I was referred to a consultant when I was pregnant with DD (now 3) because of my raised BMI. My midwife did say she had to because the guidelines gave a cut off point (can't remember what it is now). I had previously been under the same consultant for fertility issues, so I suspect that might have had something to do with it.
My lovely consultant wasn't worried, saw me a 16 weeks and then again at 36 weeks and left me to the midwife for the rest of the time. No GTT test, no additional blood tests, no additional scans, in fact I had the easiest pregnancy in the world.
The staff on Labour Ward were great and let me get on with it and no mention was made of my weight. I ended up have a section and further surgery, but my consultant said that my insides are an odd shape.
I did, however, have problems with the sonographers. To a person, they all blamed the lack of clear pictures on my raised BMI, despite the fact that they couldn't get a clear picture with an internal scan in early pregnancy. My uterus tilts backwards towards my left hip which makes it difficult. It made me feel awful to see "lack of clear measurements due to increased BMI" all over my notes. I compared photos with other pregnant friends and their pictures were no clearer and in fact had spent far longer being scanned than I had. It felt like the sonographers couldn't be bothered and used BMI as an excuse.
I'm pregnant with No 2 now and no mention has been made of my weight, although the same excuses were rolled out at my 12 week scan. I have been referred to my consultant again, but only to book a section after last time.