UOG Journal Club: Prenatal identification of invasive placentation using ultrasound: systematic...

UOG Journal Club: November 2013Prenatal identification of invasive placentation using ultrasound:

systematic review and meta-analysis

F. D’Antonio, C. Iacovella and A. Bhide

Volume 42, Issue 5, Date: November 2013, pages 509-517

Journal Club slides prepared by Dr Leona Poon(UOG Editor for Trainees)

• Morbidly adherent placenta is associated with a significant increase in maternal morbidity (Oyelese and Smulian, 2006).

• Three major variants can be recognized according to the degree of trophoblastic invasion through the myometrium and serosa:

• Placenta accreta (most common)

• Placenta increta

• Placenta percreta

• Prenatal diagnosis of invasive placentation has been shown to reduce risk of maternal complications (Eller et al, 2009; Warshak et al, 2010).

• Ultrasound is the primary modality for prenatal diagnosis, and MRI can be complementary to ultrasound.

Oyelese Y, Smulian JC. Obstet Gynecol 2006;107;927-41.Eller AG et al. BJOG 2009;116:648-54.

Warshak CR et al. Obstet Gynecol 2010;115:65-9.

Prenatal identification of invasive placentation using ultrasound:systematic review and meta-analysis

D’Antonio et al., UOG 2013

To conduct a systematic review and meta-analysis to assess the performance of ultrasound in at-risk women for

prenatal identification of invasive placentation

Objective

• Invasive placentation was defined based on histopathological diagnosis of trophoblastic invasion, or clinical assessment of abnormal adherence at time of surgery.

• Sonographic signs included:

(1)vascular lacunae within placenta

(2)loss of normal hypoechoic retroplacental zone

(3)interruption of bladder line and/or focal exophytic masses extending into bladder space

(4)color Doppler abnormalities such as abnormal blood vessels at myometrial-bladder interface.

Methodology

Study selection



• Studies reporting a prospective diagnosis of invasive placentation and/or the evaluation of single ultrasound signs in the 2nd and 3rd trimesters.

• Studies for which the number of true +ve, false +ve, true –ve and false –ve outcomes were available.

Methodology

Eligibility criteria



• Two reviewers independently extracted data.

• Quality of studies was assessed using the revised tool for quality assessment of diagnostic accuracy studies (QUADAS-2).

Data extraction

• Meta-DiSc 1.4 was used to analyze the data.

• Heterogeneity between studies: Cochran’s Q test and I2 statistic.

• P < 0.05 and I2 > 50% indicate significant heterogeneity.

• Random or fixed effects models were used according to heterogeneity in order to pool the sensitivity, specificity, positive likelihood ratio (LR+), LR- and diagnostics odds ratio (DOR).

• ROC or summary ROC curves were plotted, AUC and the Q* index were computed to evaluate overall performance of diagnostic accuracy.

Methodology



477 potentially appropriate studies from electronic search

87 potentially appropriate studies for inclusion in meta-analysis

360 studies were excluded by reviewing the title or abstract, as they did not meet the selection criteria

23 studies (including 3707 pregnancies at risk for invasive placentation) were included in the

final analysis

64 studies were further excluded



Results

Results

Quality assessment based on QUADAS guidelines demonstrated that most studies were of high quality, low risk of bias and low concern regarding the applicability of the studies.

Summary of results of the QUADAS toolProportion of studies with low , high or unclear risk of bias (a) or concerns regarding applicability (b)



(a) (b)

Results

Forest plots of overall sensitivity and specificity of ultrasonography in the prenatal diagnosis of invasive placentation according to the current analysis



Prevalence of invasive placentation is 9.3%

ResultsPooled values for sensitivity, specificity, LR+, LR- and DOR

for overall ultrasound and the different ultrasound signs in the identification of invasive placenta

Diagnostic method

Studies(n)

Patients(n)

Sensitivity(95% CI) (%)

Specificity(95% CI) (%)

LR+(95% CI)

LR-(95% CI)

DOR(95% CI)

Ultrasound (overall) 23 3707 90.7 (87.2-93.6)

96.9 (96.3-97.5)

11.0 (6.1-20.0)

0.2 (0.1-0.2)

98.6 (48.8-199.0)

