F. Martelli

A narrow subpubic arch angle is associated with a higher risk of persistent posterior occiput position at birth

To determine whether the subpubic arch angle (SPA) measured by three‐dimensional ultrasound is associated with the fetal occiput position at delivery and the mode of delivery.

Narrow subpubic arch angle is associated with higher risk of persistent occiput posterior position at delivery

To determine whether the subpubic arch angle (SPA) measured by three‐dimensional ultrasound is associated with the fetal occiput position at delivery and the mode of delivery.

A New Method to Measure the Subpubic Arch Angle Using 3-D Ultrasound.

Objectives: The aim of this study was to assess the reproducibility of both a new contrast-enhancing technique (Oblique View eXtended Imaging, OVIX; Samsung) and the recently reported 3-D multiplanar technique (MPT) in the measurement of the subpubic angle (SPA) among a group of women at term gestation. In addition, we aimed to study the intermethod agreement between the OVIX technique and MPT. Methods: We acquired a transperineal 3-D ultrasound volume from 155 women with a singleton uncomplicated term pregnancy before the onset of labor. Each 3-D dataset was analyzed by the MPT and OVIX algorithm. The angle formed by the lower edges of the pubic rami (SPA) was measured twice by an operator and once by another operator for each technique in order to assess intra- and interobserver reproducibility. Reproducibility and intermethod agreement were studied by means of the intraclass correlation coefficient (ICC) and Bland-Altman method. Results: SPA measurements performed with OVIX showed high intraobserver [ICC 0.912, 95% confidence interval (CI) 0.882-0.935] and good interobserver (ICC 0.791, 95% CI 0.724-0.844) agreement, while those measured with MPT showed moderate intraobserver (ICC 0.573, 95% CI 0.457-0.670) and good interobserver (ICC 0.640, 95% CI 0.537-0.724) agreement. Whereas the intermethod analysis showed good agreement between the MPT and the OVIX techniques (ICC 0.614, 95% CI 0.414-0.757), the SPA measured by MPT were significantly wider than those measured by OVIX (125 ± 12 vs. 120 ± 11°, p = 0.006). Conclusions: OVIX is a reliable technique for SPA measurement. MPT overestimates the SPA in comparison with OVIX. Further studies are needed to assess its clinical utility.

Subpubic Arch Angle and Mode of Delivery in Low-Risk Nulliparous Women.

Objective: To assess whether subpubic arch angle (SPA) measurement before labor onset can predict labor outcome among low-risk pregnant women. Methods: 3D ultrasound volume was transperineally acquired from a series of nulliparous women with uncomplicated pregnancy at term before the onset of labor. SPA was measured offline using Oblique View Extended Imaging (OVIX) on each volume performed by an investigator not involved in the clinical management. Labor outcome was prospectively investigated in the whole study group. Results: Overall, 145 women were enrolled in the study. Of these, 83 underwent spontaneous vaginal delivery, whereas obstetric intervention was performed in 62 cases (Cesarean section in 40 and vacuum extraction in 22). The SPA appeared to be significantly narrower in the women submitted to obstetric intervention compared with those undergoing spontaneous vaginal delivery (116.8 ± 10.3° vs. 123.7 ± 9.6°, p < 0.01). At multivariate analysis SPA and maternal age were identified as independent predictors of the mode of delivery. On the other hand, the duration of labor did not show a significant relationship with SPA. Conclusions: In low-risk nulliparous women at term gestation, SPA measurement obtained by 3D ultrasound before the onset of labor seems to predict the likelihood of an obstetric intervention but not the duration of labor.

Demonstration of the Pericallosal Artery at 11-13 Weeks of Gestation Using 3D Ultrasound

Objective: To assess the sonographic visualization of the pericallosal arteries in normal fetuses at 11-13 weeks of gestation using 3D ultrasound. Methods: We prospectively enrolled women with a singleton pregnancy undergoing ultrasound at 11-13 weeks of gestation. A 3D volume with high-definition power Doppler was acquired starting from the sagittal view of the fetal head and stored in the spatiotemporal image correlation mode. The images of the pericallosal arteries were assigned a score of 0 (no visualization), 1 (visualization of the origin) or 2 (visualization of the whole course). A follow-up scan was performed in all cases at 20 weeks of gestation to assess the presence of the corpus callosum. Results: 70 patients were included and the pericallosal arteries were sonographically detectable in all cases. Image scores of 1 and 2 were obtained in 8 and 62 cases, respectively. The whole length of the vessel was between 3.5 and 4.5 mm. The vast majority of those with a score of 2 were beyond 12 completed weeks of gestation. All fetuses showed a normal corpus callosum at midtrimester and no abnormal brain findings after birth. Conclusions: The pericallosal arteries are sonographically visible since the first trimester in 3D ultrasound scans of fetuses found to have a normal corpus callosum at follow-up.

Effect of chorionic villus sampling on placental volume and vascularization in the first trimester of pregnancy

Abstract Objective: To evaluate the effects of chorionic villus sampling (CVS) on placental volume (PV), perfusion, and vasculature in the first trimester of pregnancy. Method: Uterine artery pulsatility index (PI), PV, vascularization index (VI), flow index (FI), and Vascularization Flow Index (VFI) were serially measured in 38 pregnant women who underwent CVS. Thirty-eight women who did not undergo invasive prenatal diagnosis were recruited as controls. Results: CVS was associated with a mild reduction of PI, a reduction of placental VI, FI, and VFI and with an increase in PV detected one week after the procedure. The outcome of pregnancy was similar between women of the two groups. Conclusion: Our findings showed that CVS is associated with mild placental vascular and morphological changes. However, these changes do not seem to be associated with adverse outcome.

OP19.06: Longitudinal changes of subpubic arch angle during pregnancy

Objectives: To assess the longitudinal changes of the subpubic arch angle (SPA) during the three trimesters of pregnancy. Methods: A group of 78 women was enrolled in the first trimester pregnancy. Each woman was assessed three times during pregnancy (I, II and III trimester), measuring SPA using a recently described highly reproducible 3D transperineal ultrasound (linear reconstruction with contrast enhancement technique). Repeated measures analysis of variance (rANOVA) was used to study SPA changes during pregnancy. Results: Among the 78 women recruited, 43 women were nulliparous while 35 were multiparous. 58/78 (74.4%) women had a vaginal delivery, while 20 (25.6%) women delivered by Caesarean section. SPA mean (±SD) was 121.2±9.1, 123.2±80.8, and 125.1±8.23 in the first, second, and 3rd trimester, respectively. SPA changes were statistically significant (F = 31.808, P < 0.0005), although was small. Post hoc tests using the Bonferroni correction revealed a significant progressive increase of SPA from 1st to 2nd, and from 2nd to 3rd trimester. Conclusions: SPA width increases progressively but slightly during pregnancy. Further studies are needed to explore the clinical value of these changes.