Prenatal diagnosis of a 46,XX male following noninvasive prenatal testing

The Use of Genetics for Reaching a Diagnosis in XY DSD

Reaching a firm diagnosis is vital for the long-term management of a patient with a difference or disorder of sex development (DSD). This is especially the case in XY DSD where the diagnostic yield is particularly low. Molecular genetic technology is playing an increasingly important role in the diagnostic process, and it is highly likely that it will be used more often at an earlier stage in the diagnostic process. In many cases of DSD, the clinical utility of molecular genetics is unequivocally clear, but in many other cases there is a need for careful exploration of the benefit of genetic diagnosis through long-term monitoring of these cases. Furthermore, the incorporation of molecular genetics into the diagnostic process requires a careful appreciation of the strengths and weaknesses of the evolving technology, and the interpretation of the results requires a clear understanding of the wide range of conditions that are associated with DSD.

Fetal sex discordance

Fetal sex discordance is an entity that is becoming more frequent due to the expansion of the cfDNA for prenatal diagnosis. Its incidence can be estimated in 1/1500-2000 pregnancies, a frequency as high as that of some common chromosomopathies. The causes of this phenomenon are multiple and diverse, ranging from laboratory errors to important pathologies such as disorders of sexual differentiation. The management of a case of fetal sex discordance must be structured, starting with the review of the clinical history and the tests performed, and may require the performance of invasive tests to reach a diagnosis. Prevention through adequate pretest counseling and ultrasound confirmation can help to reduce its incidence.

Discordant fetal sex on NIPT and ultrasound

Prenatal diagnosis of sex discordance is a relatively new phenomenon. Prior to cell-free DNA testing, the diagnosis of a disorder of sexual differentiation was serendipitous, either through identification of ambiguous genitalia at the midtrimester morphology ultrasound or discovery of genotype-phenotype discordance in cases where preimplantation genetic diagnosis or invasive prenatal testing had occurred. The widespread integration of cfDNA testing into modern antenatal screening has made sex chromosome assessment possible from 10 weeks of gestation, and discordant fetal sex is now more commonly diagnosed prenatally, with a prevalence of approximately 1 in 1500-2000 pregnancies. Early detection of phenotype-genotype sex discordance is important as it may indicate an underlying genetic, chromosomal or biochemical condition and it also allows for time-critical postnatal treatment. The aim of this article is to review cfDNA and ultrasound diagnosis of fetal sex, identify possible causes of phenotype-genotype discordance and provide a systematic approach for clinicians when counseling and managing couples in this circumstance.

Prenatal detection and evaluation of differences of sex development

INTRODUCTION

Differences/disorders of sex development (DSD) can be detected at different ages, including prenatally. The recent implementation of prenatal genetic testing (including cell-free DNA) may affect the frequency and impact of prenatal diagnosis of DSD. Our aims were to (1) describe prenatal detection and evaluation of differences of sex development presenting to a multidisciplinary DSD clinic and (2) explore possible parental distress accompanying this evaluation.

MATERIALS AND METHODS

A retrospective chart review of mothers presenting prenatally, and patients presenting during infancy, to a multidisciplinary DSD clinic from 2013 to 2017 was conducted. Data extracted included demographics, final diagnoses, prenatal screening, prenatal evaluation, postnatal endocrine, genetic and radiologic testing, and clinician's notes on parent/patient distress.

RESULTS

Sixty-seven patients were identified; ten (15%) had prenatal detection of a suspected DSD. Of those, 4/10 were detected prenatally in the last study year alone. Within the prenatal group, 6/10 had cell-free DNA results discordant with ultrasound, 2/10 were detected by atypical genitalia on ultrasound, and 2/10 were detected through karyotyping performed for other indications. After birth, 3/10 patients were found to not have a DSD. Final diagnoses for the full study cohort are shown in the Summary Table, comparing prenatal versus postnatal presentation to our DSD clinic. Clinicians noted distress for most parents during the prenatal evaluation of a possible DSD, including one mother who reported suicidal thoughts.

DISCUSSION AND CONCLUSIONS

Prenatal suspicion of DSD can occur through discordant prenatal testing and has been observed at our clinic in recent years, in line with other recent studies. Contributing factors to these prenatal presentations could be increased referrals to the clinic, and increased use of non-invasive prenatal testing, which can lead to inaccurate or discordant sex identification. The prenatal suspicion of a potential DSD can be associated with parental distress, underscoring the need for adequate counseling for tests that determine fetal sex, including cell-free DNA.

Detection of SRY-positive46,XX male syndrome by the analysis of cell-free fetal DNA via non-invasive prenatal testing

We report a new case of 46,XX male syndrome that was detected following an anomalous result by non-invasive prenatal testing (NIPT) and a discrepancy between the fetal karyotype and the ultrasonographic investigation. With the increasing use of NIPT, more gender discordances can be identified prenatally and be amenable to early therapy.

Fetal sex discordance between noninvasive prenatal screening results and sonography: A single institution's experience and review of the literature

BACKGROUND

With the increasing availability of noninvasive prenatal screening (NIPS) and high-resolution ultrasound, more cases of sex discordance are being identified in routine clinical practice. This can be a source of much concern for families and clinicians. Knowledge about the limitations of NIPS and reasons for discordant results are critical for counseling parents.

