Population-based microcephaly surveillance in the United States, 2009 to 2013: An analysis of potential sources of variation

Systematic review and meta-analysis of the association between young maternal age and fetal abnormalities

Fetal anomalies among young women and adolescents pose major public health concerns. This systematic review aims to elucidate the relationship between young maternal age and the incidence of fetal abnormalities. According to the systematic review and meta-analysis PRISMA protocol, cohort, cross-sectional and case-control studies were scrutinized to include 80,393,450 participants across diverse regions. The meta-analysis utilized Odds Ratios (OR) as the effect measure, adopting a random-effects model. The screening process involved 157 selected and verified manuscripts, which ultimately resulted in the final inclusion of 20 studied in the meta-analysis. The criterion for young maternal age was the age of ≤ 20 years. The meta-analysis revealed a pooled OR of 0.93 (95% CI: 0.82-1.05, p = 0.252), indicating no statistically significant association between young maternal age (≤ 20 years) and fetal anomalies. However, considerable heterogeneity (I² = 96.21%) was noted, prompting the use of a random-effects model to derive the reported results. The meta-analysis did not find statistically significant differences in the occurrence of congenital anomalies in fetuses of younger women than in overall population. Although due to significant heterogeneity of the analyzed studies, and a risk of bias, caution should be exercised when interpreting the results, further investigation may be warranted to understand the relationship between maternal age and risk of fetal anomalies. Nevertheless, the study shows significant differences, which diminish in collective analysis, suggests that factors beyond age may be influential. Specifically, the limited access to or quality of healthcare in certain regions could be a more critical factor than maternal age itself.

Microcephaly in Infants: A Retrospective Cohort Study from Turkey

Objective

Microcephaly (MC) is a clinical finding mostly reflecting deficiency of brain growth. The aim of this retrospective cohort study was to assess risk factors and follow-up features of children with MC.

Methods

Children’s personal health records (n=7580) followed between 2002 and 2020 in the Unit of a Well Child Clinic were assessed retrospectively. The case group comprised children with MC. MC was defined as head circumference (HC) standard deviation score (SDS) value ≤-2 SDS. Age and sex-matched children with normal HC were selected as the control group.

Results

Children with MC (n=49) had more disadvantaged sociodemographic characteristics, such as young maternal and paternal age and low maternal and paternal education. Breastfeeding was more common among controls (n=98). Resolution of MC was observed in 26 (53.1%) children with MC, whether it was mild (HC SDS between -2 and -2.9) or severe (HC SDS ≤3). Children with persistent MC had poorer developmental milestones than controls and cases with resolution. Sociodemographic features or developmental milestones in mild and severe MC did not differ.

Conclusion

These results suggest that the use of a definition of MC of ≤-2 SDS would be appropriate in order not to miss cases on follow-up. Greater sociodemographic equality may prevent some cases of MC. Further studies are needed evaluating socioeconomic factors on MC.

Prenatal exposure to antiseizure medications and fetal growth: a population-based cohort study from the Nordic countries

Background

The short- and long-term consequences of restricted fetal growth cause considerable concern, and how prenatal exposure to different antiseizure medications (ASMs) affects fetal growth remains uncertain.

Methods

This was a population-based cohort study of liveborn singleton children born in Denmark, Finland, Iceland, Norway, and Sweden from 1996 to 2017. Prenatal exposure was defined as maternal filling of prescriptions for ASM during pregnancy registered in national prescription registries and primary outcomes were adjusted odds ratios (aORs) of microcephaly or being born small for gestational age.

Findings

We identified 4,494,918 children (males: 51.3%, 2,306,991/4,494,918), including 38,714 (0.9%) children of mothers with epilepsy. In the overall population, prenatal monotherapy exposure with carbamazepine (aOR: 1.25 (95% CI: 1.12-1.40)), pregabalin (aOR: 1.16 (95% CI: 1.02-1.31)), oxcarbazepine (aOR: 1.48 (95% CI: 1.28-1.71)), clonazepam (aOR: 1.27 (95% CI: 1.10-1.48)), and topiramate (aOR: 1.48 (95% CI: 1.18-1.85)) was associated with risk of being born small for gestational age, and carbamazepine was associated with microcephaly (aOR: 1.43 (95% CI: 1.17-1.75)). In children of mothers with epilepsy, prenatal exposure to carbamazepine (aOR: 1.27 (95% CI: 1.11-1.47)), oxcarbazepine (aOR: 1.42 (95% CI: 1.18-1.70)), clonazepam (aOR: 1.40 (95% CI: 1.03-1.89)), and topiramate (aOR: 1.86 (95% CI: 1.36-2.54)) was associated with being born small for gestational age; carbamazepine, with microcephaly (aOR: 1.51 (95% CI: 1.17-1.95)). No associations with small for gestational age and microcephaly were identified after prenatal exposure to lamotrigine, valproate, gabapentin, levetiracetam, phenobarbital, acetazolamide, phenytoin, clobazam, primidone, zonisamide, vigabatrin, ethosuximide and lacosamide, but except for lamotrigine, valproate, gabapentin, and levetiracetam, numbers of exposed children were small.

Interpretation

Prenatal exposure to carbamazepine, oxcarbazepine, clonazepam, and topiramate was associated with increased risk of being born small for gestational age in both the overall population and in children of women with epilepsy suggesting that prenatal exposure to these drugs is associated with fetal growth restriction.

