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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 33  |  Issue : 2  |  Page : 487-491

Intrapartum ultrasound to predict vaginal labor in primigravida


1 Department of Obstetrics and Gynecology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Obstetrics and Gynecology, Om El-Masryeen General Hospital, Giza, Egypt

Date of Submission12-Aug-2019
Date of Decision01-Sep-2019
Date of Acceptance06-Sep-2019
Date of Web Publication27-Jun-2020

Correspondence Address:
Shady M. S. Amin
Gamal Abd El Nasr Street, Shebin El Kom, Menoufia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_250_19

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  Abstract 

Objectives
To evaluate head–perineum distance (HPD) and angle of progression (AOP) as predictors of successful vaginal delivery in the active phase of first stage of labor in primigravida.
Background
Intrapartum ultrasonography has enabled further understanding of the complex physiology of childbirth. It has been shown to provide objective information on the dynamics of different stages of labor and may also be used to assess the mode of delivery.
Patients and methods
This prospective cohort study was conducted at obstetrics departments of Om El-Masryeen General Hospital, Giza, Egypt, from November 2018 to March 2019. This study included 80 pregnant women in the active phase of first stage of labor who fulfilled inclusion and exclusion criteria. Full history taking, physical and local examination, and obstetric ultrasound were done, and transperineal ultrasound was done to measure HPD and AOP.
Results
Women who delivered vaginally showed a statistically significant higher mean of the AOP (120.3 ± 11.9°) versus who delivered by cesarean section (89.1 ± 10.7°), with aP value of 0.001. At a cutoff of more than 104°, AOP predicted successful vaginal labor, with a sensitivity of ~90% and a specificity of 86%. At cutoff less than 4.5 cm, HPD predicted successful vaginal labor with a sensitivity of ~88% and a specificity of 91%.
Conclusion
Transperineal ultrasound measurement of HPD and AOP in the first stage of labor accurately predicts the mode of delivery.

Keywords: Intrapartum, labor, predict, primigravida, ultrasound


How to cite this article:
Kandil MA, Elhalaby AE, Ammar HA, Anter ME, Amin SM. Intrapartum ultrasound to predict vaginal labor in primigravida. Menoufia Med J 2020;33:487-91

How to cite this URL:
Kandil MA, Elhalaby AE, Ammar HA, Anter ME, Amin SM. Intrapartum ultrasound to predict vaginal labor in primigravida. Menoufia Med J [serial online] 2020 [cited 2020 Dec 5];33:487-91. Available from: http://www.mmj.eg.net/text.asp?2020/33/2/487/287766




  Introduction Top


The current obstetric practice strives to avoid difficult vaginal deliveries; although being the 'gold standard' for obstetric practice, digital transvaginal examination is a subjective evaluation based on the clinician's skill, with several limitations[1]. Women in active labor are clinically assessed to determine cervical dilation and fetal station by regular digital vaginal examinations (DVEs). DVEs have been deemed unreliable and subjective and have failed to determine the fetal head position in 34% of laboring women, and have incorrectly determined head position in 51% of patients in whom the position could be defined[2],[3]. DVEs are shown to be associated with infection ascending to the fetus, chorioamnionitis, endometritis, and shortened time interval to delivery in preterm labor and are painful and embarrassing to the women being examined[4],[5]. Intrapartum ultrasonography has enabled further understanding of the complex physiology of childbirth. It has been shown to provide objective information on the dynamics of different stages of labor and may also be used to assess the prognosis for operative vaginal delivery[6]. On transperineal imaging in the midsagittal plane, several parameters have been proposed that use the pubic symphysis as landmark and reference point for quantitative measurements. Three parameters indicate head station directly: the angle of progression (AOP), the progression distance, and the transperineal ultrasound head station. Others indicate it indirectly: the head–symphysis distance (HSD) is an indirect parameter that changes with descent, and the head direction indicates the direction of the longest recognizable axis of the fetal head with respect to the long axis of the pubic symphysis. With simple clockwise rotation of the transducer by 90°, an axial plane is obtained, in which two additional parameters can be evaluated and measured: the head–perineum distance (HPD), as a marker of head station, and the midline angle, which assesses rotation of the head[7]. The HPD is measured by calculating the shortest distance from the perineal skin surface to the outmost bony limit of the fetal skull in a transverse view. A shorter HPD was significantly associated with shorter time to delivery, fewer cesarean deliveries, and decreased use of epidural analgesia. This parameter is easy to measure even by nonexperts and is relatively safe for women with membrane rupture[8]. AOP is described as the angle between a line through the midline of the pubic symphysis and a line from the inferior apex of the symphysis to the leading part of the fetal skull[3]. Some authors concluded that the measurement of the AOP on intrapartum ultrasound imaging is reliable regardless of fetal head station or the clinician's level of ultrasound experience[1]. Intrapartum ultrasound imaging might allow the dynamic assessment of the progress of labor with prognostic potentials and provides a more scientific basis for assessing labor[9]. The aim of this study was to evaluate HPD and AOP as predictors of successful vaginal delivery in the active phase of first stage of labor in primigravida.