AIMS

Here, we present three cases from a single tertiary care referral center. We also review the literature to address potential limitations of NIPS in correctly identifying fetal sex chromosomes.

MATERIALS AND METHODS

After Institutional Review Board approval, cases of discordant fetal sex were identified using ICD-9 and ICD-10 codes. In addition, departmental counseling database and cytogenetics laboratory logbooks were reviewed.

RESULTS

In our first case, a 37-year-old G4 P2012 underwent NIPS at 11 weeks gestation and Monosomy X (associated with Turner syndrome) was identified. Morphological sonographic assessment at 20 weeks gestation was consistent with a female fetus following an amniocentesis at 16 weeks that revealed normal 46, XX karyotype. During the third trimester, the patient was diagnosed with Stage IV invasive ductal carcinoma of the breast. Postnatal follow-up of the neonate was consistent with a phenotypic female. In the second case, a 22-year-old G2 P1001 obese female underwent NIPS at 14 weeks gestation and normal 46, XY karyotype was identified. Morphological sonographic assessment at 20 weeks was not consistent with a male fetus. The patient declined invasive testing. Postnatally, the karyotype was 46, XX and the neonate was phenotypically female. The reason for the discordant results was not identified. In the third case, a 25-year-old G1 P0 obese female underwent NIPS at 13 weeks gestation and normal 46, XY karyotype was identified. Morphological sonographic assessment at 20 weeks was indeterminate; however, follow-up at 24 weeks was consistent with a female fetus. The patient declined invasive prenatal testing. Postnatally, the karyotype was 46, XX, and the neonate was phenotypically female with uterus present on ultrasound. The reason for the discordant results was not identified.

DISCUSSION

Our cases demonstrate possible limitations of NIPS in correctly identifying sex chromosomes.

CONCLUSIONS

Providers and patients need to be aware of these limitations, and invasive diagnostic prenatal testing should be offered in cases of discordance between NIPS and sonographic sex assessment.

The importance of pre- and post-test counseling for prenatal cell-free DNA screening for common fetal aneuploidies

INTRODUCTION

Prenatal cell-free DNA screening for common fetal aneuploidies has rapidly changed the paradigm of prenatal care. Despite its advantages compared to conventional screening methods, its unexpectedly rapid implementation in clinical practice has generated several ethical and medical issues and misconceptions. Aggressive commercial marketing of cell-free DNA screening and media dissemination of misleading information have added confusion. Areas covered: This review provides an extensive update and will focus on the importance of pre-and post-test counseling for prenatal cell-free DNA screening not previously discussed extensively in the available literature. Additionally, we report cell-free DNA screening implementation in the largest obstetrical tertiary unit in Finland which is one of few countries that provides all prenatal screening methods free of charge for all women and has a very high uptake of first-trimester screening. This is not a systematical review, but rather a narrative overview which includes the most relevant and recent original publications and reviews covering this issue. Expert opinion: Despite being the most accurate method for screening of common fetal aneuploidies, the knowledge and counseling should be substantially improved. Cell-free DNA screening is not a replacement for diagnostic testing and its use in prenatal testing is complex and limited.

Discordant sex between fetal screening and postnatal phenotype requires evaluation

OBJECTIVE

Non-invasive prenatal screening (NIPS) utilizes circulating cell-free DNA (cfDNA) to screen for fetal genetic abnormalities. NIPS is the first widely-available prenatal screen to assess genotypic sex. Most pediatricians have limited familiarity with NIPS technology and potential etiologies of discordant results. Increased familiarity may provide diagnostic insight and improve clinical care.

STUDY DESIGN

We reviewed all patients with discordant genotypic fetal sex assessed by cfDNA and neonatal phenotypic sex referred to our medical center.

RESULT

Four infants with discordant cfDNA result and phenotypic sex were identified. Etiologies include vanishing twin syndrome, difference of sexual development, sex chromosome aneuploidy and maternal chimerism.

CONCLUSIONS

We present four cases illustrating potential etiologies of discordant cfDNA result and postnatal phenotypic sex. Unanticipated cfDNA results offer the perinatologist a unique opportunity for early diagnosis and targeted treatment of various conditions, many of which may not have otherwise been detected in the perinatal period.

Sex discordance identification following non-invasive prenatal testing

OBJECTIVE

The objectives of this study were to characterise genotype-phenotype discordance identified in the routine clinical setting and to explore the associated diagnostic and counselling challenges.

METHOD

Cases were derived from a cohort of pregnant women who attended a multisite specialist prenatal screening and ultrasound service for non-invasive prenatal testing by cell-free DNA analysis and midtrimester fetal morphology assessment.

RESULTS

Seven cases of genotype-phenotype discordance were identified from a cohort of 12 919 women between June 2013 and March 2017 (incidence 1/1845 pregnancies). A variety of disorders of sexual differentiation were subsequently diagnosed.

CONCLUSION

Sex chromosomes are the basis of sexual differentiation during embryonic development. Variations of the traditional XX or XY karyotype may result in conditions where the genotype is discordant with the phenotype. Detection of these conditions in the past typically occurred during adolescence, due to delayed puberty, or during adulthood, due to infertility. With the increasing availability of non-invasive prenatal testing and high-resolution ultrasound, more cases of genotype-phenotype sex discordance are being identified in routine clinical practice during early pregnancy. These discordant results present significant diagnostic and counselling challenges, and their potential should be included in increasingly complex pre-NIPT counselling.