Funding

The NordForsk Nordic Program on Health and Welfare (83539), the Independent Research Fund Denmark (1133-00026B), the Danish Epilepsy Association, the Central Denmark Region, the Novo Nordisk Foundation (NNF16OC0019126 and NNF22OC0075033), and the Lundbeck Foundation (R400-2022-1205).

Louis AM, Agopian AJ. Scientific impact of the National Birth Defects Prevention Network multistate collaborative publications

BACKGROUND

Given the lack of a national, population-based birth defects surveillance program in the United States, the National Birth Defects Prevention Network (NBDPN) has facilitated important studies on surveillance, research, and prevention of major birth defects. We sought to summarize NBDPN peer-reviewed publications and their impact.

METHODS

We obtained and reviewed a curated list of 49 NBDPN multistate collaborative publications during 2000-2022, as of December 31, 2022. Each publication was reviewed and classified by type (e.g., risk factor association analysis). Key characteristics of study populations and analytic approaches used, along with publication impact (e.g., number of citations), were tabulated.

RESULTS

NBDPN publications focused on prevalence estimates (N = 17), surveillance methods (N = 11), risk factor associations (N = 10), mortality and other outcomes among affected individuals (N = 6), and descriptive epidemiology of various birth defects (N = 5). The most cited publications were those that reported on prevalence estimates for a spectrum of defects and those that assessed changes in neural tube defects (NTD) prevalence following mandatory folic acid fortification in the United States.

CONCLUSIONS

Results from multistate NBDPN publications have provided critical information not available through other sources, including US prevalence estimates of major birth defects, folic acid fortification and NTD prevention, and improved understanding of defect trends and surveillance efforts. Until a national birth defects surveillance program is established in the United States, NBDPN collaborative publications remain an important resource for investigating birth defects and informing decisions related to health services planning of secondary disabilities prevention and care.

Prevalence of congenital anomalies according to maternal race and ethnicity, Texas, 1999-2018

BACKGROUND

Few studies of congenital anomalies provide prevalence estimates stratified by maternal race/ethnicity. We sought to determine whether the prevalence of a broad spectrum of anomalies varies among offspring of women from different race/ethnic groups.

METHODS

We obtained information on cases with anomalies from the population-based Texas Birth Defects Registry, and denominator data on livebirths among Texas residents during 1999-2018 from the Texas Center for Health Statistics. We estimated the prevalence ratio (PR) and 95% confidence interval (CI) of N = 145 anomalies among offspring of Hispanic and non-Hispanic Black relative to non-Hispanic White women using Poisson regression, adjusting for maternal age, education, body mass index, and previous livebirths. We performed a two-stage analysis with a Bonferroni-adjusted p < 1.7 × 10-4 in the initial screening phase to identify anomalies with statistically significant variation.

RESULTS

There were 7,698,768 livebirths and 1,187,385 anomalies diagnosed in 368,393 cases. The prevalence of any monitored congenital anomaly was similar among offspring of non-Hispanic White (referent), non-Hispanic Black (PR 0.98, CI 0.96-1.00), and Hispanic (PR 0.95, CI 0.93-0.96) women. We observed statistically significant racial/ethnic variation for 42 anomalies. Marked differences were observed when comparing offspring of non-Hispanic Black to non-Hispanic White women with respect to polydactyly (PR 4.38, CI 4.07-4.72), pyloric stenosis (PR 0.34, CI 0.29-0.40), and aortic valve atresia/stenosis (PR 0.51, CI 0.36-0.72).

CONCLUSIONS

Birth prevalence of many major congenital anomalies varies by maternal race and ethnicity. While the reasons for these differences are likely multifactorial, a thorough understanding of racial and ethnic disparities is useful to stimulate etiologic research.

Transcription factors in microcephaly

Higher cognition in humans, compared to other primates, is often attributed to an increased brain size, especially forebrain cortical surface area. Brain size is determined through highly orchestrated developmental processes, including neural stem cell proliferation, differentiation, migration, lamination, arborization, and apoptosis. Disruption in these processes often results in either a small (microcephaly) or large (megalencephaly) brain. One of the key mechanisms controlling these developmental processes is the spatial and temporal transcriptional regulation of critical genes. In humans, microcephaly is defined as a condition with a significantly smaller head circumference compared to the average head size of a given age and sex group. A growing number of genes are identified as associated with microcephaly, and among them are those involved in transcriptional regulation. In this review, a subset of genes encoding transcription factors (e.g., homeobox-, basic helix-loop-helix-, forkhead box-, high mobility group box-, and zinc finger domain-containing transcription factors), whose functions are important for cortical development and implicated in microcephaly, are discussed.

The impact of TP53 activation and apoptosis in primary hereditary microcephaly

Autosomal recessive primary microcephaly (MCPH) is a constellation of disorders that share significant brain size reduction and mild to moderate intellectual disability, which may be accompanied by a large variety of more invalidating clinical signs. Extensive neural progenitor cells (NPC) proliferation and differentiation are essential to determine brain final size. Accordingly, the 30 MCPH loci mapped so far (MCPH1-MCPH30) encode for proteins involved in microtubule and spindle organization, centriole biogenesis, nuclear envelope, DNA replication and repair, underscoring that a wide variety of cellular processes is required for sustaining NPC expansion during development. Current models propose that altered balance between symmetric and asymmetric division, as well as premature differentiation, are the main mechanisms leading to MCPH. Although studies of cellular alterations in microcephaly models have constantly shown the co-existence of high DNA damage and apoptosis levels, these mechanisms are less considered as primary factors. In this review we highlight how the molecular and cellular events produced by mutation of the majority of MCPH genes may converge on apoptotic death of NPCs and neurons, via TP53 activation. We propose that these mechanisms should be more carefully considered in the alterations of the sophisticated equilibrium between proliferation, differentiation and death produced by MCPH gene mutations. In consideration of the potential druggability of cell apoptotic pathways, a better understanding of their role in MCPH may significantly facilitate the development of translational approaches.

