Check her thyroid if you have not done so already. It will depend on how overweight she is as to whether there will be conception problems. Also keep in mind that she should physically be in good shape to whelp her litter. Good muscle tone and endurance.
I bred my overweight girl last fall and she had uterine inertia when it came time to deliver. Worse, the subsequent C-section came with assorted problems of its own. Each case is different though so if your girl is heavy but well conditioned, I'd say to go ahead. If I ever do something like that again I'm going to make sure the bitch gets lots of exercise previous to whelping.
BTW, this girl is just heavy by nature and has a slow metabolism. I had her tested to see if there were any medical issues but she was healthy as a horse. Her sister also is laid back and gains weight easily.
Unfortunately I have had experience with this as my girl was overweight and it has been difficult to catch her because of this. Her thyroid was Normal.
Now that she is much less heavy, my Vet feels that she will have better chances catching this time then the last 2 times.
Any bitch being bred should look like an athelete. You are asking her to run a marathon, it behooves us to prepare them for it. You and only you are responsible for the weight of your dog, take it seriously or don't breed her.
Weight is no longer something that is not considered a health risk , in humans or canine .
Bitch had a litter of 8 puppies. When the owner bred her a second time her weight had gone from 75 pounds to 92 pounds. This time she had 3 puppies. You would do better by getting your fat girl's weight down and breeding her on her next season.
Seriously, what you feed is not the big thing, as long as it is a decent food. What is key is the amount. Over the years I have learned that my dogs do perfectly well on less food. Our bodies adapt to what we eat, or in the case of dogs, what they are given. Dogs bodies will use food more efficiently if the amount is reduced. In order to get a dog to lose weight, you really have to significantly reduce the amount of kibble or it will make no difference. Then do not expect to get the weight off over night. Think in terms of months -2, 3, 4, or even more.
Feed less of the best food you can give her, and make sure that nobody in the family is giving her table scraps or treats! You have to watch your family like a hawk!
Pat Hastings recommends halving the normal amount and using salt-less rice cakes to make up the difference in volume, so they won't feel like they are starving. I have also heard of people using cooked green beans instead of rice cakes.
Purina Weight Management with a crap ton of swimming and exercise
Costco carries a *light* Kirkland food that I have a few of my Labs on successfully. I'm pleased with how much it has helped. They have had increased exercise and swimming. 2 of 3 have lost weight while on the food for 6 mo. Now, 1 of my girls that isn't losing at all will have her thyroid testing repeated for a 3-rd time with Jean Dodds. I can't think of anything else but a sluggish thyroid. She's still quite heavy. Levels slowly drop but she hasn't hit a true sluggish thyroid in her past tests so Dr. Dodds said absolutely do not treat her for a slugghish thyroid, she doesn't have it yet.
The breed gains easily and most of our dogs that have thyroid panels done are in the lower normal range.
What shocks me is some breeders give a thyroid supplement for low-normal which is not acceptable. The dog must be below the normal range or severe damage can occur.
I personally know of 4 dogs, over a decade that were supplemented and not below normal. 3 of them wound up with non-epileptic seizures, 1 wound up with a form of thyroid cancer after supplemented for years. All 4 had low, normal range thyroid levels.
A lighter food and increased exercise done at a slow rate can help with dog weight loss in the same way as people.
If the OP's bitch is a little overweight but toned and muscled, she should do fine. I would keep her fit and not allow her to gain too much during pregnancy. Try to get more weight off her if you breed her again later on. The OP's problem isn't uncommon with Labs.