Another look at ultrasound and magnetic resonance imaging for diagnosis of placenta accreta.

OBJECTIVE: To compare the ability of magnetic resonance imaging (MRI) and ultrasound (US) in the diagnosis of placenta accreta, to examine the success of various sonographic and MRI features to correctly predict invasive placenta, and to define a specific role for MRI in placenta accreta. METHODS: After Institutional Review Board approval, a blinded retrospective review was undertaken of US and MRI findings from 45 patients who had an obstetrical US and placental MRI between August 2006 and January 2012. Correlation with clinical history and pathologic findings was performed. RESULTS: US and MRI had similar sensitivity, specificity and positive and negative predictive values for placenta accreta. The best predictors of invasion by US were loss of the myometrial mantle, increased intraplacental vascularity and loss of the bladder wall echogenicity. The best predictors of invasion by MRI were loss of retroplacental myometrial mantle, a heterogeneous placenta, and intraplacental hemorrhage. Body mass index (BMI) did not affect the ability to make a diagnosis by either US or MRI. MRI proved effective in better evaluation of a posterior placenta with suspicion of placenta accreta. There was modality disagreement in 11 of 45 cases and MRI was correct in 9 of these 11 cases, all true negative (TN) cases. CONCLUSIONS: MRI should be considered in any case with posterior placenta previa and suspicion of accreta, in any case with clinical suspicion for accreta and discordant US findings, and in any case in which percreta is suspected.

Interstitial twin pregnancy: A unique case presentation.

Early recognition and timely treatment of an interstitial pregnancy is imperative to avoid the high morbidity and mortality of this type of ectopic pregnancy. We report a case of twin interstitial pregnancy that was initially missed on initial sonogram and was subsequently recognized at our institution by transvaginal sonography. The patient underwent open laparoscopic surgery with cornual wedge resection but suffered infundibulopelvic ligament hemorrhage and subsequently required ipsilateral salpingo-oophorectomy. She did well and was discharged home a day later.

How much free fluid can a pregnant patient have? Assessment of pelvic free fluid in pregnant patients without antecedent trauma.

BACKGROUND: The amount of free fluid that can normally be present in a pregnant patient is unknown. Evaluation of pelvic free fluid in a population of pregnant patients without early history of trauma would help determine what amount of free fluid should raise suspicion of intra-abdominal injury in those who have suffered trauma. METHODS: Patients presenting for routine obstetric ultrasound without an early history of trauma were offered participation in the study. Routine imaging of the cul de sac and ovaries was used for assessment of presence or absence of free fluid, with accompanying digitally recorded images. Depth of the fluid pocket was measured in millimeters. RESULTS: Six of 89 patients successfully scanned were found to have free fluid in to the cul de sac for an occurrence of 6.7%. Four patients had free fluid present during the first trimester with subsequent resolution by the late first trimester or early second trimester. Two of these patients had an identifiable cause for free fluid, one with right ovarian hyperstimulation and the second with idiopathic theca lutein cysts. Two patients had isolated free fluid appearing in the third trimester. CONCLUSIONS: These results suggest that the presence of pelvic free fluid in pregnant patients without antecedent trauma is very low. After blunt abdominal trauma, the presence of free fluid in the pelvis of a pregnant patient may not be physiologic, especially if there is >2 mm to 4 mm, and there is no history of ovarian hyperstimulation syndrome or other known associations.

Fetal radiation dose during gestation estimated on an anthropomorphic phantom for three generations of CT scanners.

OBJECTIVE: The purpose of this study is to determine fetal dose during four different stages of pregnancy for both pulmonary CT angiogram and abdominal and pelvic CT examination on 4-, 16-, and 64-MDCT scanners measured in an anthropomorphic phantom simulating a pregnant patient. MATERIALS AND METHODS: Pulmonary angiograms and abdominal and pelvic studies were performed on a phantom on 4-, 16-, and 64-MDCT scanners. Fetal positioning and mean fetal depth were determined using data from ultrasound examinations of a large cohort of patients. Scans were performed for early pregnancy and for 10, 18, and 36 weeks. Gestational age, fetal dose, and entrance skin exposure were measured. RESULTS: When constant parameters were used for pulmonary CT angiograms, the fetal radiation dose was not significantly associated with gestational age. For abdominal examinations, the 64-MDCT scanner imparted a 20% higher dose during the third trimester than did the other scanners. When scanning parameters were kept constant between machines, gestational age and fetal dose were not significantly different. However, when the manufacturer-recommended protocols for pregnant patients were used, the dose was significantly higher in the third trimester on the 64-MDCT scanner. CONCLUSION: The 64-MDCT scanner is the most dose-efficient machine when the fetus is outside the direct scan volume, as in the case of pulmonary angiograms. For abdominal examinations, the 64-MDCT scanner imparted the highest fetal dose. This finding is attributable to the increased tube current used to penetrate the larger amount of soft tissue in late pregnancy. Abdominal shielding may reduce fetal dose without affecting diagnostic ability.

