This Journal Club presentation provides a summary and discussion of the following free access article published in UOG: Agreement between two- and three-dimensional transperineal ultrasound methods in assessing fetal head descent in the first stage of labor This can be accessed here: http://onlinelibrary.wiley.com/doi/10.1002/uog.9065/abstract

1. UOG Journal Club: March 2012
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
E. A. Torkildsen, K. Å. Salvesen and T. M. Eggebø
Volume 39, Issue 3, Date: March 2012, pages 310–315
Journal Club slides prepared by Dr Aly Youssef
(UOG Editor for Trainees)

2. Background
Transperineal ultrasound (TPU) can assess fetal head descent
before and during labor
The literature is sparse on this subject, and there is no agreement
regarding the superiority of 3D versus 2D ultrasound to assess fetal
head descent
Although 2D and 3D transperineal ultrasound in the labor ward are
reproducible and repeatable techniques, the intermethod agreement
between 2D and 3D techniques has not been investigated

3. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Objective: to study intraobserver repeatability and
intermethod agreement between 2D and 3D ultrasound in
assessing fetal head descent during the first stage of labor

4. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Two transperineal ultrasound (TPU) parameters
were assessed in the study
Head–perineum distance Angle of progression
(Eggebø UOG 2006) (Barbera UOG 2009)
• The shortest distance between the outer limit • The angle between the pubic symphysis
of the fetal skull and the perineum and a line tangential to the fetal skull
• Assessed in a transverse view • Assessed in a mid-sagittal view

5. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Patients and Methods
• 106 primiparous women with a live singleton term fetus in cephalic presentation and a
diagnosis of prolonged first stage were included in the study
• Women were examined in the lithotomy position, with empty bladder, after rupture of
membranes and between contractions
For each woman both the “angle of progression” and “fetal head–perineum
distance” were assessed using two different methods of acquisition
2D 3D
(one volume acquired and analyzed later 3
(3 acquisitions) times for each parameter)
• All volumes and images were obtained and stored by one operator without measured values,
and all 2D and 3D measurements were later performed by another operator blinded to clinical
assessment and labor outcome

6. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Statistical analysis
Intraobserver repeatability Intermethod agreement (2D–3D)
Was expressed as: Was performed using:
1. the difference between the highest and 1. the mean of 3 measurements for each
lowest measurements technique
2. the intraclass correlation coefficient 2. Intermethod agreement was expressed using
(ICC) the two-way random effects ICC
3. the repeatability coefficient (the range 3. Cohen’s kappa was used to assess agreement
within which two measurements by the for categorical data
same observer will fall for 95% of
subjects)
In addition, linear regression analysis was performed to investigate the
association between angle of progression and fetal head–perineum distance
(expressed using the Pearson correlation coefficient – “r”)

7. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Results: Intraobserver repeatability
Fetal head–perineum distance
2D 3D
Mean measurement (mm) 40.1 39.3
Repeatability coefficient ± 4.1 ± 1.7
(mm)
ICC (95% CI) 0.94 (0.92–0.96) 0.99 (0.99–1.00)
Angle of Progression
2D 3D
Mean measurement (º) 108.7 111.0
Repeatability coefficient (º) ± 6.7 ± 5.7
ICC (95% CI) 0.91 (0.87–0.93) 0.94 (0.91–0.96)
ICC, intraclass correlation coefficient

8. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Results: Intermethod agreement
Fetal head–perineum distance Angle of progression
ICC (95% CI) 0.95 (0.93–0.97) 0.93 (0.89–0.95)
Intermethod 95% limits -5.8 to +7.2 mm -8.9º to 13.7º
of agreement
Mean 2D–3D difference 0.7 mm 2.4º
Cohen’s kappa (95% CI) 0.85 * 0.79 †
(0.75-0.95) (0.68-0.91)
ICC, intraclass correlation coefficient
* Using 40 mm as a cut-off level
† Using 110º as a cut-off level

9. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Results: Bland–Altman plots of intermethod
agreement between 2D and 3D measurements
There was a significant, albeit small,
mean difference over the range of
the measured values for both fetal
head–perineum distance and angle
of progression.
angle of progression

10. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Results: Association between angle of progression
and fetal head–perineum distance
2D: r=−0.72
The association was significant
at the 0.01 level for both the 2D
(r=0.72) and 3D (r=0.71) scan
methods
r = Pearson correlation coefficient

11. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Discussion
• Both intraobserver repeatability and intermethod agreement between
2D and 3D acquisitions were good
• The results suggest that 2D and 3D ultrasound might be used
interchangeably in fetal head descent assessment in labor
• The intraobserver repeatability was slightly better in 3D than 2D
acquisitions
• The association between angle of progression and fetal head–
perineum distance was good for both 2D and 3D ultrasound

12. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Strength of the study
• Inclusion of a large, homogeneous and well-defined population
Weakness
• Variation in 2D measurements was analyzed using three different acquisitions,
while for 3D measurements the same acquired volume was uploaded three
times
• Possible bias due to the performance of the 3D invariably after the 2D
evaluation which might have been the reason of wider angle (mean difference
2.4º) and shorter distance (mean difference, 0.7 mm) in 3D measurements
observed in the study. However, the differences were small and probably lacking
clinical importance

13. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Conclusion
• The intraobserver repeatability and agreement between 2D and 3D
ultrasound assessment of fetal head descent in labor is good
• 2D and 3D ultrasound methods might be used interchangeably
• These results may not be applicable to the second stage of labor where
further studies are necessary

14. Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Discussion points
• What are the advantages of ultrasound over digital examination for
management of labor?
• What are the different ultrasound approaches that can be used to obtain
images of the fetal head in labor?
• What are the different ultrasound measurements that can be taken to
assess progress in labor?
• How useful are ultrasound methods in identifying fetal head position or
predicting obstructed labor?
• What do the study findings suggest would be the simplest, most
reproducible technique for assessing labor progress?

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