[Magnetic resonance imaging applications in obstetrics]

PURPOSE

To review the main indications and results of magnetic resonance imaging in the pregnant women.

MATERIAL AND METHOD

We reviewed MRI practice during the pregnancy based on our own experience in a prenatal diagnostic center and data in the literature. Rapid improvement in MRI technology has allowed more extensive use, giving a good contrast-to-noise ratio and multiplanar imaging.

RESULTS

Although ultrasound provides primary screening information, final diagnosis may require further investigations. MRI, to be performed in the second and third trimester, is the non-invasive second line tool of choice in this context. The most widespread indications are for brain disease: search for a cause of ventriculomegaly or biometric abnormality, confirmation of a malformative or acquired lesion. Progressively, indications were widened to head and neck, thorax, abdomen and pelvis areas. Moreover, systematic indications include previous fetal pathology or the pregnancy context. Other MRI indications have been suggested: placental malposition, pelvimetry and maternal genito-urinary tract.

CONCLUSION

MRI is becoming the natural and necessary second line imaging technique, with increasing indications. It must be kept in mind however that all pathological conditions cannot be depicted by these morphological studies.

[Trisomy 18: ultrasound aspects. Report of 40 cases]

OBJECTIVE

We describe the different ultrasound findings suggestive of trisomy 18.

PATIENTS AND METHODS

We conducted a retrospective study in 40 cases of trisomy 18 diagnosed in the department of obstetrics at the Lille University Hospital between 1988 and 1998.

RESULTS

Eighty percent of the women in this series were multiparous. Mean maternal age at discovery of the trisomy as 33.2 years and the mean gestational age was 20.4 weeks. Fifty-five percent of the cases were discovered during the second trimester of pregnancy, 22.5% during the third trimester and 22.5% during the first trimester. One ultrasound abnormality, at least, was detected in 36/40 cases (90%) a percentage that reached 96.8% taking into consideration the ultrasound examinations performed during the second and third trimesters (30/31 cases). The most frequently detected ultrasound abnormalities were: intra uterine growth retardation (IUGR: 50%), poly-hydramnios (42.5%), limb abnormalities (42.5%), cardiac defects (30%), facial abnormalities (37.5%), meningomyelocele (32.5%), digestive abnormalities (32.5%), urinary tract abnormalities (27.5%), lymphangiectasia and cystic hygroma (15%), and single umbilical artery (12.5%). Medical termination of pregnancy (TOP) was performed in 28 cases. There was one spontaneous miscarriage at 8 weeks and one in utero death (IUD) at 39 weeks in a patient who desired to continue her pregnancy. In 6 cases, the issue of the pregnancy was unknown because the patients were lost to follow-up. In 4 cases (10%), pregnancy was continued to delivery of live babies that only survived a few minutes to 7 days.

CONCLUSION

The ultrasound signs suggestive of trisomy 18 change according to the term of pregnancy. At the first trimester, most of the signs are nonspecific, such as cystic hydroma or lymphangiectasia, and do not suggest the need for a karyotype. At the end of the second trimester, an association of various signs that alone would not be highly suspect suggest the need for further exploration in search of other signs: early IUGR, associated or not with poly-hydramnios, limb abnormalities, cardiac defects, omphalocele, diaphragmatic hernia, meningomyelocele, enlarged cisterna magna, choroid plexus cysts, single umbilical artery, facial dysmorphism, facial cleft, hydronephrosis.

Echographic signs of trisomy 21 in the second trimester of pregnancy: actual value after analysis of the literature

OBJECTIVE

To evaluate the interest and to compare the major echographic signs of Down syndrome in the second trimester of pregnancy.

METHODS

A bibliographic research has been performed for most of the echographic signs known and studied until now. For each study and in average for each sign, we have computed its sensitivity, its specificity, its positive and negative predictive values using the results of the different authors. Then, we have compared the benefits/risk ratio for each of these signs: the number of Down syndrome cases detected versus healthy fetus lost due to amniocentesis complications.

RESULTS

The different signs can be ranked according to their benefits/risk ratio from top to bottom as follows: nuchal skinfold thickness, wide space between first and second toe, pyelectasis, large iliac angle, short humerus, short femur, hypoplasia of the middle phalanx of the fifth digit.

CONCLUSION

These results suggest that second trimester echographic signs of Down syndrome must be evaluated as a function of the Down syndrome risk in the population under study. The presence of these signs does not always justify an amniocentesis; it should lead to a re-evaluation of the individual risk of a Down syndrome (a chart is given to guide this re-evaluation).

