Prenatal risk factors for Caesarean section. Analyses of the ALSPAC cohort of 12,944 women in England.

BACKGROUND There has been an escalation in Caesarean section rates globally. Numerous prenatal factors have been associated with elective and emergency Caesarean section, some of which may be amenable to change. METHODS A population-based cohort of 12,944 singleton, liveborn, term pregnancies were used to investigate risk factors for Caesarean section using multivariable logistic regression modelling. Numerous prenatal factors were investigated for their associations with the following outcomes: first, with Caesarean section (both elective and emergency) compared with vaginal delivery (spontaneous and assisted); second, for their associations with elective Caesarean section compared with attempted vaginal delivery; and finally emergency Caesarean section compared with spontaneous vaginal delivery. RESULTS 11,791 women had vaginal delivery and 1153 had Caesarean section (685 emergency, 468 elective). Non-cephalic (breech) presentation (all Caesareans odds ratio (OR) 36.6, 95% confidence interval (CI) 26.8-50.0; elective Caesarean OR 86.4, 95% CI 58.5-127.8; emergency Caesarean OR 9.58, 95% CI 6.06-15.1) and previous Caesarean section (all Caesareans OR 27.8, 95% CI 20.9-37.0, elective Caesarean OR 54.4, 95% CI 38.4-77.5; emergency Caesarean OR 13.0, 95% CI 7.76-21.7) were associated in all analyses with an increased risk of Caesarean section. Extremes of neonatal birthweight were associated with an increased risk of Caesarean section (all Caesareans and emergency section) compared with vaginal delivery as was increasing neonatal head circumferences. In all analyses increasing maternal age (OR 1.07 per year, 95 % CI 1.04-1.09; OR 1.04 per year, 95 % CI 1.01-1.08; OR 1.11 per year, 95% CI 1.08-1.15) was independently associated with increased odds of Caesarean section. Increasing parity was associated with a decrease in risk for all Caesareans and emergency section (OR 0.63, 95% CI 0.53-0.75 and OR 0.46, 95% CI 0.33-0.63, respectively), as was the outcome of the last pregnancy being a live child. Increasing gestation was independently associated with a decreased risk of both all Caesareans and elective Caesarean (OR 0.86, 95% CI 0.80-0.93 and OR 0.52, 95% CI 0.46-0.58 respectively), whereas diabetes mellitus was associated with increased risk. These variables were not associated with emergency section. However, epidural use was associated with an increased risk of emergency Caesarean (OR 6.49, 95% CI 4.78-8.82) while being in a preferred labour position decreased the risk (OR 0.59, 95% CI 0.49-0.73). CONCLUSIONS A careful exploration of risk factors may allow us to identify reasons for the increasing rates of Caesarean section and the marked variation between institutions.

[1]  C. Wong,et al.  Is the management of epidural analgesia associated with an increased risk of cesarean delivery? , 2000, American journal of obstetrics and gynecology.

[2]  M. Permezel,et al.  Knowledge and attitudes about vaginal birth after Caesarean section in Australian hospitals , 2000 .

[3]  P. A. Poma.  Correlation of birth weights with cesarean rates , 1999, International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics.

[4]  D. Turnbull,et al.  Strategies to address global cesarean section rates: a review of the evidence. , 2002, Birth.

[5]  D. Roder,et al.  The Association of Maternal and Socioeconomic Characteristics in Metropolitan Adelaide with Medical, Obstetric and Labour Complications and Pregnancy Outcomes , 1992, The Australian & New Zealand journal of obstetrics & gynaecology.

[6]  M. Kelly,et al.  Lack of effect of walking on labor and delivery. , 1998, The New England journal of medicine.

[7]  M. Pembrey,et al.  ALSPAC--the Avon Longitudinal Study of Parents and Children. I. Study methodology. , 2001, Paediatric and perinatal epidemiology.

[8]  D. Teaf,et al.  The relationship of ambulation in labor to operative delivery. , 1997, Journal of nurse-midwifery.

[9]  M. Carnegie,et al.  Operative delivery during labour: trends and predictive factors. , 2002, Paediatric and perinatal epidemiology.

[10]  F. Castronova,et al.  Elective Induction Versus Spontaneous Labor: A Case-Control Analysis of Safety and Efficacy , 1998 .

[11]  H. Beck-Nielsen,et al.  Maternal and perinatal outcomes in 143 Danish women with gestational diabetes mellitus and 143 controls with a similar risk profile , 2000, Diabetic medicine : a journal of the British Diabetic Association.

[12]  S. Paranjothy,et al.  The National Sentinel Caesarean Section Audit Report , 2001 .

[13]  M. Robson.  Can we reduce the caesarean section rate? , 2001, Best practice & research. Clinical obstetrics & gynaecology.

[14]  Sander Greenland,et al.  Explaining the association of maternal age with Cesarean delivery for nulliparous and parous women. , 2003, Journal of clinical epidemiology.

[15]  J. Kiely,et al.  Some conceptual problems in multivariable analyses of perinatal mortality , 1991 .

[16]  A. Ohlsson,et al.  Effect of epidural vs parenteral opioid analgesia on the progress of labor: a meta-analysis. , 1998, JAMA.

[17]  Andrew R Willan,et al.  Planned caesarean section versus planned vaginal birth for breech presentation at term: a randomised multicentre trial , 2000, The Lancet.

[18]  M. Derde,et al.  Singleton Pregnancy After In Vitro Fertilization: Expectations and Outcome , 1995, Obstetrics and gynecology.

[19]  R. Cookson.  Royal College of Obstetricians and Gynaecologists. Induction of Labour full guidance published by the RCOG. RCOG Clinical Effectiveness Support Unit, London , 2001 .

[20]  G. Thurnau,et al.  The Preterm Prediction Study: association of cesarean delivery with increases in maternal weight and body mass index. , 1997, American journal of obstetrics and gynecology.

[21]  C. Juzi,et al.  Delivery after previous cesarean: a risk evaluation , 1999 .

[22]  R. Rogers,et al.  Epidural analgesia and active management of labor: effects on length of labor and mode of delivery. , 1999, Obstetrics and gynecology.

[23]  S. Segal,et al.  The effect of a rapid change in availability of epidural analgesia on the cesarean delivery rate: a meta-analysis. , 2000, American journal of obstetrics and gynecology.

[24]  S. Fein,et al.  Prepartum work, job characteristics, and risk of cesarean delivery. , 2002, Birth.

[25]  E. Rey,et al.  The prognosis of pregnancy in women with chronic hypertension. , 1994, American journal of obstetrics and gynecology.

[26]  R. Gratton,et al.  Obstetrical intervention rates and maternal and neonatal outcomes of women with gestational hypertension. , 2001, American journal of obstetrics and gynecology.

[27]  T. Bungum,et al.  Exercise during pregnancy and type of delivery in nulliparae. , 2000, Journal of obstetric, gynecologic, and neonatal nursing : JOGNN.

[28]  J. Pell,et al.  Caesarean section and risk of unexplained stillbirth in subsequent pregnancy , 2003, The Lancet.

[29]  M. Permezel,et al.  Vaginal birth after Caesarean section: an Australian multicentre study , 2000 .

[30]  J. Pell,et al.  Cesarean section and risk of unexplained stillbirth in subsequent pregnancy , 2004 .

[31]  A. Gezer,et al.  Perinatal and maternal outcomes of fetal macrosomia. , 2001, European journal of obstetrics, gynecology, and reproductive biology.