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The use of ultrasound on the labor and delivery
suite
The menu of quick hits
1. Cervical length and threatened pre-term labor
2. Premature rupture of membranes
3. Placenta previa before delivery
4. Vasa previa
5. Uterine scar
6. Trans-perineal ultrasound (TPU)
Patients who present in Preterm labor
Most patients presenting with contractions in late pregnancy prior to 36 weeks are in PTL
Our job is to pick out the ones who are really at risk and leave the others alone.
Cervical Length
A key to preterm labor
Cervical LengthTsoi E, et al. Ultrasound Obstet Gynecol 2003; 21 (6): 552-555
216 pts with painful preterm contractions (24-36 wks)
43 pts – cervical length <1.5 cm
16 of these (37%) delivery < 7 days
However, 132 had CL > 1.5 cm and only one delivered with 7 days
Negative predictive value of > 99%
Cervical Length in Preterm Labor
253 women with preterm labor21 delivered preterm (8.3%)
If CL ≥ 1.5 cm, 1.8% delivered 7 days
If CL 1.5 cm, 47.2% delivered 7 days
Fuchs IB, et al. Ultrasound Obstet Gynecol 2004; 24: 554-447
Cervical Length
Proof from RCT that CL is useful
RCT 3 studies
287 patients between 27 and 35 weeks with regular contractions
In half the providers were provided with the cervical length information, half not.
Those CL patients had a 36% drop in PTB < 37 weeks and 10% fewer interventions.
Berghella etal Ultrasound Obstet Gynecol. 2017; 49: 322-29
Suggested Protocol in ThreatenedPTL
If Cl < 2 cm, admit
If CL 2.0 cm- 2.9, get fFN. If positive, admit
If 3.0 cm or more, discharge
PROM. Are the membranes actually
ruptured?
Intact Membranes
Ruptured Membranes
Cervical Length and pPROM
101 women with pPROM58 delivered within 7 days
Highly correlated with: cervical length
presence or absence of contractions
gestational age
Tsoi E, et al. Ultrasound Obstet Gynecol 2004;24: 550-553
Cervical Length and pPROM: Revisited
Tsoi E, et al. Ultrasound Obstet Gynecol 2004; 24: 550-553
Relationship betweencervical length and
incidence of deliverywithin 7 days of
ROM
“Nobody likes surprises. Placenta
previa should not be one of them”Confucius or Tolstoy, or someone smart
Placenta Previa
CSR Bleeding before delivery
If placenta 10 – 22 mm away 31% 3%
If placenta 1 – 10 mm away 75% 29%
No difference in blood loss at delivery or postpartum hemorrhage
Vergani P, et al. Am J Obstet Gynecol 2009; 201: 266.e1-6
Transvaginal Surprise
Incidence – 1 : 2500
Risk Factors Multiple pregnancies
2nd trimester low-lying placenta
IVF
Bleeding
Bi-lobed / Succenturiate lobed placenta
IVF 1 in 290
Types (1) Velamentous cord insertion
(2) Succenturiate placenta
Mortality – 70-90%-- if not diagnosed!
Vasa Previa
Vasa previa: Knowing it is there is lifesaving
The point(s)?
Some time before delivery, make sure there is only one placenta.
Always look for the placental cord insertion
Also, if the placenta is low lying, and Cesarean section is in the offing, make sure the cord insertion is not on a collision pathway with the scalpel.
A TOLAC: To have or not to have?
Depends upon the thickness of the
scar.Shakespeare, William AJOG 1594; 2: 21-22.
Uterine Scar
First study: Uterine Wall ScarsLancet 1996; 347: 281-284
Ultrasound and uterine wall scars
642 patients with previous C-sections
All had TA ultrasound evaluation of lower uterine segment (one investigator in all)
Vaginal delivery 60.1%
CSx (1/2 emergency) 39.9%
Uterine rupture 2.5%
Dehiscence 1.5%
Uterine Wall ScarsLancet 1996; 347: 281-284
ConclusionIf thinnest uterine wall diameter is > 3.5 mm, negative predictive value was 99.3%
16% of those with 1.6 – 2.5 mm had scar defect
Safe to do VBAC if uterine wall is of adequate thickness
Uterine wall thickness and rupture: a review
Labor in previous pregnancy increases the thickness of scar in next pregnancy. (by average of 0.6mm).
Previous studies:
1. Bujold (2009) 236 pts. 2.3 mm threshold. 9.1% vs 0% rupture
2. Gotoh (2000) 2.0 mm threshold. PPV 73.9%, NPV 100%.
Studies vary but:
If > 3.5 mm chances of rupture or dehiscence close to 0%
If < 2.5 mm chances were high (up to 16%).
