title: Prediction of cesarean delivery in the term nulliparous woman: results from the prospective, multicenter Genesis study.
abstract: In contemporary practice many nulliparous women require intervention during childbirth such as operative vaginal delivery or cesarean delivery (CD). Despite the knowledge that the increasing rate of CD is associated with increasing maternal age, obesity and larger infant birthweight, we lack a reliable method to predict the requirement for such potentially hazardous obstetric procedures during labor and delivery. This issue is important, as there are greater rates of morbidity and mortality associated with unplanned CD performed in labor compared with scheduled CDs. A prediction algorithm to identify women at risk of an unplanned CD could help reduced labor associated morbidity.
  
  
  
  In this primary analysis of the Genesis study, our objective was to prospectively assess the use of prenatally determined, maternal and fetal, anthropomorphic, clinical, and ultrasound features to develop a predictive tool for unplanned CD in the term nulliparous woman, before the onset of labor.
  
  
  
  The Genesis study recruited 2336 nulliparous women with a vertex presentation between 39+0 and 40+6 weeks' gestation in a prospective multicenter national study to examine predictors of CD. At recruitment, a detailed clinical evaluation and ultrasound assessment were performed. To reduce bias from knowledge of these data potentially influencing mode of delivery, women, midwives, and obstetricians were blinded to the ultrasound data. All hypothetical prenatal risk factors for unplanned CD were assessed as a composite. Multiple logistic regression analysis and mathematical modeling was used to develop a risk evaluation tool for CD in nulliparous women. Continuous predictors were standardized using z scores.
  
  
  
  From a total enrolled cohort of 2336 nulliparous participants, 491 (21%) had an unplanned CD. Five parameters were determined to be the best combined predictors of CD. These were advancing maternal age (odds ratio [OR], 1.21; 95% confidence interval [CI], 1.09 to 1.34), shorter maternal height (OR, 1.72; 95% CI, 1.52 to 1.93), increasing body mass index (OR, 1.29; 95% CI, 1.17 to 1.43), larger fetal abdominal circumference (OR, 1.23; 95% CI, 1.1 to 1.38), and larger fetal head circumference (OR, 1.27; 95% CI, 1.14 to 1.42). A nomogram was developed to provide an individualized risk assessment to predict CD in clinical practice, with excellent calibration and discriminative ability (Kolmogorov-Smirnov, D statistic, 0.29; 95% CI, 0.28 to 0.30) with a misclassification rate of 0.21 (95% CI, 0.19 to 0.25).
  
  
  
  Five parameters (maternal age, body mass index, height, fetal abdominal circumference, and fetal head circumference) can, in combination, be used to better determine the overall risk of CD in nulliparous women at term. A risk score can be used to inform women of their individualized probability of CD. This risk tool may be useful for reassuring most women regarding their likely success at achieving an uncomplicated vaginal delivery as well as selecting those patients with such a high risk for CD that they should avoid a trial of labor. Such a risk tool has the potential to greatly improve planning hospital service needs and minimizing patient risk.
authors.affiliation: Royal College of Surgeons in Ireland, Rotunda Hospital, Dublin, Ireland. Electronic address: naomiburke@rcsi.ie.
authors.forename: Naomi
authors.initials: N
authors.lastname: Burke
authors.affiliation: Department of Obstetrics and Gynecology, Graduate Entry Medical School, University of Limerick, Limerick, Ireland.
authors.forename: Gerard
authors.initials: G
authors.lastname: Burke
authors.affiliation: Royal College of Surgeons in Ireland, Rotunda Hospital, Dublin, Ireland.
authors.forename: Fionnuala
authors.initials: F
authors.lastname: Breathnach
authors.affiliation: UCD School of Medicine and Medical Science, National Maternity Hospital, Dublin, Ireland.
authors.forename: Fionnuala
authors.initials: F
authors.lastname: McAuliffe
authors.affiliation: National University of Ireland, Galway, Ireland.
authors.forename: John J
authors.initials: JJ
authors.lastname: Morrison
authors.affiliation: UCD Center for Human Reproduction Coombe Women and Infants University Hospital, Dublin, Ireland.
authors.forename: Michael
authors.initials: M
authors.lastname: Turner
authors.affiliation: Royal Jubilee Maternity Hospital, Belfast, Ireland.
authors.forename: Samina
authors.initials: S
authors.lastname: Dornan
authors.affiliation: University College Cork, Cork University Maternity Hospital, Cork, Ireland.
authors.forename: John R
authors.initials: JR
authors.lastname: Higgins
authors.affiliation: Department of Obstetrics and Gynecology, Graduate Entry Medical School, University of Limerick, Limerick, Ireland.
authors.forename: Amanda
authors.initials: A
authors.lastname: Cotter
authors.affiliation: Obstetrics & Gynecology, St. Michael's Hospital, Toronto, University of Toronto, Toronto, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Geary
authors.affiliation: National Maternity Hospital, Dublin, Ireland.
authors.forename: Peter
authors.initials: P
authors.lastname: McParland
authors.affiliation: Coombe Women and Infants University Hospital, Dublin, Ireland.
authors.forename: Sean
authors.initials: S
authors.lastname: Daly
authors.affiliation: Royal College of Surgeons in Ireland, Rotunda Hospital, Dublin, Ireland.
authors.forename: Fiona
authors.initials: F
authors.lastname: Cody
authors.affiliation: Coombe Women and Infants University Hospital, Dublin, Ireland; Epidemiology & Public Health, Royal College of Surgeons in Ireland, Dublin, Ireland.
authors.forename: Pat
authors.initials: P
authors.lastname: Dicker
authors.affiliation: Royal College of Surgeons in Ireland, Rotunda Hospital, Dublin, Ireland.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Tully
authors.affiliation: Royal College of Surgeons in Ireland, Rotunda Hospital, Dublin, Ireland.
authors.forename: Fergal D
authors.initials: FD
authors.lastname: Malone
mesh_terms: D000005:Abdomen / Q000196:embryology; D001827:Body Height; D015992:Body Mass Index; D002585:Cesarean Section / Q000009:adverse effects / Q000706:statistics & numerical data*; D036861:Delivery, Obstetric / Q000706:statistics & numerical data; D005260:Female; D020567:Fetal Weight; D005333:Fetus / Q000033:anatomy & histology; D005865:Gestational Age; D006257:Head / Q000196:embryology; D006801:Humans; D007494:Ireland; D007746:Labor Presentation; D007743:Labor, Obstetric; D008423:Maternal Age; D049451:Nomograms; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D011446:Prospective Studies; D018570:Risk Assessment; D047929:Term Birth; D016216:Ultrasonography, Prenatal
keywords: Genesis study; cesarean delivery; nulliparous women; prediction algorithm; predictive tool