Safety of COVID-19 vaccines during pregnancy: A systematic review and meta-analysis

BACKGROUND

Assessment of COVID-19 vaccines safety during pregnancy is urgently needed.

METHODS

We conducted a systematic review and meta-analysis to evaluate the safety of COVID-19 vaccines, including their components and technological platforms used in other vaccines during pregnancy and animal studies to complement direct evidence. We searched literature databases from its inception to September 2021 without language restriction, COVID-19 vaccine websites, and reference lists of other systematic reviews and the included studies. Pairs of reviewers independently selected, data extracted, and assessed the risk of bias of the studies. Discrepancies were resolved by consensus. (PROSPERO CRD42021234185).

RESULTS

We retrieved 8,837 records from the literature search; 71 studies were included, involving 17,719,495 pregnant persons and 389 pregnant animals. Most studies (94%) were conducted in high-income countries, were cohort studies (51%), and 15% were classified as high risk of bias. We identified nine COVID-19 vaccine studies, seven involving 309,164 pregnant persons, mostly exposed to mRNA vaccines. Among non-COVID-19 vaccines, the most frequent exposures were AS03 and aluminum-based adjuvants. A meta-analysis of studies that adjusted for potential confounders showed no association with adverse outcomes, regardless of the vaccine or the trimester of vaccination. Neither the reported rates of adverse pregnancy outcomes nor reactogenicity exceeded expected background rates, which was the case for ASO3- or aluminum-adjuvanted non-COVID-19 vaccines in the proportion meta-analyses of uncontrolled studies/arms. The only exception was postpartum hemorrhage after COVID-19 vaccination (10.40%; 95% CI: 6.49-15.10%), reported by two studies; however, the comparison with non-exposed pregnant persons, available for one study, found non-statistically significant differences (adjusted OR 1.09; 95% CI 0.56-2.12). Animal studies showed consistent results with studies in pregnant persons.

CONCLUSION

We found no safety concerns for currently administered COVID-19 vaccines during pregnancy. Additional experimental and real-world evidence could enhance vaccination coverage. Robust safety data for non-mRNA-based COVID-19 vaccines are still needed.

Incidence, aetiology and neurodisability associated with severe microcephaly: a national surveillance study

OBJECTIVE

To determine the incidence, causes and neurodevelopmental impact of severe microcephaly (head circumference <-3SD) up to age 2 years.

DESIGN

Binational active paediatric surveillance study undertaken in 2017-2018 to identify and characterise new diagnoses of severe microcephaly.

SETTING

UK and Ireland.

PARTICIPANTS

Infants aged under 12 months at diagnosis.

INTERVENTIONS

Observational study.

MAIN OUTCOME MEASURES

Incidence, aetiology and neurodevelopmental outcomes at age 2 years.

RESULTS

Fifty-nine infants met the case definition, of whom 30 (51%) were girls; 24 (41%) were born preterm (<37 weeks' gestation); and 34 (58%) were of 'white' ethnicity. Eight (14%) children died before 12 months of age. Incidence of severe microcephaly was 5.5 per 100 000 infants (95% CI 4.0 to 7.3). Higher relative risk (RR) was associated with preterm birth (RR 7.7, 95% CI 3.8 to 15.1) and British Asian ethnicity (RR 3.6, 95% CI 1.6 to 7.8). Microcephaly was mainly due to genetic causes (59%), brain ischaemia/hypoxia (10%) and congenital infection (8%), and 19% remained undetermined. Each child was referred on average to eight specialists, and 75% had abnormal brain imaging. By 2 years of age, 55 children experienced neurodevelopmental abnormalities, including feeding problems (68%), motor delay (66%), visual impairment (37%), hearing loss (24%) and epilepsy (41%).

CONCLUSIONS

Although severe microcephaly is uncommon, it is associated with high mortality, complex multimorbidity and neurodisability, thus representing a significant ongoing burden for families and healthcare services. Potentially preventable causes include preterm birth, hypoxic/ischaemic brain injury and congenital infections. Clinical guidelines are essential to standardise aetiological investigation and optimise multidisciplinary management.

Survival of infants and children born with severe microcephaly, Texas, 1999-2015

BACKGROUND

Severe microcephaly is a brain reduction defect where the delivery head circumference is <3rd percentile for gestational age and sex with subsequent lifelong morbidities. Our objective was to evaluate survival among 2,704 Texas infants with severe microcephaly delivered 1999-2015.

METHODS

Infants with severe microcephaly from the Texas Birth Defects Registry were linked to death certificates and the national death index. Survival estimates, hazard ratios (HR) and confidence intervals (CI) were calculated using the Kaplan-Meier method and Cox proportional hazards models stratified by presence versus absence of co-occurring defects.

RESULTS

We identified 496 deaths by age 4 years; most (42.9%) occurred in the neonatal period, and another 39.9% died by 1 year of age. Overall infant survival was 84.8%. Lowest infant survival subgroups included those with chromosomal/syndromic conditions (66.1%), very preterm deliveries (63.9%), or co-occurring critical congenital heart defects (44.0%). Among infants with severe microcephaly and a chromosomal/syndromic co-occurring defect, the risk of death was nearly three-fold higher among those with: proportionate microcephaly (i.e., small baby overall), relative to non-proportionate (HR = 2.84, 95% CI = 2.17-3.71); low-birthweight relative to normal (HR = 2.72, 95% CI = 1.92-3.85); critical congenital heart defects (CCHD) relative to no CCHD (HR = 2.90, 95% CI = 2.20-3.80). Trisomies were a leading underlying cause of death (27.5%).

