my midwife would not be happy w/ a 34 weeker. maybe 36 (w/ chances that dates could be off) but i've also known many women who have twins 35-39 weeks (naturally) and have full-size babies. relative w/ triplets at 33 weeks that were bigger than many twins born at that age. i also have known women who have full-size twins if they do go full term. 6-7 lbers. i don't think twins are necessarily smaller than a single baby if the mom is providing enough nutrition for all 3 of them.
also, if your baby goes LATE, they also sometimes lose weight. so even if you have a full-term tardy baby, they pretty much stabilize at a weight that their body chose. my mom (a NICU nurse) said she could actually recognize a post-term baby b/c they were skinny and wrinkled (overcooked) and said that 38-40 weeks was the best time to get them out big. then they might start shrinking. my midwife also told me not to worry about going late and having too big a baby, b/c they don't just keep getting bigger/fatter. since i've gone late so many times and don't have any problems as all my babies have been under 8lbs 8oz, i've accepted that there is good truth to what she says!
there's a lot of interesting information and ideas out there. i'm just rooting for keeping my little one in til prime-time (Jan 25-Feb 15th in my book). that said, chasing sledding kids up and down snowy hills might not be the best plan for that!!! based on yesterday's adventure.
34ish weeks? i've forgotten!!! 33+ at least. baby is stretched out most of the time- feet up in my ribs and head down low. i don't think it's curled up much at all, just going LONG! and this is at night in the recent snow storm! in my new nightie.