BACKGROUND: Established in 1967, the Medical Birth Registry of Norway has detailed accounts of all births in Norway. We have, however, only limited knowledge of obstetric practices in Norway in the decades before the Birth Registry was established. One important source is the annual reports of the Maternity Clinic in Oslo. MATERIAL: We analysed the annual reports for the period 1915-1961 with special emphasis on operative deliveries. RESULTS: The obstetric forceps was used in 6.5-12.5% (median 8.7%) of cephalic presentations. In 1960, the vacuum extractor was used for the first time. The rate of caesarean sections increased from 1.5% in the late 1930s to 6.3% in 1961. The proportion of operative deliveries increased up until 1944-55 when it was 14-16%, then fell in the years to 1960 when it was about 12%. Between 1915-1934, maternal mortality was as high as 6.4 per thousand. From the mid-1930s, it steadily decreased to 0.6 per thousand in the last five-year period. Well over one third of the deaths were caused by eclampsia or serious preeclampsia. INTERPRETATION: Birth traumas and neonatal death was the price paid for saving the mothers' lives and health. The operative activity was higher than what might be expected on the basis of the late-1960s data in the Birth Registry. The increase in caesarean sections was steepest during the Second World War, at a time when the number of deliveries in the clinic rose substantially.