Between 2.5 mm and 3.5 mm, risk varied enough to make predictions difficult
Uterine Scar ThicknessPaper from MontrealLogistic regression analysis for factors that were associated with uterine scar defect
Before Adjustment After Adjustment
Factors Odds Ratio 95% CI Odds Ratio 95% CI
Full lower uterinesegment thickness <2.3 mm
5.09 1.24 – 20.98 4.6 1.04 – 20.91
Single-layer closure 5.79 1.48 – 22.65 6.54 1.39 – 30.82
Inter-delivery interval, mo
< 18 6.79 1.49 – 31.03 9.74 1.57 – 60.57
18 – 24 1.21 0.14 – 10.69 1.32 0.14 – 12.86
≥ 24 1.00 -- 1.00 --
CI, confidence intervalBujold E, et al. Am J Obstet Gynecol 2009; 201: 320.e1-6
Techniques to do uterine scar
thickness
Ways to approach the uterine wallTAS: This works best in patients who have not had labor before prior CSx or whose section was performed preterm.
TVS: Best if term delivery with labor prior to previous CSx.
Ideal to use both
Can third‐trimester assessment of uterine scar in women with prior Cesarean section predict uterine rupture?
Ultrasound in Obstetrics & GynecologyVolume 47, Issue 4, pages 410-414, 6 APR 2016 DOI: 10.1002/uog.15786http://onlinelibrary.wiley.com/doi/10.1002/uog.15786/full#uog15786-fig-0001
Trans-perineal Ultrasound
Fetal station and progression through labor
Work of Antonio Barbera and later authors
Indications for Cesarean Section
NRFHR 21.9%
Failure to progress 20.7%
Pelvic Landmark
Ischial Spines
Fetal Head StationClinical Assessment
Friedman 1978
Pelvic Axis
axis ofthe inlet
axis ofthe outlet
Pelvic Axis
Angle of ischial spinesCT scan identification
98o.2
Angle of progression
13
42
5
-5-4 -3
-2-1
Geometrical Model
Trans Perineal UltrasoundTechnique
Trans Perineal UltrasoundTechnique
“Angle of Progression”
Trans Perineal UltrasoundTechnique
symphysis
head contour
Fetal Head Caput
Trans Perineal Ultrasound
caput
103o
Fetal Head:“Angle of Progression”
Trans Perineal Ultrasound
Fetal Head:“Angle of PProgression”
Trans Perineal Ultrasound
Fetal Head:“Angle of Progression”
Trans Perineal Ultrasound
Angle of progressionGeometrical Model
Station Angle
-5 65
-4 71
-3 78
-2 85
-1 91
0 98
1 105
2 112
3 119
4 126
5 133
Some controversy regarding TPU angle and clinical station
Tutschek et al, correspondence in Ultrasound Gynecol 2017;49:279
0 station on CT equaled TPU angle of 116°(versus 98°)
+1 station was 127°(versus 105°)
Big difference between the objective CT studies. This now makes it difficult to compare angle with our conception of clinical station.
What we do know about the TPU angle.
1. TPU angle has excellent inter-observer variability
Digital exam is a crap shoot with awful IOV
2. TPU can be used objectively to follow progress using the head as its own control.
3. It correlates with : ultimate ability to attain vaginal delivery (threshold >125° – 160°), length of second stage* (>125°), success of induction** (90°before induction), and success of vacuum delivery (145°).
*Ghi et al AJOG 2016;215: 214
** Baltez et al UOG 2016;48: 36-91.
***Gillor et al UOG 2017;49:290.
Other techniques with TPU
Prediction of time to delivery by transperineal ultrasound in second stage of labor
Ultrasound in Obstetrics & GynecologyVolume 49, Issue 2, pages 246-251, 7 FEB 2017 DOI: 10.1002/uog.15944http://onlinelibrary.wiley.com/doi/10.1002/uog.15944/full#uog15944-fig-0002
Prediction of time to delivery by transperineal ultrasound in second stage of labor
Ultrasound in Obstetrics & GynecologyVolume 49, Issue 2, pages 246-251, 7 FEB 2017 DOI: 10.1002/uog.15944http://onlinelibrary.wiley.com/doi/10.1002/uog.15944/full#uog15944-fig-0001
Figure 1The technique for the measurement of the occiput spine angle by means of transabdominal ultrasoundImage devised by Tullio Ghi, MD, University of Parma, and drawn by Simona Morselli, graphic designer, Bologna, Italy.Ghi et al. A new sonographic parameter to diagnose fetal head deflexion. Am J Obstet Gynecol 2016 .
Narrow subpubic arch angle is associated with higher risk of persistent occiput posterior position at delivery
Ultrasound in Obstetrics & GynecologyVolume 48, Issue 4, pages 511-515, 25 AUG 2016 DOI: 10.1002/uog.15808http://onlinelibrary.wiley.com/doi/10.1002/uog.15808/full#uog15808-fig-0001
Sub pubic arch
339 patients at term had 3 D acquisitions by TPU
At delivery; 92% delivered from an OA position, 8% OP
Average SPA was 104°in OP, compared with average SPA in OA of 116.4°
Maternal height also correlated statistically with OP.
The best SPA cut off for OP at delivery was < 90.5°.
Also much higher rate of CSx and instrument delivery
Ghi et al UOG 2016; 48: 511-515.
A parting thought
Even an old hand-me-down machine nearby can give all the information you need to answer some of the most important questions that arise on the labor and delivery floor.
All one needs is the creativity and motivation to use it.
But here is a dissenting voice