Diagnostic approach to fetal microcephaly

Prevalence and timing of prenatal ultrasound findings in cytomegalovirus-infected pregnancies

INTRODUCTION

To investigate the prevalence and timing of prenatal neurosonographic abnormalities after primary cytomegalovirus seroconversion by the first trimester of pregnancy. The additional value of magnetic resonance imaging (MRI) and the correlation between cytomegalovirus viral load in amniotic fluid and adverse neonatal outcomes were evaluated.

MATERIAL AND METHODS

A retrospective study between 2006 and 2022 examined data from 440 women with amniocentesis for periconceptional and first-trimester cytomegalovirus seroconversion. Cases with positive amniocentesis and subsequent follow-up were included. Prenatal neurosonography, MRI, and clinical outcomes were analyzed.

RESULTS

Out of 190 women included, 37% (n = 70) presented with a normal neurosonography. Patients exhibiting abnormal neurosonography findings showed higher viral loads in amniotic fluid compared to those with a normal neurosonography (p = 0.002). In 26% (n = 49) the first abnormal ultrasound sign was already picked up at amniocentesis, and the most common ones were echogenic bowels (49%) and periventricular echogenicity (43%). With increasing gestational age, the likelihood of a new abnormal neurosonography finding decreases. MRI discovered additional abnormalities in 14% (n = 10).

CONCLUSIONS

The results highlight the importance of combining diagnostic modalities, from amniocentesis to biweekly ultrasound monitoring and subsequent MRI evaluation, to capture the chronological progression and subsequent outcome of congenital cytomegalovirus.

Prenatal assessment of brain malformations on neuroimaging: an expert panel review

Brain malformations represent a heterogeneous group of abnormalities of neural morphogenesis, often associated with aberrations of neuronal connectivity and brain volume. Prenatal detection of brain malformations requires a clear understanding of embryology and developmental morphology through the various stages of gestation. This expert panel review is written with the central aim of providing an easy-to-understand road map to improve prenatal detection and characterization of structural malformations based on the current understanding of normal and aberrant brain development. For every developmental stage, the utility of each available neuroimaging modality, including prenatal multiplanar neuro sonography, anatomical MRI and advanced MRI techniques, as well as further insights from post-mortem imaging, has been highlighted.

Small size, big problems: insights and difficulties in prenatal diagnosis of fetal microcephaly

Microcephaly is a sign, not a diagnosis. Its incidence varies widely due to the differences in the definition and the population being studied. It is strongly related to neurodevelopmental disorders. Differences in definitions and measurement techniques between fetuses and newborns pose a great challenge for the diagnosis and prognostication of fetal microcephaly. A false positive diagnosis can result (in countries where it is legal) in erroneous termination of pregnancy, where a false negative diagnosis might lead to the birth of a microcephalic newborn. Microcephaly in growth restricted fetuses deserves special attention and separate evaluation as it is an important prognostic factor, and not necessarily part of the general growth retardation. Several genetic syndromes incorporating microcephaly and intrauterine growth retardation (IUGR) are discussed. Deceleration of the head circumference (HC) growth rate even when the HC is still within normal limits might be the only clue for developing microcephaly and should be considered during fetal head growth follow up. Combining additional parameters such as a positive family history, associated anomalies, and new measurement parameters can improve prediction in about 50% of cases, and thus should be part of the prenatal workup. Advances in imaging modalities and in prenatal genetic investigation along with the emergence of new growth charts can also improve diagnostic accuracy. In this article, we review the different definitions and etiologies of fetal microcephaly, discuss difficulties in diagnosis, investigate the reasons for the low yield of prenatal diagnosis, and provide improvement suggestions. Finally, we suggest an updated algorithm that will aid in the diagnosis and management of fetal microcephaly.

Importance and application of WES in fetal genetic diagnostics: Identification of novel ASPM mutation in a fetus with microcephaly

Background

Prenatal whole exome sequencing (WES) approaches can provide genetic diagnosis with rapid turnaround time and high diagnostic rate when conventional tests are negative. Here we report a family with multiple pregnancy loss and with repeated occurrence of fetal microcephaly.

