I wouldn't "automatically" r/o momo's but might proceed w extreme caution, if everything looked good. Would need an additional last minute US to confirm everything was still okay at beginning of labor, if it got that far. As others have said, so many things can get screwed up when they share a sac & placenta!
As long as 1st baby head down, I don't care what position the 2nd baby is in, once the 1st is out of the way, it has plenty of room to turn around. I've attended several where 2nd baby was transverse until the 1st one came out. Of course that is ideal for cord prolapse, so I would guard against and be watchful for that. If both are breech, that's okay, but if the 1st one is breech & the 2nd is cephalic, I'd feel better if they came between 36 & 38 wks. I'd let them go to 41 wks if both were cephalic. I would want them to birth in a hosp. if earlier than 36 wks, though often things are still okay as early as 35 wks.
My own dd had twins for her 1st time. 1st cephalic, 2nd transverse, then brought out by the feet. Why would twins for primip be any different than twins for a multip?
I never recommend US before 20 wks & even then, not routinely, only when I suspect a problem or there is some major discrepancy. When I suspect twins, I do suggest an US, mostly to be sure they aren't having TTTT issues. With my dd, 1st one, cephalic, was in front, so couldn't hear 2nds FHT's. I knew SOMETHING else was in there, felt like a head on the left, and a lesser bulge (butt) on the right, but wanted to r/o a tumor.
Midwifery is not regulated in my state, so as long as I don't use restricted items or procedures in my practice, it is legal.
All my twin birth stories are great! I love doing twins! Never have had any of them anyway but natural!
My fav was this Amish mom... sitting on birth stool, we start to see just about a quarter size sliver of babies rump. I am poised, but not touching. Next ctx, whole baby shoots out, through my hands, onto the floor! So, a little later, while waiting for ctx to resume, mom is sitting in bed, nursing baby A, when she gets this funny look on her face. She says, "Somebody take the baby, quick!" And with that baby B shoots out, heels 1st, onto the bed, as she plops baby A onto the bed next to her. At the one & only 21 wk US, both babies were cephalic, by 36 wks, One was breech & one transverse, so they decide to come butt & footling! the DVD, "the birth of Psalm & Zoya" is great too!