36DDD. What is the ideal bra size/ cup for a 4"11 petite woman?

The implant selection should be based on a combination of your desired size, soft tissue dynamics, breast base diameter and skin elasticity.  I recommend an in-office examination as well as a detailed discussion with a surgeon who you are comfortable with.   Finally, make sure your surgeon is a Double-Board Certified Plastic Surgeon certified by the American Board of Plastic Surgery (ABPS), a member of the American Society of Plastic Surgery (ASPS), a member of the American Society of Aesthetic Plastic Surgery (ASAPS), and a fellow of the American College of Surgeons (FACS).Best,Dr. DesaiBeverly Hills Institute for Aesthetic Plastic SurgeryHarvard Educated, Beverly Hills & Miami Beach TrainedDouble Board-Certified, Double Fellowship-Trained Beverly Hills Plastic Surgeon

The cup size measure has inherent variability.  Tissue density will always play a big role in the number of grams removed.  Going too small can sacrifice the shape of the breasts.  After breast reduction, your belly, legs, and arms will appear bigger than before the surgery.  The nipple has to have a blood supply to survive from the underlying tissue.  You can always tighten the skin later if not aesthetically pleasing, and breast mass will decrease with time.  If your PS told you that your insurance would cover breast reduction surgery as a medical condition, it should not have changed with your weight gain from your pregnancy.Kenneth Hughes, MD, ABPS Board Certified Plastic SurgeonLos Angeles, CA

Dear isarodbel,
breast reduction is best suited for women who wish to decrease the size of their breasts. While there are different techniques used to perform this surgery, I prefer the vertical incision (lollipop pattern) breast reduction technique instead of the anchor scar pattern, which reduces more noticeable scarring than usual. I also use a SAFE liposuction technique to reduce additional fat around the stubborn axilla area and bra line. This way, my patients are achieving beautiful results with minimal incisions which reduces downtime and delivers an overall better breast shape long term.If you are considering breast reduction surgery, you should consult with a board certified plastic surgeon to discuss your options and make sure your surgeon understands your goals. Only after a thorough examination you will get more information and recommendations.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

require that minimum weights be removed to qualify and you must see a local plastic surgeon to find out if you meet that (probably).  Reductions only guarantee that you will be smaller and if there is a minimum agreed to, your surgeon  must remove that amount so its remotely possible that you may have more tissue removed than you would have desired.  As for how much to remove, my patients could direct me to be conservative (remove only the minimums), do the procedure how I normally do them, or be aggressive for the smallest outcome possible.

There is no "right answer"; patient preferences play a very large role when it comes to determining final size  achieved with breast reduction surgery.
My best advice: select your plastic surgeon carefully. Make sure that he/she has significant experience achieving the types of outcomes you will be pleased with.
Before undergoing the breast reduction procedure it will be very important to communicate your size goals with your surgeon (who you should choose very carefully). With the goal of improving communication with my patients I find the use of photographs of “goal” pictures (and breasts that are too big or too small) very helpful.  For example, I have found that the use of words such as “natural” or “B or C cup” means different things to different people and therefore prove unhelpful. Also, as you know, cup size varies depending on who makes the bra; therefore, discussing desired cup size may also be inaccurate. 
Once you have communicated your goals carefully, your plastic surgeon will be able to provide you with an estimation of how much tissue will need to be removed, in order to achieve your desired outcome.
Best wishes

There is no ideal size, that is whatever you think it should be. But if you are having symptoms from oversized heavy breasts, then you will certainly love the changes brought about by the breast reduction procedure. Your surgeon will evaluate you and find out the insurance issues.