  Patients and Methods Top


This prospective cohort study was conducted at Obstetrics Departments of Om El-Masryeen General Hospital, Giza, Egypt, from November 2018 to March 2019, after obtaining an approval from Hospital Local Medical Ethics Committee, and an informed consent was obtained from all study participants after explanation of the nature and scope of the study. The study was done on 80 pregnant women. The selected cases fulfilled the following: inclusion criteria: primigravida with singleton viable cephalic (vertex) fetus at gestational age 37–40 weeks in active phase of first stage of labor, and exclusion criteria: multiple pregnancy, fetal malpresentation, macrosomia detected by ultrasound, induced labor, and obstetric indication for cesarean section (CS), for example, cephalopelvic disproportion, fetal distress, etc., The active phase of labor was diagnosed by onset of regular rhythmic uterine contractions and cervical dilatation beyond 4 cm. Obstetric history was taken, and complete general and local obstetric examination was done followed by obstetrical ultrasound to determine gestational age, fetal presentation, fetal position, and estimated fetal weight. Transperineal ultrasound was done to measure HPD and AOP by using Mindray Ultrasound device, Dp-20 (Guangzhou Happycare Electronics Co. Ltd, Guangzhou, China). The measurements were done in the lithotomy position with an empty bladder. The ultrasound transducer was covered with gel, and a sterile glove was used to firmly press the labia majora when obtaining the measurements. To measure HPD, the transducer was held in a transverse plane on the vulva at the level of the posterior commissure and pressed against the pubic rami, and the distance from the fetal head to the perineum was measured and recorded. AOP was measured in the sagittal plane, by drawing a line through the long axis of the symphysis and another line tangential to the fetal head and measuring the angle in between the two lines. Sample size was calculated by using PASS, version 11 (NCSS LLC, Kaysville, Utah, USA), according to Ingeberg et al.[10]; at ∝ error of 0.05 and study power of 80%, a total sample size of 80 participants was found to be convenient to fulfill the aim of the work of this study.

Statistical analysis

Results were collected, tabulated, and statistically analyzed by an IBM compatible personal computer with SPSS statistical package version 20 (SPSS Inc. released 2011. IBM SPSS statistics for Windows, version 20.0, IBM Corp., Armonk, New York, USA). Quantitative data were expressed as mean ± SD, whereas qualitative data were expressed as numbers and percentages. Mann–Whitney test (U), which is a test of significance, was used to test parameters. A P value less than 0.05 was considered statistically significant. Receiver operating characteristic (ROC) curve was used to compute the area under the curve as a discriminator. The area under the curve was considered to have discriminatory potential if the lower limit of the 95% confidence interval (CI) exceeded 0.5, which was used to identify a cutoff value for HPD and AOP to detect successful vaginal delivery. Data were analyzed and appropriately presented in tables and figures.


  Results Top


This study included 80 women in active phase of first stage of labor who fulfilled the inclusion and exclusion criteria. They were divided into two groups according to the mode of delivery: 58 women delivered vaginally and 22 delivered by CS. The indication of CS was owing to failure to progress. There were no significant statistical differences between the group that delivered vaginally and group that delivered by CS according to maternal age, gestational age, BMI, and estimated fetal weight (P = 0.068, 0.116, 0.834, and 0.514, respectively) [Table 1]. Women who delivered vaginally showed a statistical significance higher mean of the AOP (120.3 ± 11.9°) versus who delivered by CS (89.1 ± 10.7°) with a P value of 0.001. The mean HPD was 3.8 ± 0.63 cm in the women delivering vaginally versus 5.04 ± 0.48 cm in the women delivering by CS (Mann–Whitney U = 35.0; P < 0.001) [Table 2]. ROC curve of HPD for predication of vaginal delivery ([Table 3], and [Figure 1]) showed at cutoff less than 4.5 cm, HPD correctly identified cases that successfully delivered vaginally with a sensitivity of ~88% and a specificity of 91%. ROC curve of AOP for predication of vaginal delivery ([Table 3], and [Figure 2]) showed at cutoff more than 104°, AOP correctly identified cases that successfully delivered vaginally with a sensitivity of ~90% and a specificity of 86%.
Table 1: Demographical characteristics of the study participants

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Table 2: Angle of progression and head-perineum distance among the study participants

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Table 3: Receiver operating characteristic curve of head-perineum distance and angle of progression for predication of vaginal delivery

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Figure 1: Receiver operating characteristics curve for head–perineum distance in primigravida women in the active phase of first stage of labor in the prediction of vaginal delivery (area under the curve = 0.917,P < 0.001).