CONCLUSIONS

Overall, infants with severe microcephaly had high 4-year survival rates which varied by the presence of co-occurring defects. Infants with co-occurring chromosomal/syndromic anomalies have a higher risk of death by age one than those without any co-occurring birth defects.

Gene-environment interactions in the pathogenesis of common craniofacial anomalies

Craniofacial anomalies often exhibit phenotype variability and non-mendelian inheritance due to their multifactorial origin, involving both genetic and environmental factors. A combination of epidemiologic studies, genome-wide association, and analysis of animal models have provided insight into the effects of gene-environment interactions on craniofacial and brain development and the pathogenesis of congenital disorders. In this chapter, we briefly summarize the etiology and pathogenesis of common craniofacial anomalies, focusing on orofacial clefts, hemifacial microsomia, and microcephaly. We then discuss how environmental risk factors interact with genes to modulate the incidence and phenotype severity of craniofacial anomalies. Identifying environmental risk factors and dissecting their interaction with different genes and modifiers is central to improved strategies for preventing craniofacial anomalies.

ANKLE2-related microcephaly: A variable microcephaly syndrome resembling Zika infection

OBJECTIVE

This study delineates the clinical and molecular spectrum of ANKLE2-related microcephaly (MIC), as well as highlights shared pathological mechanisms between ANKLE2 and the Zika virus.

METHODS

We identified 12 individuals with MIC and variants in ANKLE2 with a broad range of features. Probands underwent thorough phenotypic evaluations, developmental assessments, and anthropometric measurements. Brain imaging studies were systematically reviewed for developmental abnormalities. We functionally interrogated a subset of identified ANKLE2 variants in Drosophila melanogaster.

RESULTS

All individuals had MIC (z-score ≤ -3), including nine with congenital MIC. We identified a broad range of brain abnormalities including simplified cortical gyral pattern, full or partial callosal agenesis, increased extra-axial spaces, hypomyelination, cerebellar vermis hypoplasia, and enlarged cisterna magna. All probands had developmental delays in at least one domain, with speech and language delays being the most common. Six probands had skin findings characteristic of ANKLE2 including hyper- and hypopigmented macules. Only one individual had scalp rugae. Functional characterization in Drosophila recapitulated the human MIC phenotype. Of the four variants tested, p.Val229Gly, p.Arg236*, and p.Arg536Cys acted as partial-loss-of-function variants, whereas the c.1421-1G>C splicing variant demonstrated a strong loss-of-function effect.

INTERPRETATION

Deleterious variants in the ANKLE2 gene cause a unique MIC syndrome characterized by congenital or postnatal MIC, a broad range of structural brain abnormalities, and skin pigmentary changes. Thorough functional characterization has identified shared pathogenic mechanisms between ANKLE2-related MIC and congenital Zika virus infection. This study further highlights the importance of a thorough diagnostic evaluation including molecular diagnostic testing in individuals with MIC.

Congenital anomalies and maternal age: A systematic review and meta-analysis of observational studies

INTRODUCTION

Several studies have reported on the maternal age-associated risks of congenital anomalies. However, there is a paucity of studies with comprehensive review of anomalies. We aimed to quantify the risk of birth defects in children born to middle-aged mothers compared with that in children born to young or older mothers.

MATERIAL AND METHODS

We classified maternal ages into three groups: young (<20 years old), middle (20-34 years old) and older age (≥35 years old). Observational studies that met our age criteria were eligible for inclusion. The articles searched using the Embase and MEDLINE databases were those published from 1989 to January 21, 2021. The Newcastle-Ottawa scale was used to assess the risk of bias. If heterogeneity exceeded 50%, the random effect method was used; otherwise, the fixed-effect method was used. Prospero registration number: CRD42021235229.

RESULTS

We included 15 cohort, 14 case-control and 36 cross-sectional studies. The pooled unadjusted odds ratio (95% CI) of any congenital anomaly was 1.64 (1.40-1.92) and 1.05 (0.95-1.15) in the older and young age groups, respectively (very low quality of evidence). The pooled unadjusted odds ratio of chromosomal anomaly was 5.64 (5.13-6.20) and 0.69 (0.54-0.88) in the older and young age groups, respectively. The pooled unadjusted odds ratio of non-chromosomal anomaly was 1.09 (1.01-1.17) and 1.10 (1.01-1.21) in the older and young age groups, respectively (very low quality of evidence). The incidence of abdominal wall defects was increased in children of women in the young maternal age group.

CONCLUSIONS

We identified that very low quality evidence suggests that women in the older maternal age group had increased odds of having children with congenital anomalies compared with those in the 20-34 year age group. There was no increase in odds of children with congenital anomalies in women of <20 year age group except for abdominal defects compared with those in the 20-34 year age group. The results stem from very low quality evidence with no adjustment of confounders.

Identifying possible inaccuracy in reported birth head circumference measurements among infants in the US Zika Pregnancy and Infant Registry

BACKGROUND

The US Zika Pregnancy and Infant Registry (USZPIR) monitors infants born to mothers with confirmed or possible Zika virus infection during pregnancy. The surveillance case definition for Zika-associated birth defects includes microcephaly based on head circumference (HC).

