Purpose: The rate of vaginal birth after Cesarean (VBAC) rose significantly from early 80s, but declined rapidly since 1996. In this study, we try to determine if new information influence use of VBAC and examine the association between malpractice pressure and the adoption of new information.
Method: We expect that new information, identified as 1) a NEJM article published in 1996 reported that VBAC is accompanied with higher chances of maternal complications, and 2) a more stringent guidelines published by American College of Obstetricians and Gynecologists (ACOG) in 1999, would affect the rate of VBAC, and such responses may be larger for the physicians who face higher malpractice pressure. Using hospital discharge data from the HCUP National Inpatient Sample, we identified childbirth discharges with previous Cesarean during 1993-2004. Then a logit model was used to estimate the impact of new information, malpractice pressure, and their interaction on the likelihood of VBAC. Other covariates, such as women’s age, race, income, insurance, and hospital characteristics were included in the model as well.
Result: About 20% of the sample of 780,654 women had a VBAC. After controlling for time effect, the marginal effect of 1996 NEJM article on VBAC was 0.1% (p=0.69) and the marginal effect of 1999 ACOG guideline on VBAC was -4.9% (p<0.001). Malpractice pressure was negatively associated with the likelihood of VBAC. As for interaction effect, we found that an increase in the number of claim payment by one leads VBAC to decline by 0.06 percentage point; and a $1,000 increase in average claim payment lead VBAC to decline by 0.32 percentage point post ACOG 1999 guidelines. The results also showed individual and hospital characteristics have some effects on the likelihood of VBAC.
Conclusion: We found that the rates of VBAC were significantly lower after the release of 1999 ACOG guideline, but such situation didn’t apply to 1996 NEJM article. More importantly, our results also showed that physicians respond more to both kinds of new information when facing higher litigation risk. Our study identifies the impact of malpractice based on a change in beliefs about the effectiveness and risk associated with VBAC. Policymakers should provide incentives for physicians to pay attention to comparative effectiveness research and guidelines and malpractice pressure may be one such vehicle.
Candidate for the Lee B. Lusted Student Prize Competition