I'm surprised I actually can't find this answer anywhere on the web.

So we have a Chi that bred for 4 days. They never tied - Only slip mated. She is currently 59 days and we did an xray yesterday. There is 1 "normal size" pup and 1 "underdeveloped" pup. The second pup is definitely tiny compared to the normal size pup, but you can see the skull, spine, rib cage, and legs. There is also quite a bit of movement where the little one is. The vet doesnt think it will be viable but we are definitely not counting the little one out yet.

My question is this. Is it possible for 2 eggs to fertilize on different days? So say 1 egg fertilized on the first day and the other egg fertilized on the fourth day which would make our little one behind 4 days on development? Regardless it is certainly tiny.

Thank you in advance for taking the time to read.

>Is it possible for 2 eggs to fertilize on different days?

Absolutely. the eggs are released over a couple of days, and fertilisation depends when viable sperm reaches them. Bitches which are mated over several days (sometimes with different sires) are likely to have the eggs fertilised over a period of a few days. However as they don't implant for about 20 days the difference in development will be negligible by the time of whelping, and any lack of development is likely due to other influences, such as a less efficient placenta.

Thank you very much for the response. No matter the result we are going to fight tooth and nail for the little one to make it. We went to a reproductive specialist vet and he wants her to try to birth naturally. Thank God, because I know most vets wouldnt give the little one a chance and would just let it go.