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Visualization of the fetal fontanels and skull sutures by three‐dimensional translabial ultrasound during the second stage of labor

2008; Wiley; Volume: 31; Issue: 4 Linguagem: Inglês

10.1002/uog.5309

1469-0705

Ilka Fuchs, B. Tutschek, Wolfgang Henrich,

Assisted Reproductive Technology and Twin Pregnancy

Ultrasound is superior to digital examination for determining the position of the fetal head during the second stage of labor1, 2. However, identification of the precise internal rotation and flexion of the fetal head remains difficult, especially in the second stage of labor, with the fetal head in the mid-pelvis. This is the first description of intrapartum imaging of the fetal skull by three-dimensional (3D) translabial ultrasound, which clearly indicated the sutures and fontanels and, thereby, the exact stage of internal rotation of the head in the second stage of labor. In a 27-year-old primigravid woman, vacuum extraction of the fetus was planned because of failure to progress. Ascertainment of the orientation of the sagittal suture and the position of the posterior fontanel by digital examination was impaired because of an extensive caput succedaneum. Ultrasound examination in the sagittal plane was performed with the woman in a semirecumbent position using a 3D transducer (RAB4-8, Voluson 730 Expert, GE Healthcare, Milwaukee, WI, USA) placed translabially, as described previously3. Two-dimensional (2D) ultrasound demonstrated the following structures: the inferior margin of the pubic bone, the fetal skull with molding of the parietal and occipital bones in the area of the posterior fontanel, and the caput succedaneum. In this plane the real-time 4D mode, with volume contrast imaging, was activated. The z-axis was positioned tangentially from the pubic symphysis to the vertex of the fetal skull (Figure 1a). 3D translabial ultrasound enabled us to visualize the leading posterior and the anterior fontanels, the sagittal and lambdoid sutures and parts of the coronary and metopic sutures, as well as the fetal skin of the caput succedaneum, the soft tissue of the birth canal and part of the pubic arch. This view demonstrated clearly and easily the degree of internal rotation of the fetal head at the mid-pelvis (Figures 1b and 2). Full 3D volumes displayed in tomographic mode (tomographic ultrasound imaging (TUI), Figure 3) showed the caput succedaneum, consisting of the hyperechogenic scalp and the hypoechogenic edematous subcutaneous tissue (Figure 3, level −1). In this mode, the frontal and parietal bones, with their sutures and fontanels, were apparent in adjacent parallel sections. After demonstrating these structures, accurate placement of the vacuum cup and successful extraction of the fetus could be performed confidently. Sagittal view of the maternal pelvis sub partu on translabial two-dimensional (2D) ultrasound (a) and three-dimensional (3D) volume contrast imaging (VCI) (b). The 2D image (a) demonstrates the symphysis (1), the caput succedaneum with hyperechogenic skin and hypoechogenic subcutaneous edema (2) and the fetal head with molding of the bones (3) at the posterior fontanel. The z-axis of the VCI mode can be seen as a dotted line from the symphysis to the vertex of the head. The 3D image (b) shows the fetal head with complete internal rotation: the leading triangular posterior fontanel (3), the quadrangular anterior fontanel (4), and the sagittal (5), metopic (6), coronary (7) and lambdoid (8) sutures, the fetal skin (2), the birth canal (9) and parts of the pubic arch (1) are visible (see also Videoclip S1 online). Enlarged three-dimensional volume contrast image of the fetal head in the maternal pelvis sub partu, in the same view as that in Figure 1b. Intrapartum translabial tomographic imaging. Level −1 is a horizontal section of the caput succedaneum with the echogenic circular border representing the scalp and the hypoechogenic center representing the subcutaneous edema. Levels 0 (*) and +1 show the parietal and frontal bones forming the anterior fontanel; the caput succedaneum is visible surrounding the fetal skull. Identification of the position of the fetal head and the exact degree of internal rotation are essential for a safe vaginal instrumental delivery. Correct placement of the vacuum cup or forceps blades is a prerequisite for successful instrumental vaginal delivery4-6. Digital examination of the position of the fetal head in the second stage of labor is unreliable7 and is inaccurate in up to 50% of occipital–posterior presentations1, 8. Especially in prolonged labor, a marked caput succedaneum can impair diagnostic precision9. Intrapartum transabdominal ultrasound permits accurate recognition of fetal head position10. Recent studies have shown that the descent of the fetal head is apparent on translabial ultrasound3, 11; this improves the exact placement of the vacuum cup prior to vacuum extraction12 and is likely to reduce complications of operative vaginal delivery. Sonographic assessment of the internal rotation and flexion of the fetal head is still a challenge. In the first stage of labor, the rotation of the fetal head can be determined on transabdominal ultrasound examination by demonstration of the fetal cerebellum or orbits. With progressive descent of the fetal head, transabdominal sonography becomes difficult due to shadowing by the maternal symphysis. To our knowledge, this is the first time that sonographic visualization of the fontanels and sutures of the fetal skull during the second stage of labor has been described. 3D intrapartum ultrasound demonstrates planes not available using 2D ultrasound, opening a new sonographic window during delivery. The following material is available from the Journal homepage: http://www.interscience.wiley.com/jpages/0960-7692/suppmat (restricted access) Videoclip S1 Videoclip of three-dimensional volume contrast imaging of the fetal head in the maternal pelvis sub partu. Note the anterior and posterior fontanels, the molding of the bones and the echogenic circle representing the caput succedaneum surrounding the fetal skull. This article contains supplementary material available via the Internet from the Journal http://www.interscience.wiley.com/jpages/0960-7692/suppmat (restricted access) Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.