Perinatal lamb mortality is a major challenge for sheep producers worldwide. Lamb losses from ultrasound pregnancy scanning to lamb marking were assessed in 125 mobs of ewes sourced predominantly from sheep flocks in southern New South Wales. In total, 103 086 lambs were marked from 100 165 ewes present at joining. Despite the majority of producers undertaking best-practice ewe management, including ultrasound scanning for pregnancy and preferential feeding of multiple bearing ewes, losses were similar to those reported previously (11% and 29% for singles and twins respectively). Non-Merino ewes had significantly lower losses than did Merino ewes, irrespective of ram type (13% versus 21%, P < 0.001). There was a tendency for mob size in twin-bearing ewes to influence survival, with a lower mob size (< 200) having lower losses (29% versus 33%, P = 0.07). These results are discussed in the context of existing extension advice about ewe management and perinatal lamb mortality.