Fetal magnetic resonance imaging: a review.

PURPOSE OF REVIEW: To describe advances in magnetic resonance technology and the current indications and advantages of magnetic resonance imaging that have led to increased utilization in fetal medicine. RECENT FINDINGS: The article covers the most common uses of magnetic resonance imaging in fetal medicine. The advantages of magnetic resonance imaging for the diagnosis of fetal malformations are described, in particular the advantages of magnetic resonance imaging in central nervous system malformations not optimally diagnosed by ultrasound are described. These cases include malformations of migration, malformations of development, such as agenesis of the corpus callosum, and destructive lesions. Noncentral nervous system lesions include chest abnormalities, abdominal wall defects, gastrointestinal and genitourinary abnormalities and fetal neoplasms. Abnormalities of placentation and other maternal factors affecting pregnancy are shown. SUMMARY: Recent studies have shown that magnetic resonance imaging can add significantly to the prenatal diagnosis and management of congenital abnormalities. In addition, placental abnormalities have been diagnosed with greater accuracy.

The value of specific MRI features in the evaluation of suspected placental invasion.

OBJECTIVE: The objective of this study was to determine imaging features that may help predict the presence of placenta accreta, placenta increta or placenta percreta on prenatal MRI scanning. SUBJECTS AND METHODS: A retrospective review of the prenatal MR scans of 10 patients with a diagnosis of placenta accreta, placenta increta or placenta percreta made by pathologic and clinical reports and of 10 patients without placental invasion was performed. Two expert MRI readers were blinded to the patients' true diagnosis and were asked to score a total of 17 MRI features of the placenta and adjacent structures. The interrater reliability was assessed using kappa statistics. The features with a moderate kappa statistic or better (kappa > .40) were then compared with the true diagnosis for each observer. RESULTS: Seven of the scored features had an interobserver reliability of kappa > .40: placenta previa (kappa = .83); abnormal uterine bulging (kappa = .48); intraplacental hemorrhage (kappa = .51); heterogeneity of signal intensity on T2-weighted (T2W) imaging (kappa = .61); the presence of dark intraplacental bands on T2W imaging (kappa = .53); increased placental thickness (kappa = .69); and visualization of the myometrium beneath the placenta on T2W imaging (kappa = .44). Using Fisher's two-sided exact test, there was a statistically significant difference between the proportion of patients with placental invasion and those without placental invasion for three of the features: abnormal uterine bulging (Rater 1, P = .005; Rater 2, P = .011); heterogeneity of T2W imaging signal intensity (Rater 1, P = .006; Rater 2, P = .010); and presence of dark intraplacental bands on T2W imaging (Rater 1, P = .003; Rater 2, P = .033). CONCLUSIONS: MRI can be a useful adjunct to ultrasound in diagnosing placenta accreta prenatally. Three features that are seen on MRI in patients with placental invasion appear to be useful for diagnosis: uterine bulging; heterogeneous signal intensity within the placenta; and the presence of dark intraplacental bands on T2W imaging.

Multicystic encephalomalacia after first-trimester intrauterine fetal death in monochorionic twins.

Multicystic encephalomalacia occurs in approximately 20% of surviving cotwins after second- and third-trimester intrauterine fetal death of one twin in monochorionic pregnancies. We report a case of multicystic encephalomalacia after the demise of a cotwin in the first trimester diagnosed by magnetic resonance imaging and confirmed pathologically.

Prenatal diagnosis for detection of aneuploidy: the options.

The value of all noninvasive prenatal tests must be viewed with the perspective of the consequences of invasive testing. Regarding second trimester noninvasive testing, biochemical screening is more accurate in establishing risk than maternal age alone. One or more major ultrasound abnormalities, nuchal thickening, or a shortened humerus should raise concern for Down syndrome regardless of the patient's a priori risk based on age or biochemical markers. Isolated minor ultrasound markers should not be used in calculating risk in low-risk patients regarding Down syndrome unless the biochemical profile already places the patient at risk or in a borderline risk zone. If the ultrasound finding is hyperechoic bowel, problems other than aneuploidy may be the cause, including cystic fibrosis, infection, or hemorrhage, and these problems must be considered if hyperechoic bowel is an isolated finding. Improved risk adjustment seems to be applicable to a priori high-risk patients with completely normal sonograms. Genetic sonograms with specific risk adjustment schemata may be used to adjust a priori risk (either maternal age or biochemical screening results) at centers in which this has proven to be accurate, but whether this is statistically sound remains to be determined. The goal of second trimester ultrasound screening is to identify at-risk fetuses better and offer invasive testing to a more select group of patients. As the value of first trimester screening becomes more evident and practical, and if the risk of chorionic villus sampling becomes an acceptable norm, the patient population that reaches the second trimester of pregnancy will be select. Therefore, we can anticipate that second trimester screening and invasive testing may be needed only in a minority of cases, and the practice standards of prenatal testing and sonography (including minor ultrasound markers) will change entirely.