METHODS

We assessed birth and follow-up data from infants with birth HC measurements <3rd percentile and birthweight ≥10th percentile to determine possible misclassification of microcephaly. We developed a schema informed by literature review and expert opinion to identify possible HC measurement inaccuracy using HC growth velocity and longitudinal HC measurements between 2 and 12 months of age. Two or more HC measurements were required for assessment. Inaccuracy in birth HC measurement was suspected if growth velocity was >3 cm/month in the first 3 months or HC was consistently >25th percentile during follow-up.

RESULTS

Of 6,799 liveborn infants in USZPIR, 351 (5.2%) had Zika-associated birth defects, of which 111 had birth HC measurements <3rd percentile and birthweight ≥10th percentile. Of 84/111 infants with sufficient follow-up, 38/84 (45%) were classified as having possible inaccuracy of birth HC measurement, 19/84 (23%) had HC ≥3rd percentile on follow-up without meeting criteria for possible inaccuracy, and 27/84 (32%) had continued HC <3rd percentile. After excluding possible inaccuracies, the proportion of infants with Zika-associated birth defects including microcephaly decreased from 5.2% to 4.6%.

CONCLUSIONS

About one-third of infants in USZPIR with Zika-associated birth defects had only microcephaly, but indications of possible measurement inaccuracy were common. Implementation of this schema in longitudinal studies can reduce misclassification of microcephaly.

Autosomal Recessive Primary Microcephaly: Not Just a Small Brain

Microcephaly or reduced head circumference results from a multitude of abnormal developmental processes affecting brain growth and/or leading to brain atrophy. Autosomal recessive primary microcephaly (MCPH) is the prototype of isolated primary (congenital) microcephaly, affecting predominantly the cerebral cortex. For MCPH, an accelerating number of mutated genes emerge annually, and they are involved in crucial steps of neurogenesis. In this review article, we provide a deeper look into the microcephalic MCPH brain. We explore cytoarchitecture focusing on the cerebral cortex and discuss diverse processes occurring at the level of neural progenitors, early generated and mature neurons, and glial cells. We aim to thereby give an overview of current knowledge in MCPH phenotype and normal brain growth.

Population-based surveillance of severe microcephaly and congenital Zika syndrome in Canada

PURPOSE

To estimate the minimum incidence of congenital Zika syndrome (CZS) and severe microcephaly in Canada and describe key clinical, epidemiological, aetiological and outcome features of these conditions.

METHODS

Two separate national surveillance studies were conducted on CZS and severe microcephaly using the well-established Canadian Paediatric Surveillance Program from 2016 to 2019. Over 2700 paediatricians across Canada were surveyed monthly and asked to report demographic details, pregnancy and travel history, infant anthropometry, clinical features and laboratory findings of newly identified cases. Reports were reviewed to assign an underlying aetiology of severe microcephaly. Incidence rates were estimated using monthly live birth denominators.

RESULTS

Thirty-four infants met the case definition for severe microcephaly and <5 met the case definition for CZS. The associated minimum incidence rates were 4.5 per 100 000 live births for severe microcephaly and 0.1-0.5 per 100 000 live births for CZS. Of severe microcephaly cases, 53% were attributed to genetic causes, 15% to infectious or ischaemic causes and 32% to unknown causes. The median head circumference-for-age Z-score at birth was -3.2 (IQR -3.8 to -2.6), and catch-up growth was often not achieved. Common clinical features included intracranial abnormalities (n=23), dysmorphology (n=19) and developmental delays (n=14). Mothers of infants with non-genetic aetiologies travelled during pregnancy more often (10/16) than mothers of infants with genetic aetiologies (<5/18; p<0.01).

CONCLUSION

Severe microcephaly and CZS are both rare in Canada. Minimum incidence rates can be used as a baseline against which novel or re-emergent causes of severe microcephaly or CZS can be compared.

Microcephaly in Australian children, 2016-2018: national surveillance study

OBJECTIVE

To describe infants aged <12 months reported with microcephaly to the Australian Paediatric Surveillance Unit (APSU) following emergence of Zika virus infection internationally.

DESIGN, SETTING AND PATIENTS

National, active, monthly surveillance for microcephaly using the APSU. Microcephaly was defined as occipitofrontal circumference (OFC) of more than 2 SDs below the mean for age, gender and gestation.

MAIN OUTCOME MEASURES

Clinical spectrum, aetiology and birth prevalence of microcephaly reported by paediatricians.

RESULTS

Between June 2016 and July 2018, 106 notifications were received, with clinical details provided for 96 (91%). After excluding ineligible notifications, 70 cases were confirmed, giving an annual birth prevalence of 1.12 (95% CI 0.88 to 1.42) per 10 000 live births. Of the total number of cases, 47 (67%) had primary microcephaly (at birth); and 25 (36%) had severe microcephaly (OFC >3 SDs). Birth defects were reported in 42 (60%). Of 49 infants with developmental assessment details available, 25 (51%) had failed to reach all milestones. Vision impairment was reported in 14 (26%). The cause of microcephaly was unknown in 60%: 13 (19%) had been diagnosed with genetic disorders; 22 (39%) had anomalies on neuroimaging. No congenital or probable Zika infection was identified. Severe microcephaly was more often associated with hearing impairment than microcephaly of >2 SDs but ≤3 SDs below the mean (p<0.007). Indigenous children and children with socioeconomic advantage were over-represented among children with microcephaly.

CONCLUSION

Novel national data on microcephaly highlight the high proportion of idiopathic cases. This has implications for prevention and management and suggests the need for a standardised diagnostic approach and ongoing surveillance mechanism in Australia.

