Totally agree with DH on this.
Have you had all the relevant health tests done on your Lab girl and has the stud dog had his?
What are you trying to improve on with this mating?
If you are having trouble with the mating are you prepared for the pregnancy and birth? Have you got homes lined up for the pups to be?
Breeding 2 dogs is not about throwing them together to play and hope they mate - this could injure both male and female!