Fetal molding examined with transperineal ultrasound and associations with position and delivery mode

Iversen, J.K.; Kahrs, B.H.; Torkildsen, E.; Eggebø, Torbjørn Moe

doi:10.1016/j.ajog.2020.06.042

“…The skull bones overlap during the passage through the birth canal and the fetal head becomes molded. 66 Because of molding, the leading bony part of the skull may be HSD, head-symphysis distance.…”

Section: Head-symphysis Distancementioning

confidence: 99%

Descent of the presenting part assessed with ultrasound

Eggebø

¹

,

Hjartardóttir

²

2024

American Journal of Obstetrics and Gynecology

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Fetal head descent can be expressed as fetal station and engagement. Station is traditionally based on clinical vaginal examination of the distal part of the fetal skull and related to the level of the ischial spines. Engagement is based on a transabdominal examination of the proximal part of the fetal head above the pelvic inlet. Clinical examinations are subjective, and objective measurements of descent are warranted. Ultrasound is a feasible diagnostic tool in labor, and fetal lie, station, position, presentation, and attitude can be examined. This review presents an overview of fetal descent examined with ultrasound. Ultrasound was first introduced for examining fetal descent in 1977. The distance from the sacral tip to the fetal skull was measured with A-mode ultrasound, but more convenient transperineal methods have since been published. Of those, progression distance, angle of progression, and head-symphysis distance are examined in the sagittal plane, using the inferior part of the symphysis pubis as reference point. Head-perineum distance is measured in the frontal plane (transverse transperineal scan) as the shortest distance from perineum to the fetal skull, representing the remaining part of the birth canal for the fetus to pass. At high stations, the fetal head is directed downward, followed with a horizontal and then an upward direction when the fetus descends in the birth canal and deflexes the head. Head descent may be assessed transabdominally with ultrasound and measured as the suprapubic descent angle. Many observational studies have shown that fetal descent assessed with ultrasound can predict labor outcome before induction of labor, as an admission test, and during the first and second stage of labor. Labor progress can also be examined longitudinally. The International Society of Ultrasound in Obstetrics and Gynecology recommends using ultrasound in women with prolonged or arrested first or second stage of labor, when malpositions or malpresentations are suspected, and before an operative vaginal delivery. One single ultrasound parameter cannot tell for sure whether an instrumental delivery is going to be successful. Information about station and position is a prerequisite, but head direction, presentation, and attitude also should be considered.

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“…10,24 Reshaping of the fetal skull is possible because the skull bones can overlap. 11 During this process the fetal head gets elongated with increased longitudinal diameter and reduced transverse diameter, increasing the probability of a vaginal delivery. 25 We found longer heads in fetuses in active labor than those examined before the start of active phase.…”

Section: Clinical Significancementioning

confidence: 99%

“…In flexed occiput anterior (OA) position, fetal head engagement occurrs when the leading bony part of the skull is at the level of the ischial spines. 7e9 In malpositions and molded (reshaped) fetal heads, the leading bony part of the skull may be below the ischial spines when the largest diameter of the fetal skull is still above the pelvic inlet, 10,11 An attempt at assisted vaginal birth in such a situation would be associated with risks of maternal and neonatal complications, and therefore, contraindicated in modern obstetrics. To avoid this mismanagement, a vaginal or transperineal assessment of fetal head descent should be supplemented with abdominal examination, as recommended in several guidelines and the World Health Organization partograph.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Fetal head descent assessed by transabdominal ultrasound: a prospective observational study

Kamel

¹

,

Negm

²

,

Kahrs³

et al. 2022

American Journal of Obstetrics and Gynecology

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BACKGROUND: Determining fetal head descent, expressed as fetal head station and engagement is an essential part of monitoring progression in labor. Assessing fetal head station is based on the distal part of the fetal skull, whereas assessing engagement is based on the proximal part. Prerequisites for assisted vaginal birth are that the fetal head should be engaged and its lowermost part at or below the level of the ischial spines. The part of the fetal head above the pelvic inlet reflects the true descent of the largest diameter of the skull. In molded (reshaped) fetal heads, the leading bony part of the skull may be below the ischial spines while the largest diameter of the fetal skull still remains above the pelvic inlet. An attempt at assisted vaginal birth in such a situation would be associated with risks. Therefore, the vaginal or transperineal assessments of station should be supplemented with a transabdominal examination. We suggest a method for the assessment of fetal head descent with transabdominal ultrasound. OBJECTIVE: To investigate the correlation between transabdominal and transperineal assessment of fetal head descent, and to study fetal head shape at different labor stages and head positions. STUDY DESIGN: Women with term singleton cephalic pregnancies admitted to the labor ward for induction of labor or in spontaneous labor, at

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“…Active management of labor dystocia typically includes calculating adequacy of uterine contractions using Montevideo units (MVUs) measured via an intrauterine pressure catheter [ 2 ]. Studies have found that the inclination of the pelvis and uterus in the birth canal is also an influential factor in dystocia [ 3 ]. Uterine inclination is an important factor for birth canals and fetuses in vaginal delivery [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

Manipulative Reduction for Abnormal Uterine Inclination in Vaginal Delivery

Chen

¹

,

Yuan

²

,

Wang

³

2022

Computational and Mathematical Methods in Medicine

0

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Objective. To investigate the manipulative reduction in abnormal uterine inclination in vaginal delivery. Methods. With the independently developed uterine inclination surveyor, 40 primiparas with abnormal uterine inclination were randomly divided into two groups: treatment group (Group A, 20 cases) and control group (Group B, 20 cases). The general condition of the primipara, the labor stages, the changes in uterine inclination after treatment, postpartum hemorrhage at 2 hours, and the general condition of fetuses were observed to study the therapeutic value of manual reduction in abnormal uterine inclination. Result. In the control group, one uterine inclination was not corrected with the change in labor process, and the pregnancy was terminated due to stagnation of the active phase. In the first stage of labor, the time spent in the treatment group ( 393.4 ± 31.3 mins) was significantly lower than that in the control group ( 440.7 ± 34.9 mins) ( P = 0.001 ). Compared with the control group ( 49.8 ± 6.5 mins), the treatment group ( 42.6 ± 7.2 mins) also exhibited a significantly shortened second stage of labor ( P = 0.02 ). Sixteen cases (16/20) in the treatment group returned to normal after manual reduction, and 9 cases (9/20) in the control group returned to normal with the progression of natural labor. Manual reduction could be used as an option to treat abnormal uterine inclination ( P = 0.01 ). There was no significant difference in the third stage of labor ( P = 0.2 ), 2-hour postpartum hemorrhage ( P = 0.35 ), Apgar score ( P = 0.64 ), or body weight ( P = 0.76 ) between the two groups. Conclusion. Manual reduction in the treatment of abnormal uterine inclination has obvious effects, shortens the birth process, and is safe for the fetus.

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Fetal molding examined with transperineal ultrasound and associations with position and delivery mode

Cited by 9 publications

References 44 publications

Descent of the presenting part assessed with ultrasound

Descent of the presenting part assessed with ultrasound

Fetal head descent assessed by transabdominal ultrasound: a prospective observational study

Manipulative Reduction for Abnormal Uterine Inclination in Vaginal Delivery

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