GENETIC SONOGRAM: COMPONENTS AND ROLE IN THE ERA OF PRENATAL SCREENING

The likelihood of detecting abnormal karyotypes in fetuses with a single major anomaly or "soft" marker on ultrasonographic scanning

OBJECTIVE

Fetuses with abnormal karyotypes often exhibit distinctive ultrasonographic markers, including major anomalies and "soft" markers, indicating potential chromosomal issues. A crucial consideration arises when a single fetal anomaly is detected, raising the question of whether karyotyping is warranted, given the associated procedural risks. Our objective was to establish correlations between single fetal anomalies identified through ultrasound and chromosomal abnormalities.

METHODS

A cross-sectional study analyzed the karyotype of 1493 fetuses and detected a single ultrasonographic anomaly over a 16-year period. Karyotyping was performed using the standard karyotype technique. Moreover, data regarding the type of anomaly detected ultrasonographically, karyotype results, and outcomes following interventions were collected. Among other methods, the use of positive likelihood ratios (LR+) was used to evaluate the diagnostic accuracy of ultrasound compared to karyotyping.

RESULTS

In total, an aberrant karyotype was identified in 99 fetuses (6.6%). This was most commonly observed in cases involving a "soft" marker, occurring in 27 out of 218 fetuses (12.4%). The most frequently detected aberrant karyotype resulted from aneuploidies (80.6% of cases), notably trisomy 21 (50.5%). "Soft" markers predicted chromosomal issues (LR+ = 1.9; OR = 2.4), and isolated polyhydramnios (LR+ = 1.54; OR = 1.6) showed significance in predicting fetal chromosomal aberrations.

CONCLUSION

When assessing the necessity for karyotyping in fetuses with single major anomalies or "soft" markers, it is crucial to consider individual risks for chromosomopathies, including the LR+ of the detected marker. In cases where fetuses exhibit isolated anomalies with a normal karyotype, additional diagnostic measures, such as molecular cytogenetic and molecular genetics techniques, may become necessary.

Non-Invasive Prenatal Testing in Germany

In the short 10 years following the introduction of non-invasive prenatal testing (NIPT), it has been adapted in many countries around the world as a standard screening test. In this review, this development was analyzed with a special focus on Germany. As a result, it can be stated that all known advantages of NIPT apart from "compensating for having no access to centers offering invasive diagnostics" are valid for Germany. In addition, following a review of the international literature, all documented issues with NIPT are also observed in Germany. However, the German Gene Diagnostics Act (GenDG) addresses a number of these issues, for example, the regulations by GenDG hamper induced abortions, based exclusively on an abnormal NIPT result. At the same time, GenDG has created new problems, as a possible collusion between the "right not to know with regard to parts of the examination result" may occur, or that the sex of the fetus must not be reported to the pregnant woman before the 12th week of gestation. Main conclusions drawn are that appropriate training and the continuing education of the physicians providing NIPT-related counseling are needed, as well as the provision of balanced and comprehensive information for the pregnant woman or the couple that is imperative.

Ethical issues in fetal therapy

The introduction of routine fetal ultrasound and the technical improvements in ultrasound equipment have greatly increased our ability to diagnose fetal anomalies. As a consequence, congenital anomalies are diagnosed today earlier and in a greater number of patients than ever before. The development of fetal intervention and fetal surgery techniques, improved anesthesia methodology, and sophisticated perinatal care at the limits of viability, have now made prenatal management of some birth defects or fetal malformations a reality. The increasing number of indications for fetal therapy and the apparent desire of parents to seek out these procedures have raised concern regarding the ethical issues related to the therapy. While fetal therapy may have a huge impact on the prenatal management of some congenital birth defects and/or fetal malformations, because of the invasive nature of these procedures, the lack of sufficient data regarding long-term outcomes, and the medical/ethical uncertainties associated with some of these interventions there is cause for concern. This chapter aims to highlight some of the most important ethical considerations pertaining to fetal therapy, and to provide a conceptual ethical framework for a decision-making process to help in the choice of management options.