ACR Appropriateness Criteria® Second and Third Trimester Screening for Fetal Anomaly

The Appropriateness Criteria for the imaging screening of second and third trimester fetuses for anomalies are presented for fetuses that are low risk, high risk, have had soft markers detected on ultrasound, and have had major anomalies detected on ultrasound. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Imaging findings in association with altered maternal alpha-fetoprotein levels during pregnancy

Maternal serum alpha-fetoprotein is a valuable laboratory test used in pregnant women as an indicator to detect certain clinical abnormalities. These can be grouped into four main categories: fetal factors, pregnancy complications, placental abnormalities, and maternal factors. Imaging is an invaluable tool to investigate the various etiologies leading to altered maternal serum alpha-fetoprotein. By reading this article, the radiologist, sonologist, or other health care practitioner should be able to define the probable pathology leading to the laboratory detected abnormal maternal serum levels, thus helping the clinician to appropriately manage the pregnancy and counsel the patient.

Evidence for the Oocyte Mosaicism Selection model on the origin of Patau syndrome (trisomy 13)

INTRODUCTION

In 2008, Hultén et al hypothesized that maternal ovarian trisomy 21 mosaicism might be the primary causative factor for fetal Down syndrome. We hypothesize that this theory can be extended to trisomy 13.

MATERIAL AND METHODS

We collected fetal ovarian tissue from seven female fetuses between 16 and 23 gestational weeks, following the termination of the pregnancy for non-genetic reasons. All procedures were performed with informed consent and ethical approval from the local ethics committee. We used touch preparation techniques from fetal ovarian tissues and an anti-stromal antigen 3 antibody against the meiosis-specific stromal antigen 3 protein to differentiate between germ cells, ovarian stromal cells and the cells entering their first meiotic prophase. We used fluorescence in situ hybridization analysis to determine chromosome 13 numbers in each cell.

RESULTS

We were able to detect a proportion of trisomy 13 cells in all cases. The average incidence of trisomy 13 cells was 2.04% in stromal antigen 3-positive and 0.91% in the stromal antigen 3-negative cells. The number of the trisomic cells increased significantly with gestational age (for stromal antigen 3-positive cells r = 0.93, P = 0.0038, for stromal antigen 3-negative cells r = 0.85, P = 0.0071).

CONCLUSIONS

This study indicates that besides trisomy 21, the Oocyte Mosaicism Selection model could be extended to trisomy 13 as well. The crucial factor for trisomy 13 seems to be the pre-meiotic/mitotic trisomy 13 mosaicism, leading to a so-called secondary meiotic nondisjunction of those oocytes having three copies of chromosome 13.

Turner syndrome: New insights from prenatal genomics and transcriptomics

In some parts of the world, prenatal screening using analysis of circulating cell-free (cf) DNA in the plasma of pregnant women has become part of routine prenatal care with limited professional guidelines and without significant input from the Turner syndrome community. In contrast to the very high positive predictive values (PPVs) achieved with cfDNA analysis for trisomy 21 (91% for high-risk and 82% for low-risk cases), the PPVs for monosomy X are much lower (~26%). This is because the maternal plasma sample contains both maternal cfDNA and placental DNA, which is a proxy for the fetal genome. Underlying biological mechanisms for false positive monosomy X screening results include confined placental mosaicism, co-twin demise, and maternal mosaicism. Somatic loss of a single X chromosome in the mother is a natural phenomenon that occurs with aging; this could explain many of the false positive cfDNA results. There is also increased awareness of women who have constitutional mosaicism for 45, X who are fertile. It is important to recognize that a positive cfDNA screen for 45, X does not mean that the fetus has Turner syndrome. A follow-up diagnostic test, either amniocentesis or neonatal karyotype/chromosome microarray, is recommended. Research studies on cell-free mRNA in second trimester amniotic fluid, which is almost exclusively fetal, demonstrate consistent dysregulation of genes involved in the hematologic, immune, and neurologic systems. This suggests that some of the pathophysiology of Turner syndrome occurs early in fetal life and presents novel opportunities for consideration of antenatal treatments.

Triploidy: Variation of Phenotype

OBJECTIVES

Triploidy (69, XXX; 69, XXY; 69, XYY) accounts for 1% of conceptions, but the affected fetus often does not survive past the first trimester. Fetal development in triploidy is rare. A consecutive series was used to describe the fetal and placental phenotypes and compare them with previous publications.

METHODS

Fifty-four triploid fetuses were identified in the Active Malformations Surveillance Program between 1972 and 2012 at Brigham and Women's Hospital in Boston. The phenotype was described from prenatal imaging and autopsy findings.

RESULTS

The diagnosis was confirmed by chromosome analysis in 53 of the 54 fetuses. Twenty-seven (50%) of the affected fetuses were identified during pregnancy. The abnormalities identified by prenatal ultrasound included renal malformations, heart defects, hydrocephalus, holoprosencephaly, and myelomeningocele. At autopsy, syndactyly, usually between fingers 3 and 4, was identified in 37 (69%) of the fetuses. Thirteen (24%) of the infants had the histologic features of a partial hydatidiform mole in the placenta.

CONCLUSIONS

The presence of major malformations and growth restriction during pregnancy makes triploidy a potential diagnosis. There are no obligate clinical features in triploidy. Syndactyly, especially 3-4 syndactyly of the hands, is a distinctive feature. Cystic changes in the placenta can be seen by ultrasound during pregnancy. There was no difference in the phenotype between triploid infants associated with partial moles and those with nonmolar placentas.