For a good explanation of how important a dog's hormones are to its physical and mental health, click on the link below:
Jeb - Isabell's Brother
As a responsible dog owner, if you plan to keep your dog under control at all times to avoid an unwanted pregnancy, then allowing your dog to remain intact is the healthiest option for them.
An ovary sparing spay or vasectomy would be the second best option from a health standpoint because they allow your puppy to retain their sex hormones which are necessary for many biological functions.
If you plan to do a traditional spay or neuter then it is imperative that your puppy be allowed to reach its full adult size (usually at 18 months in Doodles) in order to avoid structural issues caused from growth plates not closing properly due to pediatric spay or neuter.
Below is a link to information the pros and cons of traditional spay and neuter and on hormone sparing sterilization alternatives.
Here is a list of the Veterinarians in Maryland who offer OSS and Vasectomies:
Dr. Linda Reinhardt, West Friendship Animal Hospital (410) 489-9410
Dr. Trevor W. Ashley, Lake Shore Pet Hospital (410) 317-2028