[Tetragametic chimerism: Case report]. / Chimérisme tétragamétique : à propos d'un cas.

We report the third case of spontaneous monochorionic dizygous pregnancy, discovered on foetal sex discordance. Blood group testing on the female twin revealed a hematopoietic chimera. The mechanism of monochorionic dizygous formation could be the fusion of two independent zygotes at a late morula stage. A single placental mass with vascular anastomosis then develops. Stem cells exchanged during early foetal life can thus lead to chimeras, in similar conditions to stem cell transfusion in adults. Immaturity of the foetal immune system allows cell graft in the other twin's marrow. Assisted reproductive procedures are believed to promote such pregnancies.

Semi-automated adjusted measurement of nuchal translucency: feasibility and reproducibility.

OBJECTIVE: The variability of nuchal translucency thickness (NT) measurements in the first trimester appears to be associated in part with caliper placement. Methods for obtaining semi-automated adjusted measurements (SAAMs) can provide several NT values (maximum, minimum, mean and median) automatically within a manually set frame in the zone of interest. This study sought to assess the feasibility and reproducibility of these SAAM-NTs. METHODS: Three readers, two experts and one less experienced, examined archive images of 160 patients and obtained SAAM-NTs from them, on two separate occasions. The intra- and interobserver reproducibility were assessed by calculating the intraclass correlation coefficients (ICCs) for maximum, mean and median SAAM-NTs, and Bland-Altman plots were constructed. RESULTS: SAAM-NTs were technically feasible for all 160 images. The range of ICCs for intraobserver reproducibility was 0.76-0.93 for mean SAAM-NT, 0.76-0.95 for median SAAM-NT and 0.74-0.95 for maximum SAAM-NT. Interobserver ICCs were 0.85, 0.85 and 0.84 for mean SAAM-NT, median SAAM-NT and maximum SAAM-NT, respectively. There were no significant differences for intra- and interobserver reproducibility of median, mean and maximum SAAM-NTs. CONCLUSIONS: SAAM-NT is feasible with a high level of intra- and interobserver reproducibility. This easy-to-use method has the potential to simplify screening during the first trimester. It should be evaluated further and compared with the manual measurement method.

Ultrasonography of the fetal brainstem: a biometric and anatomical, multioperator, cross-sectional study of 913 fetuses of 21-36 weeks of gestation.

OBJECTIVES: To establish the ultrasonographic fetal growth charts of the pons and the vermis/pons ratio on a multioperator basis in low-risk pregnancies and provide a detailed description of the anatomical and ultrasonographic criteria of normal brainstem growth. METHODS: A prospective, multicenter, multioperator, ultrasonographic study was conducted on 913 fetuses aged 21-36 weeks. The anteroposterior diameter of the pons and the greatest vermal height were measured to establish a growth chart, using a mid-sagittal plane with a posterior transfontanellar approach. The LMS semiparametric statistical method was used to construct the growth charts. Three morphological structures were also examined: the pons arch and its echostructure, the bulbo-protuberential sulcus and the primary vermal fissure. RESULTS: The anteroposterior diameter of the pons and the greatest vermal height were measured in 96.7% of cases. The anteroposterior diameter of the pons and vermis increased linearly with gestational age. The vermis/pons ratio was stable during pregnancy. CONCLUSION: We have drawn the growth charts for the pons and vermis during pregnancy and described the normal ultrasound morphology of the brainstem. Knowledge of these morphological and biometric data could facilitate early screening for pontocerebellar hypoplasia.

Brachytelephalangic chondrodysplasia punctata: prenatal diagnosis and postnatal outcome.

We report the prenatal management of a brachytelephalangic chondrodysplasia punctata (CDPX1) case and how postnatal findings confirmed the diagnosis. The mother was initially referred after ultrasound revealed an abnormal fetal mid-face and punctuation of upper femoral epiphyses. Chondrodysplasia punctata (CP) with Binder anomaly was suspected. 3D-HCT revealed brachytelephalangy suggesting CDPX1. At birth, mid-face hypoplasia was marked. Postnatal imaging and genetic analysis confirmed the initial diagnosis. Binder anomaly is probably always associated with CP. The newly revised CP classification facilitates the diagnosis. The main etiologies are metabolic and chromosomal abnormalities, and arylsulfatase E enzyme dysfunction. Thus, screening for arylsulfatase E mutation is mandatory for an accurate diagnosis and can lead to better delineation among CP etiologies associated with a Binder phenotype.

French fetal biometry: reference equations and comparison with other charts.

