Fetal genital anomalies: an aid to diagnosis

Imaging in fetal genital anomalies

Genital anomalies are a heterogeneous group of congenital pathologies that have become increasingly relevant since the Chicago Consensus of 2005. Their postnatal diagnosis has developed significantly in the last two decades, while prenatal diagnosis seems to be underdeveloped, with few protocols available, fragmented scientific literature, and low diagnostic rates. This review aims to examine the current status of this subspecialty from the perspective of prenatal imaging. Indications for the evaluation of fetal genitalia can be divided into medical and non-medical reasons. Medical reasons include sex-linked disorders, detection of other anomalies, relevant family history, or multiple pregnancy. Non-medical reasons include parental request for sex disclosure. Disclosure of fetal sex may be associated with ethical, legal, and medical issues. The main imaging technology used is 2D ultrasound, although there are other complementary techniques such as 3D, MRI, or Color Doppler. Regarding working methodology, several authors have drawn attention to the lack of standardized protocols and guidelines. Most guidelines tend to limit their recommendations to study indications and ethical issues. Technical proposals, measurements, or working methods have not yet been standardized. Fetal sex determination is usually divided into early and late gestation. Early gestation is based on the sagittal sign. Late gestation is based on direct visualization. There are several measurements to describe male and female genitalia, such as penile length, bilabial diameter, or scrotal diameter. Prenatal diagnosis of genital pathologies presents some particularities such as the wide spectrum of phenotypes, the high frequency of associated deformities, or the time of diagnosis. Some of the most frequent pathologies are ambiguous genitalia, fetal sex discordance, hypospadias, micropenis, clitoromegaly, ovarian cysts, hydro(metro)colpos, and cloacal anomalies. Higher-quality studies and direction from scientific societies through the implementation of clinical guidelines are needed.

Clinical spectrum of female genital malformations in prenatal diagnosis

Introduction

Fetal genital malformations represent a rare and heterogeneous group of congenital malformations of the disorders of sexual development (DSD) spectrum.

Methods

A thorough literature review on the main topics in the prenatal approach towards DSD was conducted.

Results

First, a thorough overview on prenatal characteristics of the most common fetal genital malformations of ovaries, uterus and external genitalia, and second, a standardized approach for differential diagnosis in the presence of direct and indirect prenatal signs of DSDs.

Conclusions

This review is mainly directed towards the aspects of female genital malformations with  aspects of male DSD explained as well to aid in the prenatal differential diagnosis.

Prenatal Diagnosis and Classification of Fetal Hypospadias: The Role and Value of Magnetic Resonance Imaging

BACKGROUND

Prenatal diagnosis and classification of hypospadias are difficult and of value for management during perinatal and neonatal periods. The conventional approach for prenatal diagnosis of hypospadias is ultrasound; however, this technique may be inconclusive in certain cases, which prompts for further exploration with magnetic resonance imaging (MRI).

PURPOSE

To investigate the role of MRI in the prenatal diagnosis and classification of fetuses with hypospadias.

STUDY TYPE

Retrospective.

POPULATION

Thirty-five fetuses (median gestational age = 37, range 24-39 weeks) with possible hypospadias.

FIELD STRENGTH/SEQUENCE

Single-shot fast spin echo T2-weighted imaging, fast imaging employing steady-state acquisition (FIESTA), and three-dimensional FIESTA acquired at 1.5 T.

ASSESSMENT

Diagnosis and classification of hypospadias using MRI were performed by three experienced radiologists based on MRI features, including a short penile shaft, abnormal penile tip, penile curvature, bifid scrotum, "tulip sign," and penoscrotal transposition. The accuracy of MRI in the diagnosis and classification of hypospadias was assessed in comparison to postnatal clinical diagnosis. The interobserver agreement between radiologists was also assessed.

STATISTICAL TESTS

Kendall's W test was applied to assess the interobserver agreement between radiologists. Taking postnatal clinical diagnosis as the reference standard, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated.

RESULTS

Of the 35 fetuses, 24 cases were confirmed as hypospadias through postnatal clinical diagnosis. The interobserver agreement between radiologists was substantial (Kendall's W = 0.781, P < 0.001). Of the 24 confirmed cases (13 cases of severe hypospadias and 11 cases of mild hypospadias), 22 cases were correctly diagnosed by MRI. The accuracy of MRI in the diagnosis of hypospadias, severe hypospadias, and mild hypospadias was 85.71%, 82.86%, and 80.00%, respectively.

DATA CONCLUSION

MRI has good performance in the diagnosis of fetal hypospadias. In addition, MRI could help evaluate the severity of fetal hypospadias.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY: Stage 2.