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Figure 2: Receiver operating characteristics curve for angle of progression in primigravida women in the active phase of first stage of labor in the prediction of vaginal delivery.

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  Discussion Top


Transperineal ultrasound measurements of HPD and AOP in the first stage of labor contributes clinically significant information about the chance for vaginal labor outcome in nulliparous women. The AOP was wider in cases who delivered vaginally than those delivered by CS; at cutoff more than 104°, AOP correctly identified cases that successfully delivered vaginally with a sensitivity of ~90% and a specificity of 86%. HPD was shorter in cases that delivered vaginally than those that delivered by CS; at cutoff less than 4.5 cm, HPD correctly identified cases that successfully delivered vaginally with a sensitivity of ~88% and a specificity of 91%. The results of current study are in agreement with Ingeberg et al.[10], who found a strong relationship between the AOP and mode of delivery. AOP more than or equal to 105° was predictive of successful vaginal delivery. HPD was less than or equal to 40 mm in 18 women, of whom all delivered vaginally. HPD was more than 40 mm in the other 18 women, of whom eight delivered vaginally. The differences between these results and our study results may be owing to the way of measurement, as the transducer is placed in the posterior fourchette and pressed firmly against the pubic bone, and there might be variation of HPD with BMI. In other studies, Eggebø et al.[11] concluded that AOP more than or equal to 110° is a predictor for successful vaginal delivery, Barbera et al.[12] showed that an AOP of at least 120° was always associated with spontaneous vaginal, and Silvia et al.[13] concluded that angle more than or equal to 125° is a predictor for successful vaginal delivery; this range of 20° difference may be owing to interobserver variation. Torkildsen et.al.[14] conducted a prospective observational study on 110 primiparous women with singleton cephalic presentation at term diagnosed with prolonged first stage of labor. Induction of labor was done in 17 cases. Augmentation during labor was done in 108 cases. Mode of delivery was 25.5% (28/110) CS, 41.8% (46/110) operative vaginal delivery, and 32.7% (36/110) spontaneous vaginal delivery. Indications for CS were prolonged first stage (n = 20), prolonged second stage (n = 4), and fetal distress (n = 4). Indications for operative vaginal delivery were prolonged second stage (n = 25) and fetal distress (n = 21). In 48% of women, the AOP was more than or equal to 110° and 87% (95% CI, 75–93%) of them delivered vaginally versus 38% (95% CI, 21–57%) with angle less than 100°. In present study, we have not recorded operative vaginal delivery. Moreover, we have not recorded any induction or augmentation of labor. Levy et.al.[15]in their prospective, observational study included 171 women who met the inclusion criteria, where 100 were nulliparous and 71 were parous. Among the 100 nulliparous women, the median AOP before onset of labor was narrower in those who went on to deliver by CS (n = 9) than in those delivered vaginally (n = 91) (90° vs. 104°), P value less than 0.001; an AOP more than or equal to 95° was associated with vaginal delivery in 99% of women, and 89% of women who delivered by CS had an AOP less than 95°. Among the 71 parous women, only one delivered by CS, and all of those with an AOP less than 95° delivered vaginally. The fact that the AOP in this study was measured before the onset of labor and included both nulliparous and parous unlike the present study may be the reason why these measurements are different than the present study.

The present study indicates that intrapartum ultrasound may assist doctors and midwives in predicting labor outcome. If intrapartum ultrasound measurements made in the first stage of labor are successfully implemented into clinical practice, this patient group may benefit from a reduced number of medical interventions and the prompt initiation of medical interventions when they are required, with the prospect of reducing maternal and fetal morbidity and mortality.

This study had some limitations, such as we only included primigravida women and the relative small sample size. Further studies are needed on the predictive and implementable value of transperineal ultrasound in influencing clinical decision making.


  Conclusion Top


Transperineal ultrasound measurements of HPD and AOP in the first stage of labor accurately predict the mode of delivery. At cutoff more than 104°, AOP correctly identified cases that successfully delivered vaginally with a sensitivity of ~90% and a specificity of 86%. At cutoff less than 4.5 cm, HPD correctly identified cases that successfully delivered vaginally with a sensitivity of ~88% and a specificity of 91%.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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