DOES CESAREAN SECTION DECREASE THE INCIDENCE OF BIRTH TRAUMA? † 1422

The objective of this study is to determine if the increase in frequency of cesarean section (C/S) is associated with a decreased incidence of major birth trauma. A retrospective cohort study was performed looking at all neonatal cases of major birth trauma occurring from 1/89 to 12/94. Major birth trauma was defined as peripheral plexus or nerve injuries, fractures, and inadvertent surgical as well as traumatic lacerations. Neonates with minor birth trauma such as scalp clip injuries, cephalohematomas, bruises, and forceps marks were excluded. Charts of newborns and mothers were reviewed. Data was grouped into two mutually exclusive time periods (1/89 to 12/90 vs. 1/91 to 12/94) in which a significant difference in the C/S rate was suspected. The incidence of overall major birth trauma as well as the relative risk and 95% confidence interval (CI) of specific subtypes of birth trauma were calculated and compared between the time periods using the Chi-square test. To evaluate the role of changing delivery patterns on overall birth trauma, a stratified analysis and Mantel-Haenszel test were performed. The results showed that of 17,957 deliveries during the study period, 141 cases of birth trauma occurred. 137 of the 141 records were available for review, and 116 were classified as major trauma and are included in this analysis. The overall incidence of major birth trauma was 6.5 cases/1000 deliveries. During the two year time period(1/89 to 12/90), 18.3% of deliveries were by C/S, and the major birth trauma rate was 8.4 cases/1000 deliveries. During the following 4 year period, the C/S rate was 22.3% with the major birth trauma rate of 5.3 cases/1000 deliveries. A statistically significant difference in the birth trauma(χ²=6.12, p=.013) and C/S (χ²=40.80, p<.001) rate was observed. Controlling for the mode of delivery between the time periods lessened the association between time period and birth trauma incidence(χ²_MH=3.28, p=.07) suggesting that this change in C/S rate is responsible for part of the observed difference in birth trauma between the time periods. To further evaluate this finding, we compared the rates of major birth trauma between the time periods stratified by type of delivery. A significant decrease in the risk of major birth trauma in patients delivered by C/S in the later time period was discovered (RR=.46, 95%CI, 0.22-0.97), but there was no difference in those delivered vaginally. This decrease in C/S related birth trauma appeared to be mediated by a decrease in total lacerations between the time periods (χ²=11.76, p<.001) as there was no difference in the rates of other types of major birth trauma(fractures, palsies) in neonates of C/S or vaginally delivered patients. The conclusion of this study is that with a four percent increase in rate of C/S at our institution, a significant decrease in the occurrence of major birth trauma was noted. This finding cannot be explained by a decreased risk of trauma in patients delivering vaginally, but rather by a decreased risk of trauma at C/S in the latter time period.