Department of Obstetrics and Gynecology, Oslo University Hospital and Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
National Center for Fetal Medicine, Trondheim University Hospital, St. Olav's Hospital and Institute of Clinical and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
Am J Obstet Gynecol. 2020 Dec;223(6):909.e1-909.e8. doi: 10.1016/j.ajog.2020.06.042. Epub 2020 Jun 23.
To accommodate passage through the birth canal, the fetal skull is compressed and reshaped, a phenomenon known as molding. The fetal skull bones are separated by membranous sutures that facilitate compression and overlap, resulting in a reduced diameter. This increases the probability of a successful vaginal delivery. Fetal position, presentation, station, and attitude can be examined with ultrasound, but fetal head molding has not been previously studied with ultrasound.
This study aimed to describe ultrasound-assessed fetal head molding in a population of nulliparous women with slow progress in the second stage of labor and to study associations with fetal position and delivery mode.
This was a secondary analysis of a population comprising 150 nulliparous women with a single fetus in cephalic presentation, with slow progress in the active second stage with pushing. Women were eligible for the study when an operative intervention was considered by the clinician. Molding was examined in stored transperineal two-dimensional and three-dimensional acquisitions and differentiated into occipitoparietal molding along the lambdoidal sutures, frontoparietal molding along the coronal sutures, and parietoparietal molding at the sagittal suture (molding in the midline). Molding could not be classified if positions were unknown, and these cases were excluded. We measured the distance from the molding to the head midline, molding step, and overlap of skull bones and looked for associations with fetal position and delivery mode. The responsible clinicians were blinded to the ultrasound findings.
Six cases with unknown position were excluded, leaving 144 women in the study population. Fetal position was anterior in 117 cases, transverse in 12 cases, and posterior in 15 cases. Molding was observed in 79 of 144 (55%) fetuses. Molding was seen significantly more often in occiput anterior positions than in non-occiput anterior positions (69 of 117 [59%] vs 10 of 27 [37%]; P=.04). In occiput anterior positions, the molding was seen as occipitoparietal molding in 68 of 69 cases and as parietoparietal molding in 1 case with deflexed attitude. Molding was seen in 19 of 38 (50%) of occiput anterior positions ending with spontaneous delivery, 42 of 71(59%) ending with vacuum extraction, and in 7 of 8 (88%) with failed vacuum extraction (P=.13). In 4 fetuses with occiput posterior positions, parietoparietal molding was diagnosed, and successful vacuum extraction occurred in 3 cases and failed extraction in 1. Frontoparietal molding was seen in 2 transverse positions and 4 posterior positions. One delivered spontaneously; vacuum extraction failed in 3 cases and was successful in 2. Only 1 of 11 fetuses with either parietoparietal or frontoparietal molding was delivered spontaneously.
The different types of molding can be classified with ultrasound. Occipitoparietal molding was commonly seen in occiput anterior positions and not significantly associated with delivery mode. Frontoparietal and parietoparietal moldings were less frequent than reported in old studies and should be studied in larger populations with mixed ethnicities.
为适应产道通过，胎儿颅骨受压变形，这种现象称为塑形。胎儿颅骨由膜性缝线分开，有利于受压和重叠，从而减小直径。这增加了阴道分娩成功的可能性。可以通过超声检查胎儿的位置、胎位、胎方位和胎势，但胎儿头部塑形以前没有通过超声进行过研究。
本研究旨在描述在第二产程进展缓慢的初产妇人群中，通过超声评估的胎儿头部塑形情况，并研究其与胎儿位置和分娩方式的关系。
这是一项对 150 名初产妇的人群进行的二次分析，这些产妇均为头位，第二产程活跃期伴有用力。当临床医生考虑进行手术干预时，产妇符合入组标准。在存储的经会阴二维和三维采集图像中检查塑形，并根据矢状缝（中线处的塑形）将其分为顶枕部塑形、额顶部塑形和顶额部塑形（沿冠状缝的塑形）。如果位置未知，则无法对塑形进行分类，并排除这些病例。我们测量了从塑形到头部中线的距离、塑形台阶和颅骨重叠，并寻找与胎儿位置和分娩方式的关系。负责的临床医生对超声结果不知情。
排除了 6 例位置未知的病例，研究人群中共有 144 例产妇。117 例胎儿为前位，12 例为横位，15 例为后位。144 例中有 79 例（55%）观察到了塑形。在前位时，观察到的塑形明显多于非前位（69/117[59%]与 10/27[37%]；P=0.04）。在前位时，69 例为顶枕部塑形，1 例为顶额部塑形且胎头俯屈。19 例（50%）自发性分娩的前位中有塑形，71 例（59%）真空吸引分娩中有塑形，8 例（88%）真空吸引失败中有塑形（P=0.13）。4 例后位时出现顶额部塑形，3 例成功实施了真空吸引，1 例失败。2 例横位和 4 例后位出现额顶部塑形。1 例自然分娩，3 例真空吸引失败，2 例成功。11 例存在顶额部或额顶部塑形的胎儿中，仅有 1 例自然分娩。
可以通过超声对不同类型的塑形进行分类。顶枕部塑形在前位时常见，与分娩方式无显著相关性。额顶部和顶额部塑形比旧研究中报道的要少见，应在具有混合种族的更大人群中进行研究。