OBJECTIVES: To construct new reference charts and equations for fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL), using a large sample of fetuses examined at 15-40 weeks in France, and to compare them with previous references. METHODS: The study data were obtained over a continuous 1-year period from a population of pregnant women undergoing ultrasound examination. Excluded were those with a known abnormal karyotype or congenital malformation, multiple pregnancies, and those with no first-trimester dating based on crown-rump length. No fetuses were excluded on the basis of abnormal biometry or birth weight. For each measurement, separate regression models were fitted to estimate both the mean and the SD at each gestational age. RESULTS: Full biometric measurements were obtained for 19 647 fetuses. New charts and reference equations are reported for BPD, HC, AC and FL. Prediction intervals for the new reference charts were similar to those of previous ones, whereas there were some differences in predicted centiles. CONCLUSION: We present new French reference charts and equations for fetal biometry. They can be used easily to compute centiles and Z-scores to control the quality of biometric assessments and to evaluate their performance relative to other references.

[Role of "subtle" ultrasonographic signs during antenatal screening for trisomy 21 during the second trimester of pregnancy: meta-analysis and CPDPN protocol of the Grenoble University Hospital]. / Quelle est la place des signes d'appels échographiques dits "mineurs" dans le dépistage prénatal de la trisomie 21 au 2e trimestre de la grossesse? Méta-analyse de la littérature et protocole du Centre pluridisciplinaire de Dignostic Prénatal (CPDPN) du CHU de Grenoble.

OBJECTIVE: A meta-analysis about subtle ultrasonographic signs in second trimester of pregnancy. MATERIALS AND METHODS: 196 articles dealing with the subject--from 1985 to July 2002--were studied. Data on the 11 reported signs were collected from 92 theoretically and/or statistically valid studies. Then, the studies were selected according to several criteria: isolated characteristic, defined thresholds, calculable sensitivity and specificity. After checking for homogeneity, a likelihood ratio was calculated for some of the signs. RESULTS: This meta-analysis of the second trimester ultrasonographic signs of Down's syndrome enabled us to estimate the likelihood ratio (LHR) of six signs. At 22 weeks'gestation (WG) these signs are: pyelectasis equal to or greater than 5 mm; nuchal fold thickness equal to or greater than 6 mm; persistence of choroid plexus cysts; shortness of the femur and humerus below the tenth percentile; hyperechogenic bowe; and nasal bone length less than 2.5 mm. CONCLUSION: These validated ultrasonographic signs are independent of nuchal translucency thickness at 12 WG and of maternal serum biochemistry. This allows to calculate a combinate risk for nuchal translucency, maternal serum biochemistry and second trimester ultrasonographic signs when they are validated.

A submicroscopic unbalanced subtelomeric translocation t(2p;10q) identified by fluorescence in situ hybridization: fetus with increased nuchal translucency and normal standard karyotype with later growth and developmental delay, rhombencephalosynapsis (RES).

Reaching an accurate diagnosis in children with mental retardation associated or not with dysmorphic signs is important to make precise diagnosis of a syndrome and for genetic counseling. A female case with severe growth and development delay, dysmorphic features and feeding disorder is presented. Antenataly, the fetus was observed to have increased nuchal translucency and a slight hypoplastic cerebellum. A standard karyotype was normal. RES and a submicroscopic unbalanced subtelomeric translocation t(2p; 10q) were demonstrated after birth. We show that within the framework of a collaborative approach, a concerted research of submicroscopic subtelomeric rearrangements should be performed in case of mental retardation associated with facial dysmorphic features, and when other etiologies or non-genetic factors (iatrogenic, toxic, infectious, metabolic...) have been ruled out.

[Combined use of nuchal translucency, gestational age and maternal age for evaluation of the risk of trisomy 21]. / Utilisation conjointe de la clarté nucale, de l'âge gestationnel et de l'âge maternel pour l'estimation du risque de trisomie 21.

PURPOSE: Despite the definition of new screening policies for fetal trisomies, based on nuchal translucency thickness (NT) or maternal serum, the prevalence of trisomy 21 remains high. We propose a strategy based on a combination of maternal age, gestational age and NT, measured at the first trimester ultrasound examination, for the assessment of risk. METHODS: We present, in this paper, a characterisation of the physiological increase of fetal NT between the 10th and the 14th week of gestation, in a preliminary study of 266 echographic examinations. Next we propose a calculation of the simultaneous risk of trisomy 21 based on marginal risks for maternal age and increased NT values available in the literature. RESULTS AND CONCLUSION: We propose to define a high-risk group associated to the NT marker by using a cut-off risk of 1/250 for the simultaneous risk. This criteria may, as well, be expressed by a pathological threshold of NT varying with maternal age and gestational age. Without questioning that women aged of 38 years or older are a high-risk group, this approach should allow an improvement of the prenatal screening for trisomy 21.