OBJECTIVE: To examine the contribution of singleton, cephalic, term (37 weeks or later) nulliparous cesarean rates to overall cesarean incidence in a single institution during a 35-year period.
METHODS: Cesarean rates were examined for 1974, 1984, 1994, 1999, 2005, and 2008, applying a 10-group classification system. Groups 1 (spontaneously laboring, term nulliparous women) and 2 (prelabor cesarean and induced term nulliparous women) were combined as a composite variable—the term, singleton, cephalic nulliparous woman.
RESULTS: Overall and term, singleton, cephalic nulliparous cesarean rates correlated throughout the 35-year period (r=0.93, P<.001). Between 1974 and 2008, overall cesarean rates increased from 5% to 19.1% and from 4.4% to 15.8% among term, singleton, cephalic nulliparous women. Term, singleton, cephalic nulliparous inductions increased from 19.7% to 32.7% (P<.001) and the intrapartum cesarean rate in term, singleton, cephalic nulliparous inductions rose from 4.1% to 27.3%. The cesarean rate in group 1 increased from 2.3% to 7.2%.
CONCLUSION: The increase in term, singleton, cephalic nulliparous cesarean rates correlated with the increase in overall cesarean rates throughout 35 years in an institution with standard management of labor. This relationship was due to an increase in both the incidence and rate of cesarean delivery within term, singleton, cephalic nulliparous inductions. Examination of the different term, singleton, cephalic nullipara components (spontaneous labor, induction, or prelabor cesarean) can help to identify major variations in practice between institutions.
LEVEL OF EVIDENCE: III