Imaging
Sonographic detection of placenta accreta in the second and third trimesters of pregnancy

https://doi.org/10.1016/j.ajog.2003.11.024Get rights and content

Abstract

Objective

The purpose of this study was to determine whether ultrasonography can detect placenta accreta reliably in at-risk patients.

Study design

All patients with a previous cesarean delivery and an anterior placenta or placenta previa were evaluated prospectively at each visit for sonographic signs of placenta accreta (interruption of the posterior bladder wall–uterine interface, absence of the retroplacental clear zone, and placental lacunae).

Results

This evaluation involved 2002 patients over a 12-year period. Of the 14 patients with a confirmed diagnosis of placenta accreta who had ultrasound examinations between 15 and 20 weeks of gestation, the diagnosis was suspected strongly in 86% of the patients (12/14 patients). There were 18 false-positive cases (54.5%; 18/33 patients), most of which were due to a lack of visualization of the echolucent area between the placenta and the myometrium (obliteration of the ‘clear space’) during the third trimester. The presence of multiple linear irregular vascular spaces within the placenta (placental lacunae) was the diagnostic sign with the highest positive predictive value for placenta accreta.

Conclusion

Placenta accreta can be detected as early as 15 to 20 weeks of gestation in most at-risk patients by visualization of irregular vascular spaces within the placenta (placental lacunae). Obliteration of the retroplacental ‘clear space’ is not a reliable diagnostic sign for placenta accreta.

Section snippets

Methods

Prospectively, all patients who were seen for a fetal ultrasound examination between March 1990 (when an electronic database was adopted) and August 2002 were asked whether they had ever had a cesarean delivery. If the answer was affirmative, a sonographic examination was performed over the area of the presumed uterine scar to determine whether there were any sonographic signs of placenta accreta. This study was exempted from review by the William Beaumont Institutional Review Board.

Scans were

Results

Over the 12 years of the study period, 163,855 obstetrics examinations were performed in our unit. Of these, 2002 patients had dual risk factors of a history of a previous cesarean delivery, along with the ultrasound finding of either a placenta previa or low anterior placenta (lower edge <2 cm from the internal os). In 33 of these 2002 cases, ultrasound findings that were suspicious for a placenta accreta were noted on at least 1 scan (1.6%). These 33 cases form the basis of our study on the

Comment

The findings of this study supplement our earlier report that showed an association of a low gestational sac that was seen on first trimester scans for patients with placenta accreta.7

Discussion

We found that obliteration of the clear space can develop over the course of pregnancy but that the clear space alone is not a good diagnostic sign for placenta accreta. Visualization of placental lacunae was the most reliable diagnostic sign. In addition, we found lacunae as early as 15 weeks of gestation in most patients who were examined then. This is a noteworthy finding because mid second trimester is the time at which most patients have their “screening” ultrasound examination. Only 3 of

Supplementary Files

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