Causes of Microcephaly in the Zika Era in Argentina: A Retrospective Study

There are gaps in understanding the causes and consequences of microcephaly. This paper describes the epidemiological characteristics, clinical presentations, and etiologies of children presenting microcephaly during the Zika outbreak in Argentina. This observational retrospective study conducted in the pediatric hospital of Juan P. Garrahan reviewed the medical records of 40 children presenting microcephaly between March 2017 and November 2019. The majority (60%) were males and born full-term. At first evaluation, microcephaly was defined as congenital (31/40, 77%) and associated with other features (68%) such as seizures, developmental delay, non-progressive chronic encephalopathy, and West Syndrome. It was found manifestations restricted to central nervous system (55%), ocular (8/40, 20%), and acoustic (9/40, 23%) defects, and abnormal neuroimaging findings (31/39, 79%). Non-infectious diseases were the primary cause of isolated microcephaly (21/37, 57%), largely related to genetic diseases (13/21, 62%). Only 3 were children were diagnosed with Congenital Zika infection (3/16, 7.5%).

Prevalence and diagnostic accuracy of microcephaly in a pediatric cohort in Brazil: a retrospective cross-sectional study

OBJECTIVE

We sought to describe the prevalence of microcephaly and to compare the different cutoff points established by the Brazilian Ministry of Health at various times during a Zika virus epidemic. As a secondary aim, we investigated the possible etiology of the microcephaly.

METHOD

This retrospective study utilized newborn participants in the Zika Cohort Study Jundiaí. Newborns from the Zika Cohort Study Jundiaí with an accurate gestational age determination and complete anthropometric data were analyzed, and microcephaly was diagnosed according to the INTERGROWTH-21^st curve. At delivery, fluids were tested for specific antibodies and for viruses. Brain images were evaluated for microcephaly. Receiver Operating Characteristic curves were plotted to define the accuracy of different cutoff points for microcephaly diagnosis.

RESULTS

Of 462 eligible newborns, 19 (4.1%) were positive for microcephaly. Cutoff points corresponding to the curves of the World Health Organization yielded the best sensitivity and specificity. Three of the microcephaly cases (15.8%) were positive for Zika virus infections; nine (47.4%) had intrauterine growth restriction; one had intrauterine growth restriction and was exposed to Zika virus; three had a genetic syndrome (15.8%); and three had causes that had not been determined (15.8%).

CONCLUSIONS

Microcephaly prevalence was 4.1% in this study. Cutoff values determined by the World Health Organization had the highest sensitivity and specificity in relation to the standard IG curve. The main reason for microcephaly was intrauterine growth restriction. All possible causes of microcephaly must be investigated to allow the best development of an affected baby.

Causes of Phenotypic Variability and Disabilities after Prenatal Viral Infections

Prenatal viral infection can lead to a spectrum of neurodevelopmental disabilities or fetal demise. These can include microencephaly, global developmental delay, intellectual disability, refractory epilepsy, deafness, retinal defects, and cortical-visual impairment. Each of these clinical conditions can occur on a semi-quantitative to continuous spectrum, from mild to severe disease, and often as a collective of phenotypes. Such serious outcomes result from viruses’ overlapping neuropathology and hosts’ common neuronal and gene regulatory response to infections. The etiology of variability in clinical outcomes is not yet clear, but it may be related to viral, host, vector, and/or environmental risk and protective factors that likely interact in multiple ways. In this perspective of the literature, we work toward understanding the causes of phenotypic variability after prenatal viral infections by highlighting key aspects of the viral lifecycle that can affect human disease, with special attention to the 2015 Zika pandemic. Therefore, this work offers important insights into how viral infections and environmental teratogens affect the prenatal brain, toward our ultimate goal of preventing neurodevelopmental disabilities.

Prevalence of congenital microcephaly and its risk factors in an area at risk of Zika outbreaks

Background

Prevalence of neonatal microcephaly in populations without Zika-epidemics is sparse. The study aimed to report baseline prevalence of congenital microcephaly and its relationship with prenatal factors in an area at risk of Zika outbreak.

Methods

This study included singletons born after 24 gestational weeks in 2017–2018 at four hospitals in Guangzhou, China. Microcephaly was defined as a head circumference at birth >3SD below the mean for sex and gestational age. Prevalence of microcephaly was estimated by binomial exact method. Multivariable logistic regression was used to examine the associations of microcephaly with prenatal factors. The population attributable fraction (PAF) for associated risk factors was calculated.

Results

Of 46,610 live births included, 154 (3.3, 95% CI 2.8–3.9 per 1000 live births) microcephalies were identified. Maternal hepatitis B virus carriers (HBV, OR 1.80, 95% CI 1.05–3.10) and primipara (OR 2.68, 95% CI 1.89–3.81) had higher risk of having a microcephalic baby. Higher prevalence of microcephaly was observed in women who had premature labor (OR 1.98, 95% CI 1.17–3.34) and had a baby with fetal growth restriction (OR 16.38, 95% CI 11.81–22.71). Four identified factors (HBV, primiparity, preterm labor, and fetal growth restriction) contributed to 66.4% of the risk of microcephaly.

Conclusions

The prevalence of microcephaly in Guangzhou was higher than expected. This study identified four prenatal risk factors that, together, contributed to two-thirds of the increased risk of microcephaly. This is the first reported association between maternal HBV carrier status and microcephaly.

