Abstract：
Fetal malpresentation, malposition, and asynclitism are among the most common determinants of a protracted active phase of labor, arrest of dilatation during the first stage, and arrest of descent in the second stage. The diagnosis of these conditions is traditionally based on vaginal examination, which is subjective and poorly reproducible. Intrapartum sonography has been demonstrated to yield higher accuracy than vaginal examination in characterizing fetal malposition, and some guidelines endorse its use for the verification of the occiput position before performing an instrumental delivery. It is also useful for the objective diagnosis of the malpresentation or asynclitism of the fetal head. According to our experience, the sonographic assessment of the head position in labor is simple to perform also for clinicians with basic ultrasound skills, whereas the assessment of malpresentation and asynclitism warrants a higher level of expertise. When clinically appropriate, the fetal occiput position can be easily ascertained using transabdominal sonography combining the axial and the sagittal planes. With the transducer positioned on the maternal suprapubic region, the fetal head can be visualized, and landmarks including the fetal orbits, the midline, and the occiput itself with the cerebellum and the cervical spine (depending on the type of fetal position) can be demonstrated below the probe. Sinciput, brow, and face represent the 3 \"classical\" variants of cephalic malpresentation and are characterized by a progressively increasing degree of deflexion from vertex presentation. Transabdominal sonography has been recently suggested for the objective assessment of the fetal head attitude when a cephalic malpresentation is clinically suspected. Fetal attitude can be evaluated on the sagittal plane with either a subjective or an objective approach. Two different sonographic parameters such as the occiput-spine angle and the chin-chest angle have been recently described to quantify the degree of flexion in fetuses in non-occiput-posterior or occiput-posterior position, respectively. Finally, although clinical examination still represents the mainstay of diagnosis of asynclitism, the use of intrapartum sonography has been shown to confirm the digital findings. The sonographic diagnosis of asynclitism can be achieved in expert hands using a combination of transabdominal and transperineal sonography. At suprapubic sonography on the axial plane only, 1 orbit can be visualized (squint sign) while the sagittal suture appears anteriorly (posterior asynclitism) or posteriorly (anterior asynclitism) displaced. Eventually the transperineal approach does not allow the visualization of the cerebral midline on the axial plane if the probe is perpendicular to the fourchette. In this expert review we summarize the indications, technique, and clinical role of intrapartum sonographic evaluation of fetal head position and attitude.
摘要：
胎儿畸形,错位,和异步是长期活跃的劳动阶段最常见的决定因素之一，在第一阶段逮捕扩张，在第二阶段逮捕后裔。这些疾病的诊断传统上是基于阴道检查，这是主观的，可重复性差。在描述胎儿错位时，产时超声检查比阴道检查具有更高的准确性。并且一些准则认可其在执行仪器交付之前用于验证枕骨位置。它对于客观诊断胎儿头部的畸形或异步也很有用。根据我们的经验,对于具有基本超声技能的临床医生，对分娩时头部位置的超声评估也很容易执行，而对虚假陈述和异步行为的评估需要更高水平的专业知识。在临床上适当的时候，结合轴向和矢状平面的经腹部超声检查可以很容易地确定胎儿枕骨的位置。换能器位于母体耻骨上区域，胎儿头部可以可视化，包括胎儿轨道在内的地标，中线,并且枕骨本身与小脑和颈椎（取决于胎儿位置的类型）可以在探头下方显示。Sinciput,眉毛,面部代表头部畸形的3种“经典”变体，其特征是顶点表现的偏转程度逐渐增加。最近建议在临床上怀疑头端畸形时，通过腹部超声检查可客观评估胎儿头部的态度。可以通过主观或客观的方法在矢状平面上评估胎儿的姿态。最近已经描述了两个不同的超声参数，例如枕骨-脊柱角和下巴-胸角，以量化非枕骨-后部或枕骨-后部位置的胎儿的屈曲程度，分别。最后,尽管临床检查仍然是诊断异步性的主要手段，使用产时超声检查已经证实了数字发现。使用经腹和经会阴超声检查的组合，可以在专家手中实现异步性的超声诊断。仅在轴向平面上进行耻骨上超声检查，可以看到1个眼眶（斜视征），而矢状缝线出现在前部（后斜视）或后部（前斜视）移位。最终，如果探头垂直于fourchette，则经会阴入路不允许在轴面上观察大脑中线。在这次专家审查中，我们总结了适应症，技术，产时超声评价胎头位置和姿态的临床作用。
