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Vet Minute: Different Sized Puppies in the Same Litter

November 29, 2022

Vet Minute: Different Sized Puppies in the Same Litter

Last updated: August 18, 2020

Why are some puppies in a litter born larger than others? In this Vet Minute, Revival's Director of Veterinary Services, Dr. Marty Greer, talks about different sized puppies in the same litter, why this happens and what you can do to help all puppies be born healthy and strong.

If you need help or have additional questions, call us at 800.786.4751.

Can Puppies of the Same Litter Have Different Sizes?

How can I help all puppies in a litter be born healthy and strong? Some customers call us and say they've had a litter born with some large, some small and some puppies that are stillborn, all in the same litter. Why does this happen and what can be done so all the puppies are born healthy and strong?

Why Are My Puppies All Different Sizes?

The first and most important answer to that is where the location of the puppies placenta was in the uterus. And the problem is unless you do a dog C-section you don't really know order. You may know birth order, but they may not necessarily be born in the order they were located in the uterus. So we'll see puppies that have been crowded between other puppies having smaller placentas and therefore they are smaller. Typically the largest puppies are the ends of the uterine horn. Remember the horn is Y shaped and so there's the ends by the ovaries so there's two places, one place at each ovary for them to have a larger puppy and then one closer to the cervix. As long as the cervix is closed and there's no infection and the puppy is near the cervix or near the ovary they're likely to be the biggest puppy. Often the biggest puppy is born first and then born last.

Why Is One of My Puppies So Small?

Some people's perception is that some of the puppies in the litter are premature and the other puppies in the litter are fully developed but actually that's probably not the case. We think that when a female ovulates, all the puppies are developing at the same time, they all start at the same time so they should all be still the same gestational age. I think that's a misconception that happens a lot. We can see infections happen in the uterus, either from bacteria that ascend up through the cervix and into the puppies that can infect the placenta development. We can have the female sick with a stomach disease, a virus or bacterial infection, that can certainly affect fetal development.

Another really important thing is to have great maternal nutrition so that she's on an appropriate diet for a breeding dog. We prefer that they are on a performance diet, a puppy or a pregnancy diet so that the females are getting adequate amounts of nutrition. We don't want them on an all stage diet when they're pregnant because they will need more nutrients during that time.

We also want mom to stay fit, we don't want her to just lay around the whole time she is pregnant and get sloppy and out of shape, that's not good for development.

The last thing that tends to be overlooked is to try to reduce the amount of stress and trauma during pregnancy. So we don't want her out and trucking about too much and we don't want overcrowding and we don't want too many other females in the household that may be stressing her out at the time when she's trying to have puppies, I don't think that's good for her emotionally or physically to have that happen. So I think there are a lot of reasons for this to happen the main thing is that we've eliminated that misconception that gestational ages and realize just like those trees that grow on the sides of the mountains, there's a lot of rock and just a tiny little bit of dirt and there's this little straggly tree growing there on the rock, sometimes that's how those placentas end up developing. They're crowded, they don't have much room to spread out, and those first and last puppies are usually the biggest ones with the crowding in the center causing smaller puppies mid-delivery. Unless you do a dog C-section you don't really know the location in the uterus.

Marty Greer, Doctor of Veterinary Medicine, has 35+ years' experience in veterinary medicine, with special interests in canine reproduction and pediatrics. She received her Doctor of Veterinary Medicine from Iowa State University in 1981. She's served as Revival's Director of Veterinary Services since 2019.

If you need help, call us at 800.786.4751.