Would an underweight dog be at more risk during surgery?

My two dogs and cat are being spayed today. One dog and the cat, I'm not worried about, but I've been losing sleep over the other one all week. She was the runt of the litter. She's always been skinny. She eats just the same as the other but she just doesn't put the weight on, and the vets can find nothing wrong with her.They will be 1 on Feb 22nd.She's also always been a lazy, dopey dog. She's literally a furry baby she can be so pathetic at times. Of course I'll ask at the vet if she'll be ok, and won't put her in if they say she'll be more at risk of dying during the op, but I'd also like some views before I take them.

Do discuss this with the vets. They may wish to do pre-bloods on this little one before surgery.All the best and I do so hope all goes well.

You must consult with vet and all will be ok after surgery.

Much of what Mally posts here has been thought to be true for a long time, however many new ideas are coming out about spay and neuter and most of what Mally says only applies to very early spay and neuter and not to the surgery after the age of 6 months or in females after the first heat.Here is an article by Dr. Chris Zink, the sports veterinarian;http://www.caninesports.com/SpayNeuter.html