Ive lambed 42ish lambs albeit pure bred shetlands.
Not one malpresentation, dead lamb at birth, any assistance needed, no lack of milk or mismothering. Half of them were first time mums. Half twins, half singles. Pre lambing, one case of twin lamb disease (lost lamb, saved Mum), post lambing one mild mastitis late on just before weaning, lamb just weaned early and went on to have her own lamb last year.
The only 2 lambs born I have lost was to a golden eagle and a dog or badger :-(
Shetlands have a v wide pelvis. Ideally breed them pure for lamb no 1 altho they should be fine with a smaller other breed. After that they can manage most breeds.
Much underrated as long as you have good fences :-))