Methods and results

Because of positive family history and recurrent structural abnormality during the pregnancies that may lead postnatal neurodevelopmental consequences, WES analysis was indicated. Umbilical cord blood sampling was carried out and WES was performed using Twist Human Core Exome Kit and Illumina sequencing technology. The presence of pathogenic variants was confirmed by Sanger sequencing. WES analysis revealed a known pathogenic c.8506_8507delCA (p.Gln2836Glufs*35, rs587783280) and a novel pathogenic c.3134_3135delTC (p.Leu1045Glnfs*17) ASPM mutations in the fetus in compound heterozygous state. The c.3134_3135delTC has never been reported in the literature.

Conclusions

Our findings serve additional evidence that WES can be an efficient and relevant tool to diagnose certain genetic disorders with appropriate indication and to assess the recurrence risk of a disease. With the application of WES in combination with pre-implantation genetic tests, we can avoid the transmission of pathogenic mutations and we can achieve a decreased abortion rate in obstetric care.

[A pragmatic comparison of fetal biometry curves]

INTRODUCTION

The fetal biometrics charts recommended in France for ultrasound screening include measurements of head circumference (HC), biparietal diameter (BIP), abdominal circumference (AC) and femur length (FL). New international growth standards have been recommended since 2022. The aim of this work is to quantitatively describe the differences between these biometric curves.

METHODS

The biometry curves from the French College for Fetal Ultrasound, OMS and INTERGROWTH-21 are pragmatically compared based on their original quantile regression equations (superposition and quantification of differences in millimeters and in proportion) for different percentiles of clinical interest.

RESULTS

Compared with the new charts, CFEF underestimates HC<-3DS and AC<10eP. The proportions of differences between the CFEF and INTERGROWTH-21 or WHO curves always remained <5%. The proportions of difference of the 3rd percentile of HC and FL, 10th and 90th percentile of AC were always lower than 2%, 2%, 5% and 4% respectively, between OMS and INTERGROWTH-21.

CONCLUSION

The switch to prescriptive standards suggests an improvement in the detection of fetuses with AC<10th percentile, an improvement in the detection of prenatal onset microcephaly, with no argument for a decrease in the detection rate of severe constitutional bone disease or modification of obstetrical guidelines.

Feingold syndrome type 1: a rare cause of fetal microcephaly (prenatal diagnosis)

We report a case of fetal microcephaly found during the second trimester ultrasound and confirmed by further ultrasound scans and fetal MRI. The array comparative genomic hybridisation analysis of the fetus and the male parent showed a 1.5 Mb deletion overlapping the Feingold syndrome region, an autosomal dominant syndrome that can cause microcephaly, facial/hand abnormalities, mild neurodevelopmental delay and others. This case illustrates the need for a detailed investigation by a multidisciplinary team to provide prenatal counselling regarding a postnatal outcome to the parents and orient their decision towards the continuation or termination of pregnancy.

Advantages of current fetal neuroimaging and genomic technologies in prenatal diagnosis: A clinical case

The diagnosis of prenatal microcephaly, as well as the possibility of underlining a genetic cause, is becoming more frequent thanks to advances in prenatal imaging and parallel massive sequencing. One case of primary microcephaly in three sibs demonstrates how complementary diagnostic exams can help to diagnose and establish the etiology.

Fetal Brain Development: Regulating Processes and Related Malformations

This paper describes the contemporary state of knowledge regarding processes that regulate normal development of the embryonic–fetal central nervous system (CNS). The processes are described according to the developmental timetable: dorsal induction, ventral induction, neurogenesis, neuronal migration, post-migration neuronal development, and cortical organization. We review the current literature on CNS malformations associated with these regulating processes. We specifically address neural tube defects, holoprosencephaly, malformations of cortical development (including microcephaly, megalencephaly, lissencephaly, cobblestone malformations, gray matter heterotopia, and polymicrogyria), disorders of the corpus callosum, and posterior fossa malformations. Fetal ventriculomegaly, which frequently accompanies these disorders, is also reviewed. Each malformation is described with reference to the etiology, genetic causes, prenatal sonographic imaging, associated anomalies, differential diagnosis, complimentary diagnostic studies, clinical interventions, neurodevelopmental outcome, and life quality.

A Fetus with Congenital Microcephaly, Microphthalmia and Cataract Was Detected with Biallelic Variants in the OCLN Gene: A Case Report

Microcephaly and microphthalmia are both rare congenital abnormalities, while concurrently, these two are even rarer. The underlying etiology would be complex interplaying between heterogeneous genetic background and the environmental pathogens, particularly during critical periods of early tissue development. Here, we reported a prenatal case with microcephaly, microphthalmia, and bilateral cataracts detected by ultrasonography and confirmed by autopsy. Various routine infection-related tests and invasive genetic testing were negative. Whole genome sequencing of fetus and parents revealed OCLN gene defects may be associated with these multiple congenital abnormalities.

