Conjoined twins: prenatal diagnosis and assessment of associated malformations

Article Abstract:

Conjoined twins (joined together; commonly known as Siamese twins) do not often occur. Most conjoined twins are female and many die before birth. Diagnosis of this condition prior to birth has been greatly facilitated by new technologies. The imaging techniques of ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MR) can detect and help evaluate this condition. Early detection of conjoined twins helps in making decisions about terminating pregnancy, type of delivery, and care and treatment of problems associated with this defect. The problems vary greatly, depending upon the location and extent of the fusion of the fetuses. This study reviewed imaging information on 14 cases of conjoined twins to develop useful guidelines for future cases. Imaging examinations should be considered when a twin pregnancy is found to have a single placenta and the amniotic membrane is not visibly separated; these are indications of conjoined twins. US indicators of conjoined twins include inseparable fetal bodies, inseparable skin contours, and no relative changes in fetal position. The sonograms must be examined closely since false-positive diagnosis (identification of fusion in a normal twin pregnancy) may occur. US findings revealed that most conjoined twins were fused such that they faced each other, and many shared the same heart as well as other organs. This information is important in determining whether or not to separate the twins at birth, and whether or not to terminate the pregnancy. Imaging is important in determining type of delivery, because vaginal delivery can adversely affect both the mother and the twins, depending on the size of the twins and how they are connected. The prognosis for conjoined twins is poor, but accurate diagnosis and assessment are necessary in deciding what steps to take to ensure the safety of the mother and, if possible, the survival of one or both of the twins. (Consumer Summary produced by Reliance Medical Information, Inc.)

Methods, Diagnosis, CT imaging, CAT scans, Magnetic resonance imaging, Conjoined twins, Prenatal diagnosis

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Earlier diagnosis of fetal anomalies: quo vadis?

Article Abstract:

In the December 1991 issue of Radiology, Ragavendra and colleagues describe their experience with an imaging technique that could accurately detect embryonic malformations in early pregnancy. The technique, endoluminal transcervical ultrasonography (ELCAT sonography), involves passing a catheter into the uterus during early pregnancy and then performing ultrasound imaging. The catheterization used in this procedure is similar to that used for chorionic villus sampling (CVS), which suggests that ELCAT is probably very safe. However, safety studies should still be performed. One justification given for the development of this technique is that the current procedure for evaluating the early embryo, transvaginal sonography (TVS), is inadequate. Such a statement does a great disservice to TVS. Although ELCAT has the potential to more accurately depict embryonic anatomy, TVS is advantageous in a number of other ways. TVS is certainly more convenient and less invasive than ELCAT. ELCAT provides a limited view and is more likely to be used for evaluation of specific malformations rather than for general evaluation. Many anomalies can not be recognized during the early embryonic stage. From a scientific viewpoint, this technology is an advancement, but from a clinical viewpoint it may be of little use. To be fair to ELCAT, earlier diagnosis in specific types of cases is always welcome, but it is not yet time to replace TVS with ELCAT. (Consumer Summary produced by Reliance Medical Information, Inc.)

Editorial, Innovations, Evaluation, Human embryo, Prenatal ultrasonography, Ultrasonics in obstetrics

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Accuracy of right ventricular output estimated by Doppler echocardiography in the sheep fetus

Article Abstract:

Doppler echocardiography of right ventricular output in fetal sheep appears to accurately estimate fetal heart output. Doppler echocardiography in the human fetus has been limited, and its accuracy in measuring heart output and stroke volume remains unknown. Right ventricular output was measured in six sheep fetuses using Doppler echocardiography, a transit-time ultrasonic flowmeter and a microsphere technique. Of 72 flow measurements, 34 were obtained by the transabdominal approach and 38 were obtained by the transuterine approach. The transabdominal approach estimated fetal heart output well, but the correlation between fetal heart output and Doppler echocardiography was significantly better when the transuterine approach was used. The correlation between the transit-time flowmeter and the microsphere measurement was extremely good, indicating the accuracy of Doppler echocardiography in measuring right ventricular output.

Usage, Measurement, Cardiac output, Doppler echocardiography

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