recently , the cesarean delivery rate has been reported to be steadily increased in the united states [ 13 ] .
approximately , one - third of births in the united states are now via cesarean delivery .
the increase has been observed to be among women of all ages and race / ethnicities , in every state , and across all gestational ages .
many theories have been proffered to explain this trend , including a decrease in vaginal births after cesarean delivery ( vbac ) , decreased vaginal births of breech presentation , and increased prevalence of high risk pregnancies such as advanced maternal age and some subjective indications during labor such as nonreassuring fetal status and arrest of dilation [ 1 , 2 ] .
although cesarean delivery rates that are too low are associated with increased adverse events , cesarean delivery rates higher than the risk - adjusted expected rate for an institution have not been shown to improve maternal or neonatal outcomes , but they do add cost and unnecessary intervention .
therefore , the examination of cesarean delivery rate concerning perinatal outcomes is very important for obstetricians . to date , however , there have not been sufficient observations concerning the cesarean delivery rate in japanese populations . in this study
, we examined which specific factors contributed to the increase in cesarean delivery rate at our hospital over a 10-year period .
the protocol for this study was approved by the ethics committee of the japanese red cross katsushika maternity hospital .
our hospital is one of the major perinatal centers in tokyo , japan ( about 1,9002,000 deliveries per year ) . from january 2002 to december 2012 ,
data on the japanese singleton deliveries at 22-week gestation managed at the japanese red cross katsushika maternity hospital were collected .
demographic information and the characteristics of labor were extracted from patient charts to examine the potential factors associated with the increasing cesarean delivery rate . in this study ,
the factors were selected according to previous studies [ 13 , 5 , 6 ] : nulliparity , advanced maternal age ( 35 years ) , pregnancy - induced hypertension ( pih ) , preterm delivery , low birth weight ( lbw : neonatal birth weight < 2,500  g ) and macrosomia ( neonatal birth weight 4,000  g ) , history of previous cesarean deliveries , and breech presentation .
pih was defined as blood pressure 140/90  mmhg measured on two or more occasions at least six hours apart with the patient at rest . in our institute , the umbilical cord ph was measured at all deliveries . in addition , we do not perform cesarean sections for maternal request . in this study , to examine the effect of the increasing cesarean delivery rate on the obstetric outcome , the incidences of intrauterine fetal demise ( iufd ) , umbilical artery ph ( uaph ) < 7.1 , and severe perineal laceration ( perineal laceration either third- or fourth - degree laceration ) were calculated for each year .
logistic regression modeling was used to estimate cesarean delivery rate over time and for each factor .
linear regression was performed to estimate the trend over time for each factor , cesarean delivery rate for each factor , and obstetric outcomes .
statistical analyses were carried out using the statistical software sas version 8.02 ( sas institute , cary , nc , usa ) , and differences with p < 0.05 were considered significant .
from january 2002 to december 2012 , a total of 20,514 japanese singleton deliveries at 22-week gestation were managed at the japanese red cross katsushika maternity red cross hospital ; 4,086 ( 19.9% ) of those births were delivered by cesarean section . as shown in figure 1 , the cesarean delivery rate at our institution increased significantly during the study period ( 17.3% in 2002 versus 23.4% in 2012 , p < 0.01 ) .
maternal demographic and obstetric - fetal characteristics among the deliveries , which are potential factors associated with the increasing cesarean delivery rate , during the study period are presented in table 1 .
there was a significant increase in the prevalence of advanced maternal age ( 35 years ) during the study period ( 26.6% in 2002 versus 33.0% in 2012 , p < 0.01 ) .
figure 2 shows the changes in cesarean delivery rate for each factor during the study period .
as shown in figure 2 , the cesarean delivery rates with these factors were significantly higher than the average cesarean delivery rate among all deliveries . during the study period ,
the cesarean delivery rates in the cases of nulliparity , preterm delivery , lbw , previous cesarean deliveries , and breech presentation were increased significantly ( nulliparous women : 18.0% in 2002 versus 23.4% in 2012 , p < 0.01 ; preterm delivery : 39.5% in 2002 versus 57.5% in 2012 , p < 0.01 ; lbw : 35.8% in 2002 versus 57.5% in 2012 , p < 0.01 , previous cesarean deliveries : 66.7% in 2002 versus 90.0% in 2012 , p < 0.01 ; breech presentation : 76.2% in 2002 versus 94.5% in 2012 , p < 0.01 ) .
