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Intrapartum ultrasound in women with prolonged first stage of labor

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The first stage of labor is from the start of active labor until the cervix is fully dilatated. To assess labor progress during this stage, a clinical examination has traditionally been done. The cervical dilatation, fetal head position, and fetal head station are evaluated. Moreover, these observations can be made with an ultrasound examination. Studies have shown that traditional clinical examinations are subjective, have poor reproducibility, and are unreliable. Ultrasound examinations of the fetal head station and fetal head position in the first stage of labor might predict labor outcome and mode of delivery and can help in decision making when prolonged first stage of labor is diagnosed.

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Background

Labor and delivery are divided into 3 stages: the first stage is from onset of labor to full dilatation of the cervix, the second stage is from full dilatation of the cervix to delivery of the baby, and the third stage is from the delivery of the baby to the delivery of the placenta. There is no uniform definition of the start and duration of these stages.1

The first stage of labor is divided into the latent phase, often referred to as stage 0, and the active phase. During the latent phase,

Ultrasound assessment of fetal position

Examination of the fetal position with ultrasound is feasible. This can be performed by either a transabdominal scan or a transperineal scan. When performing a transabdominal scan, the intracranial structures are used to determine the position of the fetal head. When the fetal head is at a low station, a transperineal scan is preferred. The midline angle is assessed with a transverse transperineal scan in the frontal plane related to the mother. The falx cerebri is seen as an echogenic line

Ultrasound assessment of fetal head station

The fetal head station can be examined by different TPU examinations. The angle of progression (AoP) is a sagittal transperineal scan where the angle between the long axis of the symphysis and a line joining the lower edge of the symphysis to the lower convexity of the fetal skull is measured (Figure 1).30 Head-perineum distance (HPD) is a transverse transperineal scan. The transducer is placed in the fourchette, and the soft tissue is gently compressed until a resistance is met. Furthermore,

Future perspectives

A sonopartogram has been suggested to assess labor progress. By assessing cervical dilatation, fetal head rotation, and fetal head station with ultrasound, assessing labor progress using ultrasound and reducing the number of clinical examinations have been feasible.7 These kinds of tools can help in decision making when prolonged first stage of labor occurs.

Studies have shown that TPU is well accepted by women.47,48 A randomized controlled trial where women were randomized to routine digital

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  • Cited by (4)

    • Incremental risk of clinical chorioamnionitis associated with cervical examination

      2022, American Journal of Obstetrics and Gynecology MFM
      Citation Excerpt :

      Several reports have proposed that transperineal or translabial ultrasound is an effective, feasible, and valid alternative to manual cervical examinations.18,19 Furthermore, intrapartum ultrasound performed in the first and second stage of labor may predict labor outcome and mode of delivery more accurately than traditional digital examination.20,21 However, the risk of chorioamnionitis associated with intrapartum ultrasound remains unclear, and more attention to this tool is warranted.

    • Epidural analgesia for labor: effects on length of labor and maternal and neonatal outcomes

      2023, European Review for Medical and Pharmacological Sciences
    • How to Reach the Best Ultrasound Performance in the Delivery Room

      2022, Revista Brasileira de Ginecologia e Obstetricia

    The authors report no conflict of interest.

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