IRM fœtale : indications, limites et dangers

[Fetal MRI practices in a university prenatal center]

OBJECTIVES

Fetal MRI is a third intention examination to prenatal diagnosis. If its diagnostic value is well known in many pathologies, its place in the management of pregnancies remains unclear.

METHODS

We collected retrospectively demographical, radiological (fetal MRI indications, fetal anatomical region and diagnostic information provided by fetal MRI) and obstetrical data of pregnant patients in university prenatal center during a 5 years' period.

RESULTS

Among 2439 patients of the prenatal center, 196 (8%) patients with fetal MRI were included. The main anatomical regions studied were the brain (n=132, 67%), the thorax (n=31, 16%) and the abdomen (n=25, 13%). No cardiac fetal MRI was performed. Ninety-five percent of fetal MRI was consecutively of an ultrasound sign. Fetal brain MRI was abnormal in 65% of cases, the thoracic and abdominopelvic MRI in 81.5%. The ultrasound diagnosis was unchanged in 42%, completed in 50% and redirected in 8% of cases. A termination of pregnancy was deemed admissible in 31% of patients with MRI versus 21% in patients without MRI (P=0.001).

CONCLUSION

Fetal MRI requires selective indications and provides additional diagnostic information with important implications for the future of the pregnancy, particularly in case of severe and incurable pathologies. Our results could be useful as a reference basis for the comparison with others prenatal center practices.

[Segmental approach to congenital heart diseases: Principles and applications to prenatal imaging]

This pictorial essay will initially present the origin, definitions, objectives and main principles of the segmental approach to congenital heart diseases. Then, through ultrasound scans iconography we will consider its practical applications to prenatal screening. Eventually, through both ultrasound and MRI cases, we will discuss its potential use in fetal diagnostic evaluation.

[Epignathus teratoma: diagnostic and neonatal management; a case report]

Epignathus teratoma is a rare tumor whose prognosis essentially depends on its resectability and on neonatal care. When it is undiagnosed prenatally, mortality is close to 100 % at birth, because of obstruction of the upper airways. We present a case of epignathus teratoma detected during obstetrical ultrasound screening. Diagnosis enabled planning for a safe delivery in a suitable multidisciplinary unit and use of the EXIT procedure.

Quality initiatives: guidelines for use of medical imaging during pregnancy and lactation

The use of computed tomography (CT) and magnetic resonance (MR) imaging has increased tremendously in the past 2 decades. Hence, pregnant and breast-feeding women, although generally healthier than the population at large, are also more likely to require contrast material-enhanced imaging. When a contrast-enhanced CT or MR imaging study is being considered for a pregnant or lactating patient, the potential risks to the fetus related to exposure to radiation, high magnetic fields, or contrast agents must be considered and weighed carefully against the risks of potential misdiagnosis due to withholding contrast agents and imaging studies. Fetal radiation doses up to 1 mGy are considered acceptable; with larger doses, the risk of carcinogenesis approximately doubles, although it remains low in absolute terms. No damage to a developing human fetus caused by MR imaging exposure has been documented. However, caution is advised, and risks and benefits must always be considered before evaluating a pregnant patient with MR imaging. The use of iodinated contrast agents is generally safe during pregnancy; nevertheless, these agents should be used with caution due to the risk of fetal hypothyroidism and should be administered only when the clinical situation clearly requires doing so. The use of gadolinium-based contrast agents during pregnancy remains controversial due to lack of human clinical data and potential toxicity. Use of all contrast agents is considered safe during lactation. It is hoped that this knowledge will help radiologists develop a consensus with their clinical colleagues regarding case management of pregnant and lactating patients.

[Unusual fetal teratoma presenting as a posterior mediastinal cyst]

Mediastinal cysts are uncommon prenatal findings. As isolated and non-compressing entities, they don't compromise the course of gestation. Massive lesions can compress vital structures, resulting in fetal demise. Thus, close follow-up with sonographic monitoring is recommended until birth. Non-hydroptic fetuses can be managed expectantly. Definitive etiology is known after surgical resection only. We present the first case of posterior mediastinal teratoma associated with severe vertebral abnormalities. After CT scan and fetal MRI, medical termination of pregnancy was decided. Histological examination revealed an immature teratoma. With this unique case report, we discuss the optimal prenatal management of mediastinal cysts.

[Asphyxiating thoracic dysplasia (Jeune syndrome): about two cases]

Asphyxiating thoracic dysplasia (Jeune syndrome) is an osteochondrodysplasia with autosomal recessive inheritance, characterised by a nanism with rhizomelic predominance, associated with a narrow thorax. It induces an alteration of the respiratory function that conditions the prognosis, which is worsened in case of associated visceral lesions (probably related to mutations of genes implicated in ciliary development, as recently described). We report the observation of two severe cases of Jeune syndrome to emphasize the advancement of imaging, especially echography, and molecular biology in establishing prenatal diagnosis as well as prognosis of this syndrome.