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From 1980 to 1989, 141.893 newborns were screened for hip instability in Southeast Norway, a region with 34% of the country's population. The incidence of neonatal hip instability was 10.5 in 1,000 in both the first and second 5-year periods. Late diagnosed developmental dislocation of the hip (DDH) developed in 325 children: 2.3 in 1,000 (0.8 in 1,000 luxations and 1.5 in 1,000 subluxations). There were no significant differences in the two 5-year periods, and the incidence of late cases was about the same as in the 1960s and 1970s. Median age at diagnosis was 5 months; only 21 (6.5%) were detected after age 1 year. The proportion of females was 89.8%, and 7% had breech presentation as compared with 15.9% of the overall neonatal cases. The right side was affected in 30.8%, the left was affected in 35.4%, and both sides were affected in 33.8%. The results indicate that the hips of most infants who later develop DDH are stable at birth. Infant hips should therefore be examined at regular intervals at child welfare clinics.