[Nuchal translucency: screening for chromosomal abnormalities and congenital malformations. Multicenter study]

OBJECTIVE

To value the rate of chromosomal abnormalities and evolution of children who had a prenatal diagnosis of fetal nuchal translucency in the first trimester.

MATERIAL AND METHODS

Multicenter prospective study conducted in 4,582 patients who had a first ultrasonography between 10 and 14 weeks' gestation (abdominal and/or transvaginal sonography). The measurement of fetal nuchal translucency was performed by mid-sagittal section and when it was higher than 2.5 mm a fetal karyotype was made.

RESULTS

Three hundred and fifty eight nuchal translucencies (> 2.5 mm) were diagnosed and 334 karyotypes were done. We found 25 chromosomal anomalies (7.4%): 14 trisomies 21; 7 trisomies 18; 2 trisomies 13; one triploidy and one trisomy X. The postnatal examination of children detected three congenital malformations (0.9%): one facial dysmorphia, one complex abnormal heart anatomy and one renal agenesia.

CONCLUSION

Nuchal translucency (> 2.5 mm) is therefore a sonography sign associated with 7.4% of chromosomal anomalies. The distribution by size and mother ages is low. It should need superior larger-scale studies are needed for representative data. But this study shows that if fetal karyotype is normal, the incidence of congenital malformations seems to be the same by comparison with the general population.

[Ultrasonographic signs of chromosome aberrations]

We reviewed the literature on ultrasonographic criteria allowing prenatal diagnosis of chromosome aberrations, especially the most frequent: trisomy. Signs vary depending on the term of the ultrasound examination (first trimester ultrasound is often performed to early and several signs are observed in the second trimester). During the first trimester, the main criteria is the diagnosis of nuchal clearness 3 mm. The distance can only be measured with an appropriate sagittal CRL section by an experienced operator. The ideal term of this morphology ultrasound is 10 weeks gestation. During the second trimester, there are many suggestive criteria including non-specific signs: anomalous quantity of amniotic fluid, short femur, nuchal thickness 6 mm, isolated anomaly of the umbilical velocimetry, pyelectasy and fetal malformations (mainly cerebral or abdominal, including ophalocele and diaphragmatic hernia, anomalies, abnormal heart anatomy, cystic hygroma, facial anomalies and malformations of the members, often abnormal flexion of the hands).

[Choroid plexus cysts and risks of chromosome anomalies. Review of the literature and proposed management]

OBJECTIVE

We propose to specify the different criteria of estimation and management in presence of a ultrasound discovery of a choroid plexus cyst.

METHOD

A detailed review of the literature about this subject allowed to better apprehend the different attitudes taken up by the authors.

RESULTS

Fetal choroid plexus cysts (CPC) are potentially useful markers for trisomy 18 in as much as they are present in about 50% of affected fetuses and they are easily seen in the standard biparietal diameter view which is obtained for all routine ultrasound scans. However, advice is contradictory as to whether karyotyping should be proposed for all fetuses (1-2% of the population) where fetal CPC are diagnosed.

CONCLUSION

The review of the literature show that the majority of the authors advocate amniocentesis when the CPC is associated with another ultrasound abnormality. Isolated, it imposes regular and meticulous morphologic ultrasound supervision to search for another possible associated ultrasound abnormality, if necessary, in a prenatal diagnosis center.

Prenatal diagnosis of metatropic dwarfism

We present a case of prenatal diagnosis of severe metatropic dysplasia at 20 weeks' gestation. The characteristic prenatal features of this rare autosomal recessive chondrodysplasia appear to be significant dwarfism with an enlarged head and a narrow thorax associated with enlargement of the hands and feet, and the radiographic 'dumb-bell' appearance of the long bones.

[Obstetric outcome of the malformed uterus. Study of 155 pregnancies]

Gynecological and obstetrical pathologies are considered in 155 pregnancies involving uterine deformity. Evaluation of their relative importance shows that maintenance of pregnancy is more important than pregnancy per se. Certain rules are proposed for treatment and obstetrical management of such pregnancies.

[Non-immunologic hydrops fetalis and congenital chylothorax]

A child was born at the 37th week of pregnancy with hydrops fetalis. Hydramnios and hydrothorax had been proven by fetal ultrasonography. No fetal or maternal etiology was found. At age 4 days, at the beginning of enteral nutrition, the pleural effusion became characteristic of chylothorax. Recovery occurred after 2 weeks of parenteral nutrition. Chylothorax might be an unrecognized etiology of non immune hydrops fetalis. The relationships between both conditions and the interest of prenatal treatment are discussed.