Is the ZIKV Congenital Syndrome and Microcephaly Due to Syndemism with Latent Virus Coinfection?

The emergence of the Zika virus (ZIKV) mirrors its evolutionary nature and, thus, its ability to grow in diversity or complexity (i.e., related to genome, host response, environment changes, tropism, and pathogenicity), leading to it recently joining the circle of closed congenital pathogens. The causal relation of ZIKV to microcephaly is still a much-debated issue. The identification of outbreak foci being in certain endemic urban areas characterized by a high-density population emphasizes that mixed infections might spearhead the recent appearance of a wide range of diseases that were initially attributed to ZIKV. Globally, such coinfections may have both positive and negative effects on viral replication, tropism, host response, and the viral genome. In other words, the possibility of coinfection may necessitate revisiting what is considered to be known regarding the pathogenesis and epidemiology of ZIKV diseases. ZIKV viral coinfections are already being reported with other arboviruses (e.g., chikungunya virus (CHIKV) and dengue virus (DENV)) as well as congenital pathogens (e.g., human immunodeficiency virus (HIV) and cytomegalovirus (HCMV)). However, descriptions of human latent viruses and their impacts on ZIKV disease outcomes in hosts are currently lacking. This review proposes to select some interesting human latent viruses (i.e., herpes simplex virus 2 (HSV-2), Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), human parvovirus B19 (B19V), and human papillomavirus (HPV)), whose virological features and co-exposition with ZIKV may provide evidence of the syndemism process, shedding some light on the emergence of the ZIKV-induced global congenital syndrome in South America.

Association of term isolated microcephaly with mode of delivery and perinatal outcome - a retrospective case-control analysis

Background

We aimed to evaluate the association of isolated fetal microcephaly measured by ultrasound prior to delivery at term with mode of delivery and perinatal outcome.

Methods

A single-center retrospective study was conducted in 2012–2016. Fetal microcephaly was defined as head circumference > 2 standard deviations of the mean for gestational age and sex. We compared the obstetric, delivery, and outcome parameters of women in whom ultrasound performed up to 10 days prior to term delivery showed isolated fetal microcephaly (study group) or normal head circumference (reference group). Exclusion criteria were intrauterine fetal death, birthweight below the 10th percentile, and antepartum cesarean delivery for any indication.

Results

Of 3677 women included in the study, 26 (0.7%) had a late ultrasound finding of isolated fetal microcephaly. Baseline characteristics were similar in the two groups except for estimated fetal weight based on abdominal circumference and biparietal diameter, which was lower in the microcephaly group (3209.8 ± 557.6 vs. 2685.8 ± 420.8 g, p < .001). There was no significant between-group difference in rate of vaginal operative deliveries (11.7% vs 14.8%, respectively, p = 0.372). The study group had no intrapartum cesarean deliveries compared to 6.3% of the reference group (NS). Compared to controls, neonates in the study group were smaller (3323.2 ± 432.2 vs. 2957.0 ± 330.4 g, p < .001), with lower birthweight percentile (60.5 ± 26.5 vs. 33.6 ± 21.5%, p < .001) and were more often males (48.2 vs. 90.0%, p < .001). No significant differences were noted in perinatal outcomes between the groups, including admission to neonatal intensive care unit, intraventricular hemorrhage, 5-min Apgar score < 7, asphyxia, seizures, and sepsis.

Conclusions

Isolated microcephaly in term fetuses is not advantageous for a vaginal delivery, nor does it does not pose a greater than normal risk of adverse perinatal outcome.

Prenatal Microcephaly and Hydrocephalus and Normal Heart Anatomy, Postnatal Diagnosis of Nijmegen Syndrome - Case Report

Nijmengen breakage syndrome is a rare autosomal condition mainly characterized by microcephaly. Patients are predisposed to malignancies due to combined immunodeficiency. The presented patient had prenatally diagnosed microcephaly with atypical ventriculomegaly of occipital horns. Fetal echocardiography showed a normal fetal heart anatomy. Diagnosis of Nijmengen syndrome was confirmed postnatally. The differential diagnosis of fetal microcephaly should take into account intrauterine infections, perinatal brain injury, congenital malformations or biological variants.