Use of infectious disease surveillance reports to monitor the Zika virus epidemic in Latin America and the Caribbean from 2015 to 2017: strengths and deficiencies

OBJECTIVES

To summarise the occurrence of congenital Zika syndrome (CZS) in Latin America and the Caribbean from 2015 to 2017 using two outcome measures derived from infectious disease surveillance reports and to assess the completeness of these reports.

DESIGN

Surveillance study.

SETTING

Pan American Health Organization (PAHO)/WHO epidemiology reports on confirmed and suspected Zika virus infection and cases of CZS.

PARTICIPANTS

Populations of 47 countries in the South and Central Americas, Mexico and the Caribbean.

PRIMARY AND SECONDARY OUTCOME MEASURES

The number of CZS cases per 1000 births (using 2016-2017 births as a denominator) and the number of CZS cases per 1000 births in women with Zika virus infection during pregnancy.

RESULTS

By 4 January 2018, 548623 suspected and 239063 confirmed Zika virus infections had been reported to PAHO/WHO from 47 countries. In 25 countries, over 80% of infections were reported as suspected. There were 3617 confirmed CZS cases in 25 countries; 2952 (82%) had occurred in Brazil. The number of CZS cases per 1000 births varied considerably with Brazil and several Caribbean island communities (Puerto Rico, St Martin, Martinique, Guadeloupe and Grenada) having the highest CZS prevalence above 0.5 per 1000 births. Analysing the number of CZS cases per 1000 births in women infected with Zika virus during their pregnancy highlighted the inaccuracies of the data, with Venezuela likely to have had severe under-reporting of CZS.

CONCLUSIONS

Expressing data on CZS in relation to total births, rather than as absolute numbers, better illustrates the burden of disease, providing that under-reporting of CZS is not too severe. Data on infections in pregnant women enable potential under-reporting of CZS to be identified. Both measures are recommended for future PAHO/WHO publications. Evidence of severe under-reporting of Zika virus infections and CZS makes interpretation of the data and comparisons between countries challenging.

Microcephaly epidemic in Brazil: An earlier chapter

OBJECTIVE

Identify risk factors for microcephaly and evaluate historical trends of microcephaly and arboviruses to recognize patterns and anomalies that indicate the beginning of the microcephaly epidemic associated with Zika infection.

METHODS

The head circumferences of 62,298 newborns was analyzed to identify cases of microcephaly between 2014 and 2017. We compared the groups of newborns with normal head circumferences and those with microcephaly to identify risk factors. A time series with the incidences of microcephaly was analyzed to assess the appearance of anomalous values in order to identify the beginning of the microcephaly epidemic. Data on the incidence of dengue fever was used to develop a control chart, aiming to identify changes in incidence and seasonality that could suggest the circulation of a new arbovirus.

FINDINGS

Premature newborns, children of mothers under 20 years of age and those born in 2014 and 2015 had a higher risk of microcephaly. Three quarters with anomalous incidences of microcephaly were identified, the first in 2014 and the others in 2015. The dengue fever epidemic curve in 2013 shows persistence of high incidences in atypical periods, suggesting the entry of a new virus in the 3rd and 4th quarters.

CONCLUSIONS

These findings represent epidemiological evidence of the existence of cases of Zika virus between the 2nd quarter of 2013 and the beginning of 2014. The results add new elements to understanding the Zika virus epidemic in the Americas.

Evaluation of a health information exchange system for microcephaly case-finding - New York City, 2013-2015

Background

Birth defects surveillance in the United States is conducted principally by review of routine but lagged reporting to statewide congenital malformations registries of diagnoses by hospitals or other health care providers, a process that is not designed to rapidly detect changes in prevalence. Health information exchange (HIE) systems are well suited for rapid surveillance, but information is limited about their effectiveness at detecting birth defects. We evaluated HIE data to detect microcephaly diagnosed at birth during January 1, 2013–December 31, 2015 before known introduction of Zika virus in North America.

Methods

Data from an HIE system were queried for microcephaly diagnostic codes on day of birth or during the first two days after birth at three Bronx hospitals for births to New York City resident mothers. Suspected cases identified by HIE data were compared with microcephaly cases that had been identified through direct inquiry of hospital records and confirmed by chart abstraction in a previous study of the same cohort.

Results

Of 16,910 live births, 43 suspected microcephaly cases were identified through an HIE system compared to 67 confirmed cases that had been identified as part of the prior study. A total of 39 confirmed cases were found by both studies (sensitivity = 58.21%, 95% CI: 45.52–70.15%; positive predictive value = 90.70%, 95% CI: 77.86–97.41%; negative predictive value = 99.83%, 95% CI: 99.76–99.89% for HIE data).

Conclusion

Despite limitations, HIE systems could be used for rapid newborn microcephaly surveillance, especially in the many jurisdictions where more labor-intensive approaches are not feasible. Future work is needed to improve electronic medical record documentation quality to improve sensitivity and reduce misclassification.

Spatiotemporal Analysis of the Population Risk of Congenital Microcephaly in Pernambuco State, Brazil

Since an outbreak in Brazil, which started in 2015, Zika has been recognized as an important cause of microcephaly. The highest burden of this outbreak was in northeast Brazil, including the state of Pernambuco. The prevalence of congenital microcephaly in Pernambuco state was estimated from the RESP (Registro de Eventos em Saúde Pública) surveillance system, from August 2015 to August 2016 inclusive. The denominators were estimated at the municipality level from official demographic data. Microcephaly was defined as a neonatal head circumference below the 3rd percentile of the Intergrowth standards. Smoothed maps of the prevalence of microcephaly were obtained from a Bayesian model which was conditional autoregressive (CAR) in space, and first order autoregressive in time. A total of 742 cases were identified. Additionally, high and early occurrences were identified in the Recife Metropolitan Region, on the coast, and in a north–south band about 300 km inland. Over a substantial part of the state, the overall prevalence, aggregating over the study period, was above 0.5%. The reasons for the high occurrence in the inland area remain unclear.

