Using a modified Robson Classification to examine increases in cesarean delivery rates, California, 1996-2005

OBJECTIVES: To use a modified 8-group Robson Classification system to classify clinical and demographic characteristics associated with delivery; to assess the contributions of each class to cesarean rates; and to examine cesarean trends within the classes, overall and by age. The modified Robson system uses clinical parameters to classify deliveries into clinically relevant groups based on three obstetric concepts: category of pregnancy, parity, and gestational age. METHODS: Information from the California 1996-2005 linked birth certificate/hospital discharge records was used to ascertain mode of delivery, parity, previous cesarean, singleton or multiple, fetal presentation, and gestational and maternal age. Deliveries were assigned to classes within the 8-group framework and were stratified by mode of delivery and age. Cesarean rates were calculated per 100 deliveries. Overall and class-specific trends and the relative contribution of deliveries in each class to the overall cesarean rate were analyzed. RESULTS: In 1996-2005, there were over 5 million births in California; the cesarean rate increased 45% between 1996 and 2005 (from 20.9/100 to 30.4/100). About ¾ of all deliveries were assigned to two classes: single, cephalic, term deliveries among 1) nulliparous and 2) multiparous women without prior cesareans; 12-14% of deliveries were single, cephalic, term, repeat cesareans. However, repeat cesareans accounted for 40% of all cesareans and nulliparous single cephalic term cesareans accounted for 30%. Cesarean rates increased with increasing age. CONCLUSIONS: Ongoing efforts to reduce cesarean rates could make the greatest impact by targeting women with previous cesareans and nulliparous women with single, cephalic, term deliveries.