ultrasound in labor and delivery -...

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


“Angle of Progression”


symphysis

head contour

Fetal Head Caput

Trans Perineal Ultrasound

caput

103o

Fetal Head:“Angle of Progression”


Fetal Head:“Angle of PProgression”


Fetal Head:“Angle of Progression”


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

ultrasound in labor and delivery -...

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