Original Research
Obstetrics
Prediction of cesarean delivery in the term nulliparous woman: results from the prospective, multicenter Genesis study

Presented orally at the Society of Maternal Fetal Medicine, Atlanta, GA, Feb. 1−4, 2016.
https://doi.org/10.1016/j.ajog.2017.02.017Get rights and content

Background

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.

Objective

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.

Materials and Methods

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.

Results

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).

Conclusion

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.

Section snippets

Materials and Methods

This was a prospective, multicenter, blinded observational study conducted between October 2012 and June 2015. Nulliparous women were invited to participate at each of the 7 Perinatal Ireland Research Consortium sites (Rotunda Hospital, Dublin; National Maternity Hospital, Dublin; Coombe Women and Infants University Hospital, Dublin; Galway University Hospital, Galway; University Maternity Hospital, Limerick; Cork University Maternity Hospital, Cork; and Royal Jubilee Hospital, Belfast). There

Results

The study population profile is described in Figure 1. A total of 2392 study participants were recruited. There were 56 (2.3%) participants excluded for the following reasons; lost to follow-up (n = 4), abnormal biophysical profile (n = 33), EFW < 2.5 kg or > 5 kg (n = 5), EFW performed after enrollment (n = 5), and preexisting indication for CD, such as breech presentation and placental abruption (n = 9). Therefore, a total of 2336 women were included in the final analysis, and they

Principle findings

Five parameters were identified as clinically informative in the estimation of overall risk of CD in the term nulliparous woman, namely advancing maternal age, increasing maternal BMI, shorter maternal height, larger fetal HC, and larger fetal AC, the latter blinded ultrasound-derived data obtained after 39 completed weeks’ gestation. All such parameters are either available routinely or easily obtainable. These findings are consistent with previous studies on factors contributing to increasing

Conclusion

This nomogram, using 5 parameters (maternal age, BMI, height, fetal HC, and fetal AC), has the potential to assist with individualized consultation and thereby optimal selection of women for a successful vaginal delivery. It also may serve as an audit tool for improved monitoring of primary CD rates in nulliparous women at a hospital or population level. We believe that this risk tool will be useful for reassuring most women regarding their likely success at having an uncomplicated vaginal

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    The authors report no conflict of interest.

    This research was funded by the Health Research Board of Ireland.

    Cite this article as: Burke N, Burke G, Breathnach F, et al. Prediction of cesarean delivery in the term nulliparous woman: results from the prospective, multi-center Genesis study. Am J Obstet Gynecol 2017;216:598.e1-11.

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