I would actually mention to them that you are just hoping for a happy healthy birth and would like to hear that focus from them, too. It's insensitive to repeatedly mention what they are and unintentionally worries you needlessly.
Just for some reference- let me tell you MY stats:
Abigail 99'- Induced a week+ with Pit before her due date due to hypertension ( had surgery to remove my gall bladder at 7 1/2 mos pf pregnancy and had steroid injections to develop her lungs in case I went into labor) was born 7lbs, 7oz
Grace 00'- Had premature Rupture of membranes because the midwife was sure I would go into labor due to lots of false labor. I did not progress so ended up getting induced with Pit. She was 7lbs, 10oz
Miscarried at 13 weeks in 01'
Danny 02'- Went into labor morning after due date, labored for 45 minutes before transition, 15 min pushing he was out. 7lbs, 4 oz
Jacob 03'- Went a WEEK overdue (because we moved into a new house day after my due date in a new state) midwife induced me with Pit without my consent. Hard long labor. He was 7 lbs, 11 oz.
Eva Bella 06'- Went into labor 4 days before due date, she was 8lbs, 1 oz
Miscarried 13 weeks in 07'
Emmalia 09'- Went into labor a week before her due date, was born in a few hours- five minutes of pushing. 6lbs, 15 oz
Each pregnancy & birth is different. Your body doesnt say "Oops, you had a couple babies of this weight so time to mix things up!" It just does what nature tells everything to do. Outcomes are for MANY different reasons- and a LOT can be environmental.
Ive had 6 babies, but that doesnt mean this one will be FASTER, per say, or even easier. Depending on the position of the baby, how my body is, where I AM both physically and mentally- that all changes things. The fact I have a separated pubic bone CAN TELL US that pushing will be pretty quick, simply because there is more space for the baby to exit. But otherwise, it's really hard to say. Ive talked to moms with 10 kids who said that their 10th was one of their hardest and/or longest.
I would just mention to your midwives that you would appreciate if they wouldnt continue to go on and on about guesses and that you would like to concnetrate on a healthy baby outcome. :)