Placenta lacunae 13 2725 77.4 (70.9-83.1)

95.0 (94.1-95.8)

4.5 (2.5-8.1)

0.3 (0.2-0.4)

24.3 (9.1-64.8)

Loss of hypoechoic space

10 2633 66.2 (58.3-73.6)

95.8 (94.9-96.5)

5.6 (2.3-14.1)

0.4 (0.2-0.7)

22.0 (6.8-70.6)

Abnormalities of uterus-bladder interface

9 2579 49.7 (41.4-58.0)

99.8 (99.5-99.9)

30.6 (8.1-115.5)

0.5 (0.3-0.8)

93.7 (35.5-247.5)

Color Doppler abnormalities

12 714 90.7 (85.2-94.7)

87.7 (84.6-90.4)

7.8 (3.3-18.4)

0.2 (0.1-0.3)

69.0 (22.8-208.9)



ResultssROC curves of placental lacunae (blue), loss of retroplacental clear space (green), bladder-border abnormalities (yellow) and

color-Doppler abnormalities (red) in prenatal diagnosis of invasive placentation.



Among the different ultrasound signs, color Doppler had the best predictive accuracy:

• Sensitivity 90.7% (95%CI 85.2-94.7)• Specificity 87.7% (95%CI 84.6-90.4)

• LR+ 7.77 (95%CI 3.3-18.4) • LR- 0.17 (95%CI 0.10-0.29)

• DOR 69.02 (95%CI 22.8-208.9)

• Prenatal ultrasound has high predictive accuracy in diagnosing invasive placentation in women at high risk.

• Among the sonographic signs of invasive placentation, color Doppler had the best combination of sensitivity and specificity.

• Assessment of individual signs should be viewed with caution.

• Observation of one sign is likely to increase the chance of detecting others, since the signs are not looked for in isolation.

• The authors hypothesize that:• A reduction in the number of sonographic criteria for invasive placentation may

increase sensitivity but is likely to reduce specificity.

• An increase in the number of sonographic criteria for invasive placentation would reduce sensitivity but would improve specificity.

Discussion



• The low sensitivity of placental lacunae may arise because the lower uterine segment appears as a thin line during the late 3rd trimester on conventional transabdominal ultrasound, so evaluation of the interface between the myometrium and the placenta may be difficult.

• Higher degrees of placental invasion lead to penetration of the bladder. This condition may be diagnosed with ultrasound by examining the border between the bladder and myometrium, which is normally echogenic and smooth.

• Exophytic masses in the bladder are likely to be seen only with placenta percreta – this observation is a reliable ‘rule-in’ sign but its absence does not exclude lesser degrees of placental adherence.

Discussion



1. Some reported series were prospectively conducted but ultrasound signs were retrospectively examined. With the benefit of hindsight, it might have been easier to spot signs in images on prenatal ultrasound.

2. Results from this review are only applicable to women with anterior placenta praevia and a history of a Cesarean delivery or uterine surgery, but not applicable to women with fundal or posterior placenta with invasive placentation.

3. Abnormalities on color Doppler and presence of abnormal vessels performed best as predictors of disorders of invasive placentation in high risk women. However, this is not an objective criterion.

Limitations



• Among the different ultrasound signs, the presence of abnormal vasculature on color Doppler ultrasound has the best combination of sensitivity and specificity.

• Abnormality of the uterus-bladder interface has the best specificity.

• The presence of placental lacunae and loss of the clear space between the placenta and myometrium do not perform as well.

• In women with a low anterior placenta who have had uterine surgery, 3rd trimester ultrasound is highly sensitive and specific in diagnosing invasive placentation prenatally.

• Future research should be directed at developing objective criteria for color Doppler abnormalities and for determining the best surgical technique for delivery.

Conclusions



Discussion points

• Is there a need to set up a multi-disciplinary clinic for the prenatal diagnosis and subsequent management of invasive placentation?

• If yes, should all women with an anterior low-lying placenta and previous history of Cesarean delivery or uterine surgery be referred to this clinic?

• How should we develop the objective criteria for the diagnosis of invasive placentation (i.e. color Doppler abnormalities), thus allowing objective structured training of fetal medicine subspecialists?



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