[Genital abnormalities: Contextualization of a neglected area in prenatal diagnosis]

OBJECTIVE

To reflect on how the area of genital abnormalities has fallen behind in prenatal diagnosis.

METHODS

Based on the thesis that prenatal diagnosis of genital abnormalities has scarcely developed, a comparison with other areas of prenatal diagnosis and with its postnatal counterpart is presented; different explanations for this situation are examined; and a reflection is presented on ways to expand this field of knowledge.

CONCLUSIONS

Compared to other disciplines, prenatal diagnosis of genital abnormalities finds itself lagging behind in terms of diagnostic tools, management protocols and scientific literature. Potential causes include a perception of low prevalence and limited importance, or exploration challenges. Integration of current knowledge, together with the acquisition of the appropriate tools and translation to clinical medicine, would be a way to make this discipline stronger.

Sonographic measure techniques of fetal penile length

Postnatal penile length is a reliable, standardized, and widely used marker for the diagnosis of genitourinary pathology, as well as genetic and hormonal disorders. In contrast, prenatal diagnosis has not been developed equally and there is a lack of relevant literature. Our objective is to review the studies on fetal penile length, and apply findings to clinical practice. Although the most used technique is the outer penile length, there is no consensus regarding the appropriate technique for prenatal measurement. Several reports have provided reference data with high correlation. However, important issues like poor correlation with post-natal measures or presence of confounding variables are still present. Diagnosis of both a micropenis and macropenis can indicate related pathologies, and this information may benefit parental counseling and facilitate fetal management. Therefore, it is necessary to carry out prospective studies that provide reliable normative data.

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 imaging of genital defects: clinical spectrum and predictive factors for severe forms

OBJECTIVES

To report the clinical spectrum of genital defects diagnosed before birth, identify predictive factors for severe phenotypes at birth, and determine the rate of associated malformations.

PATIENTS AND METHODS

A retrospective study (2008-2017) of 4580 fetuses, identified prenatally with abnormalities evaluated by our Reference Center for Fetal Medicine, included cases with fetal sonographic findings of abnormal genitalia or uncertainty of fetal sex determination. Familial, prenatal and postnatal data were collected via a standardised questionnaire.

RESULTS

In all, 61 fetuses were included. The positive predictive value (PPV) of the prenatal diagnosis of genital defects was 90.1%. Most cases were 46,XY-undervirilized boys, 42 cases (68.8%), which included 29 with mid-penile or posterior hypospadias, nine with anterior hypospadias, and epispadias, micropenis, scrotal transposition, and buried penis (one each). In all, 46,XX-virilized girls were identified in seven cases (11.5%), which included four with congenital adrenal hyperplasia, two with isolated clitoromegaly, and one with ovotestis. Other defects included prune belly syndrome and persistent cloaca (six cases). Early detection during the second trimester (58.1% vs 18.8%, P = 0.03), intra-uterine growth restriction (IUGR) (45.2% vs 9.1%, P = 0.06), and curvature of the penis (38.7% vs 0%, P = 0.02), were more frequently related to severe defects in male newborns. Associated malformations (14 cases, 22.9%) and genetic defects (six) were frequent in undervirilized boys.

CONCLUSION

Prenatal imaging of genital defects leads to a wide range of phenotypes at birth. Its PPV is high and extra-urinary malformations are frequent. Early diagnosis during the second trimester, associated IUGR, and curvature of the genital tubercle, should raise suspicion of a severe phenotype and may justify delivery near a multidisciplinary disorders/differences of sex development team.

Antenatal Diagnosis of Dizygotic, Monochorionic Twins Following IVF/ICSI

Monochorionic twins are usually monozygotic and thus usually have the same sex. A case of monochorionic diamniotic twins following IVF/ICSI and laser treatment of the zona pellucida ("assisted hatching") is presented in which partial embryo amalgamation appears to have occurred. Discordant sex between the twins was suspected on detailed antenatal ultrasound at 13 + 3 weeks gestation and was confirmed on subsequent examinations. The sexual phenotype at birth was female for one twin and male for the other. Placental histology confirmed the monochorionic, diamniotic situation. Cytogenetic analysis of both twins was carried out postpartum on various tissues. On karyotyping of blood lymphocytes the male and female twins each had one mosaic of male and female cells. Oral mucosal cells showed normal male and female karyotypes respectively. Analysis of urothelium showed a normal result for the male infant, and a weak gonosomal mosaic with an XX and XY constellation for the female infant. At least for blood lymphocytes, a diagnosis of chimerism was proven.