table 2 shows the changes in the incidence of iufd , low uaph , and severe perineal laceration during the study period . during the study period ,
the incidence of iufd and low uaph were significantly decreased ( iufd : 0.8% in 2002 versus 0.3% in 2012 , p = 0.03 ; low uaph : 3.3% in 2002 versus 1.6% in 2012 , p < 0.01 ) .
a negative correlation was found between the cesarean delivery rate and the incidence of low uaph for each year ( r = 0.92 , p < 0.01 ) .
the major findings of the current study are as follows : ( 1 ) the cesarean delivery rate at our institute increased between 2002 and 2012 , ( 2 ) one of possible reasons for the increasing cesarean delivery rate is an increase in the prevalence of advanced maternal age ( 35 years ) , ( 3 ) other possible reasons for the increasing cesarean delivery rate are the increase in cesarean delivery rates in the cases of nulliparity , preterm delivery , lbw , previous cesarean deliveries , and breech presentation , and ( 4 ) the incidence of low uaph seemed to be improved associated with the increased cesarean delivery rate
. this may be the first report examining the recent changes in cesarean delivery rate in japan .
we found the trends in careful correspondences for various high - risk deliveries leading to the increased cesarean delivery rate at our institute in japan .
these trends seem to be the same as those previously reported in the usa [ 13 , 5 , 6 ] and japan [ 79 ] .
for example , in a recent observation at other perinatal centers in japan , cesarean delivery rate was about 50% in primiparous women aged 40 years . in our institute
, there has been a significant increase in the primary elective cesarean delivery rate of singleton breech pregnancies due to medical counseling and maternal request between 2000 and 2005 .
this phenomenon is associated with the acog recommendation in 2001 , which recommended cesarean delivery for the term singleton breech
. an increased cesarean delivery rate in cases with precious cesarean deliveries seemed to be also an important factor contributing to the current results [ 13 , 5 ] . in our institute , intrapartum
asphyxia has been observed to be independently associated with cases of trial of labor after cesarean delivery ( tolac ) in singleton deliveries beyond 37-week gestation .
the asphyxia seemed to be associated with failed vacuum - extraction and/or forceps delivery during tolac .
therefore , our previous findings may be encouraging for the counseling of patients regarding a possible attempt at tolac . from our impressions , these trends in delivery modes of cases with previous cesarean deliveries and those with breech presentation have been expanded to all areas of japan . unfortunately , there are some limitations in this study with the lack of taking into consideration confounders such as education / social economic status / immigrant status / antenatal cares access , all variables known to affect mode of delivery [ 13 , 5 , 6 ] . in addition
, we believe that  defensive medicine  and litigation as an explicit incentive for performing cesarean section are unlikely to play a large role . in this study , the increased cesarean delivery rate seemed to contribute to the improvement of neonatal outcomes such as the decreased low uaph .
therefore , it appears that on a global level , the birth process is becoming more medicalised and it may need the increasing in cesarean delivery rate in japan . on the other hand ,
the increasing in cesarean delivery rate in the past has contributed to the reduction in adverse events ; however , the impact of the increasing in cesarean delivery rate on the maternal and/or neonatal outcomes further from now can not be predicted .
therefore , in the future , we have to pay attention be the changes in cesarean delivery rate and perinatal outcomes at our institute in japan . in conclusion
the incident of low uaph seemed to be improved associated with the increased cesarean delivery rate .
 
 objective . 
 we examined which specific factors contributed to the increase in cesarean delivery rate at our hospital over a 10-year period . 
 
 methods . from january 2002 to december 2012 , data on the japanese singleton deliveries at 22-week gestation managed at japanese red cross katsushika maternity hospital were collected . 
 potential factors associated with the increasing cesarean delivery rate were selected according to previous studies . in this study , 
 the incidences of intrauterine fetal demise , umbilical artery ph < 7.1 , and severe perineal laceration were calculated for each year . 
 results . 
 the cesarean delivery rate at our institution increased significantly during the study period ( 17.3% in 2002 versus 23.4% in 2012 , p < 0.01 ) . during the study period , 
 the cesarean delivery rates in the cases of nulliparity , preterm delivery , low birth weight ( < 2,500  g ) , previous cesarean deliveries and breech presentation were increased significantly . 
 the incidence of intrauterine fetal demise and low umbilical artery ph was significantly decreased , and a negative correlation was found between the cesarean delivery rate and the incidence of low umbilical artery ph for each year ( r = 0.92 , p < 0.01 ) . conclusion . at our institute 
 , the neonatal outcomes seemed to be improved associated with the increased cesarean delivery rate between 2002 and 2012 . 
1. Introduction
2. Patients and Methods
3. Results
4. Discussion