute breaks between each pup). So, any delay in delivery is a worry here and often needs to be assessed and potentially assisted. Again I am very sorry to hear about Truffles situation. Please take care & do let me know if you have any other questions I can answer for you. Dr. B.