Prenatal management of disorders of sex development

Disorders of sex development (DSD) rarely present prenatally but, as they are very complex conditions, management should be directed by highly specialised medical teams to allow consideration of all aspects of diagnosis, treatment and ethical issues. In this brief review, we present an overview of the prenatal presentation and management of DSD, including the sonographic appearance of normal genitalia and methods of determining genetic sex, the prenatal management of pregnancies with the unexpected finding of genital ambiguity on prenatal ultrasound and a review of the prenatal management of pregnancies at high risk of DSD. As this is a rapidly developing field, management options will change over time, making the involvement of clinical geneticists, paediatric endocrinologists and urologists, as well as fetal medicine specialists, essential in the care of these complex pregnancies. The reader should also bear in mind that local social, ethical and legal aspects may also influence management.

Penile biometry on prenatal magnetic resonance imaging

OBJECTIVE

In view of the implementation of magnetic resonance imaging (MRI) as an adjunct to ultrasonography in prenatal diagnosis, this study sought to demonstrate normal penile growth on prenatal MRI.

METHODS

This was a retrospective study of MRI of 194 male fetuses (18-34 weeks' gestation) with normal anatomy or minor abnormalities. On sagittal T2-weighted MRI sequences, we measured penile length from the glans tip to the scrotal edge (outer length) and from the glans tip to the symphyseal border (total length). Descriptive statistics, as well as correlation and regression analysis, were used to evaluate penile length in relation to gestation. T-tests were calculated to compare mean outer/total length on MRI with published ultrasound data.

RESULTS

Mean length values, including 95% CIs and percentiles, were defined. Penile length as a function of gestational age was expressed by the following regression equations: outer mean length = - 5.514 + 0.622 × gestational age in weeks; total mean length = - 8.865 + 1.312× gestational age in weeks. The correlation coefficients, r = 0.532 and r = 0.751, respectively, were statistically significant (P < 0.001). Comparison of outer penile length on MRI with published ultrasound penile length data showed no significant differences, while total penile length on MRI was significantly greater than ultrasound penile length (P < 0.001).

CONCLUSION

Our MRI results provide a reference range of fetal penile length, which, in addition to ultrasonography, may be helpful in the identification of genital anomalies. Outer penile length on MRI is equivalent to penile length measured on ultrasound, whereas total length is significantly greater.

Female external genitalia on fetal magnetic resonance imaging

OBJECTIVES

To characterize the normal development of the female external genitalia on fetal magnetic resonance imaging (MRI).

METHODS

This retrospective study included MRI examinations of 191 female fetuses (20-36 gestational weeks) with normal anatomy or minor abnormalities, following suspicion of anomalies on prenatal ultrasound examination. Using a 1.5-Tesla unit, the bilabial diameter was measured on T2-weighted sequences. Statistical description, as well as correlation and regression analyses, was used to evaluate bilabial diameter in relation to gestational age. MRI measurements were compared with published ultrasound data. The morphological appearance and signal intensities of the external genitalia were also assessed.

RESULTS

Mean bilabial diameters, with 95% CIs and percentiles, were defined. The bilabial diameter as a function of gestational age was expressed by the regression equation: bilabial diameter = - 11.336 + 0.836 × (gestational age in weeks). The correlation coefficient, r = 0.782, was statistically significant (P < 0.001). Bilabial diameter on MRI was not significantly different from that on ultrasound (P < 0.001). In addition, on MRI we observed changes in morphology of the external genitalia and in signal intensities with increasing gestational age.

CONCLUSIONS

We have provided a reference range of fetal bilabial diameter on MRI, which, in addition to ultrasound findings, may be helpful in the identification of genital anomalies.

Abnormalities of the penis in utero--hypospadias on fetal MRI

OBJECTIVE

To demonstrate the visualization of penile abnormalities on fetal magnetic resonance imaging (MRI).

METHODS

This retrospective study included five fetuses (25+0 to 31+6 gestational weeks) with penile abnormalities, positively depicted on fetal MRI, using prenatal ultrasonography (US) as a standard of reference. On MRI, the penis, as well as the scrotum and testicles, were evaluated. All fetal organs were reviewed to define penile abnormalities as isolated or in association with other anomalies. Furthermore, US and MRI findings were compared.

RESULTS

Posterior hypospadias were demonstrated in all five fetuses, and abnormal testicular descent in two. Associated anomalies were present in all five fetuses on MRI, including abdominal/urogenital pathologies in four; brain pathologies in three; and craniofacial, cardiac, musculoskeletal, pathologies each in one fetus, and intrauterine growth retardation in one fetus. Compared to US, additional MRI findings were shown in four of five fetuses.

CONCLUSIONS

Our MRI results demonstrate the visualization of fetal penile abnormalities and associated pathologies, which may provide information for perinatal management. MRI may show additional findings compared to prenatal US in certain cases.