My CNM and her OB used this as part of the way to coerce me into a c-section for fetal macrosomia. First they talked about hte weight (9lb10oz estimated by U/S, 9lb8.5oz actual) and then the OB said that the AC:HC ratio was an even better predictor of Shoulder Dystocia (he cited a study, but I don't have it). They also claimed that they had missed GD in me, as this is most likely to occur with GD, and that there was no way to tell at 40 weeks if I had it. I have since gotten a hold of my records (my GTT was 67 way below the cut off of 140) and have found out they could have redone the GTT, so that was a lie. Some women are just genetically predisposed to having big babies (I had nine and ten pound cousins born vaginally) and so they are made to birth those babies.
To the OP: If you haven't already you should look at Kmom's website: www.plus-size-pregnancy.org
it has great info for pregnant women of all sizes, including information on GD. I am concerned that your care provider is going to try to coerce you into a c-section. You already pushed out an almost 10 pounder, no problem, your body was made to birth big babies. However, since you may be at slightly greater risk for SD, you should try to stay off your back to give birth (if you weren't planning to already). I would also be nervous about this particular care provider, find out how much experience they have with resolving shoulder dystocia. They should know how to do the Gaskin Manuever and/or the McRoberts Maneuver. If they start telling you horror stories about using the Zavenelli(sp?) Maneuver (pushing baby back up and performing an emergency c-section) I would find another care provider (preferably a homebirth midwife). That should only be done as a very last resort, as it has its own risks, and I wouldn't trust a care provider that uses it on a regular basis to resolve SD.