Fetal head circumference and subpubic angle are independent risk factors for unplanned cesarean and operative delivery

Giuseppe Rizzo; Elisa Aiello; Costanza Bosi; Francesco D'Antonio; Domenico Arduini

doi:10.1111/aogs.13162

Fetal head circumference and subpubic angle are independent risk factors for unplanned cesarean and operative delivery

Acta Obstet Gynecol Scand. 2017 Aug;96(8):1006-1011. doi: 10.1111/aogs.13162. Epub 2017 May 30.

Authors

Giuseppe Rizzo¹, Elisa Aiello¹, Costanza Bosi¹, Francesco D'Antonio^{2

3}, Domenico Arduini¹

Affiliations

¹ Department of Obstetrics and Gynecology, University of Rome Tor Vergata, Rome, Italy.
² Women's and Perinatology Research Group, Department of Clinical Medicine, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Norway.
³ Department of Obstetrics and Gynecology, University Hospital of Northern Norway, UiT The Arctic University of Norway, Tromsø, Norway.

PMID: 28449356
DOI: 10.1111/aogs.13162

Abstract

Introduction: The aim of this study was to ascertain whether combined ultrasound assessment of fetal head circumference (HC) and maternal subpubic angle (SPA) prior to the onset of labor may predict the likelihood of an unplanned operative delivery (UOD) in nulliparous women at term.

Material and methods: Prospective cohort study of singleton pregnancies in cephalic presentation. Pregnancies experiencing UOD secondary to fetal distress were excluded. HC was assessed transabdominally and SPA values were obtained from a reconstructed coronal plane on three-dimensional (3D) ultrasound performed translabially at 36-38 weeks of gestation. Maternal characteristics, HC expressed as multiple of median, and SPA were compared according to the mode of delivery. Logistic regression and receiver operating characteristics curve analyses were used to analyze the data.

Results: 597 pregnancies were included in the study. Spontaneous vaginal delivery occurred in 70.2% of the cases and UOD was required in 29.8%. There was no difference in pregnancy characteristics and birthweight between women who had a spontaneous vaginal birth compared with UOD. The HC multiple of median was larger (1.00 ± 0.02 vs. 1.03 ± 0.02, p ≤ 0.0001), whereas SPA was narrower in the UOD group (124.02 ± 13.64 vs. 102.61 ± 16.13, p ≤ 0.0001). At logistic regression, SPA (OR 0.91, 95% CI 0.89-0.93), HC multiple of median (OR 1.13, 95% CI 1.09-1.17) and maternal height (OR 0.95, 95% CI 0.92-0.99) were independently associated with UOD. When combined, the diagnostic accuracy of a predictive model integrating HC, SPA and maternal height was highly predictive of UOD with an area under the curve of 0.904 (95% CI 0.88-0.93).

Conclusions: Ultrasound assessment of fetal HC and maternal SPA after 36 weeks of gestation can identify a subset of women at higher risk of UOD during labor, for whom early planned delivery might be beneficial.

Keywords: 3D ultrasound; Dystocia; head circumference; labor; operative delivery; subpubic angle; unplanned cesarean section.

MeSH terms

Adult
Cephalometry*
Cesarean Section / statistics & numerical data*
Cohort Studies
Female
Head / diagnostic imaging*
Humans
Labor Presentation*
Pelvis / diagnostic imaging*
Predictive Value of Tests
Pregnancy
Prospective Studies
Risk Factors
Ultrasonography, Prenatal*