ARE WE UNDERESTIMATING RATES OF VAGINAL BIRTH AFTER PREVIOUS CESAREANBIRTH - THE VALIDITY OF DELIVERY METHODS FROM BIRTH CERTIFICATES

Previous studies of birth certificates have not fully evaluated how ac curately they identify delivery methods that have a historical compone nt, such as repeat cesarean and vaginal birth after previous cesarean (VBAC). The authors used linked Georgia birth certificates for first a nd second deliveries to examine the accuracy of four reported delivery methods in the second pregnancy: vaginal (without previous cesarean), VBAC, primary cesarean, and repeat cesarean, as well as an indicator of a previous cesarean. From the immediate birth certificates, the del ivery method for each of the two births was classified as vaginal (V) or cesarean section (CS), which produced possible sequences of V-V, CS -V, V-CS, and CS-CS. The delivery method for the second births to 106, 049 women from 1989 through 1992 was reviewed, taking into account the historical information from the linked certificates regarding the fir st births. Only 42.0% of women with a CS-V sequence were correctly des ignated on the second birth certificate as a VBAC; 79.3% of women with a V-CS sequence were correctly designated as primary cesarean. From 1 980 through 1988, birth certificates contained a check box indicating a previous cesarean (but no VBAC box). During this period, only 75.5% of 25,491 women with a previous cesarean were so designated on the bir th certificate. These findings suggest that cross-sectional vital reco rds data substantially underestimate VBAC and primary cesarean rates.