Association of maternal antiretroviral use with microcephaly in children who are HIV-exposed but uninfected (SMARTT): a prospective cohort study

BACKGROUND

Perinatal HIV transmission has substantially decreased with combination antiretroviral regimens, but complications in children who are HIV-exposed but uninfected, such as microcephaly, warrant ongoing surveillance. We aimed to evaluate whether individual in utero antiretroviral exposures were associated with increased risk of microcephaly based on long-term follow-up of infants and children who are HIV-exposed but uninfected.

METHODS

We evaluated children aged younger than 18 years who were HIV-exposed but uninfected with at least one head circumference measurement while enrolled in the Surveillance Monitoring for ART Toxicities (SMARTT) study at 22 clinical sites in the USA, including Puerto Rico. This prospective cohort study was done by the Pediatric HIV/AIDS Cohort Study network. Microcephaly was defined as having a head circumference Z score <-2 according to the 2000 US Centers for Disease Control and Prevention growth charts for children 6-36 months old and according to Nellhaus standards (head circumference <2nd percentile) after 36 months (SMARTT criteria); an alternate definition for microcephaly was based on applying Nellhaus standards across all ages (Nellhaus criteria). Modified Poisson regression models were fit to obtain relative risks (RRs) for associations between in utero antiretroviral exposure and microcephaly status, adjusted for potential confounders. Neurodevelopmental functioning was compared in children who are HIV-exposed but uninfected with or without microcephaly.

FINDINGS

Between March 21, 2007, and Aug 1, 2017, 3055 participants enrolled in SMARTT had at least one head circumference measurement. The cumulative incidence of microcephaly over a median of 5·1 years of follow-up (IQR 3·0-7·2) was 159 (5·2%, 95% CI 4·4-6·1) by Nellhaus criteria and 70 (2·3%, 1·8-2·9) by SMARTT criteria. In adjusted models, in utero exposure to efavirenz (4·7% exposed) was associated with increased risk of microcephaly by both Nellhaus standards (adjusted RR 2·02, 95% CI 1·16-3·51) and SMARTT criteria (2·56, 1·22-5·37). These associations were more pronounced in children exposed to combination regimens of efavirenz that included zidovudine plus lamivudine than those including tenofovir plus emtricitabine. Protective associations were observed for darunavir exposure (adjusted RR 0·50, 95% CI 0·24-1·00). Children who are HIV-exposed but uninfected with microcephaly had lower mean scores on neurodevelopmental assessments at age 1 and 5 years and a higher prevalence of neurodevelopmental impairment than those without microcephaly.

INTERPRETATION

These findings support consideration of alternatives to efavirenz as part of first-line antiretroviral therapy for pregnant women.

FUNDING

Eunice Kennedy Shriver National Institute of Child Health and Human Development.

Congenital microcephaly hospitalizations in California infants: 1999-2013

INTRODUCTION

Population-level changes in microcephaly incidence risk (IR) could signal circulation of neurotropic pathogens or potential emerging teratogen exposure.

METHODS

In this retrospective population cohort study, we estimated the IR of hospitalizations with a microcephaly ICD-9-CM discharge diagnosis code among infants ≤1 year over a 15-year period (1999-2013) using the Electronic Health Record (EHR) database from all hospital discharges in California from the Office of Statewide Hospital Planning and Development (OSHPD) database. We calculated the overall and yearly IRs per 10,000 live births (LBs) and per 10,000 hospitalizations in infants ≤1 year, and explored the impact in the IR estimates when children with microcephaly associated comorbidities were excluded or not.

RESULTS

Among 8,860,153 hospital discharges of infants ≤1 year in the OSHPD database over this 15 year period, we identified 6,004 hospitalizations with a microcephaly discharge diagnosis code; 3,526 of those were in neonates ≤30 days. The IR of microcephaly hospitalizations for infants ≤1 year was 7.70/10,000 LB (for neonates it was 4.52/10,000 LB) and 6.78 per 10,000 hospitalizations ≤1 year. There was large heterogeneity in the yearly microcephaly IRs (I² = 66.6%).

DISCUSSION

EHR collected data could be used as a complementary approach to track epidemiologic changes in microcephaly IRs. However, standardization in the use of microcephaly discharge diagnosis code and harmonization in the types of additional comorbidities to be excluded across analyses is mandatory to allow for prompt identification of true changes in microcephaly rates over time.

Prevalence and causes of congenital microcephaly in the absence of a Zika virus outbreak in southern Brazil

OBJECTIVE

The aim of this study was to identify the causes of congenital microcephaly in Rio Grande do Sul, a state in southern Brazil, where no ZIKV outbreak was detected, from December 2015 to December 2016, which was the period when ZIKV infection was at its peak in northeast Brazil.

METHODS

This was a cross-sectional study where all notifications of congenital microcephaly in the state of Rio Grande do Sul were included for analysis. Evaluation of cases followed the guidelines of the Brazilian Ministry of Health. Dysmorphological and neurological evaluations were performed by a specialized team, and genetic tests and neuroimaging were performed when clinically indicated. STORCH infections were diagnosed using standard tests. ZIKV infection was diagnosed through maternal serum RT-PCR and/or neuroimaging associated with clinical/epidemiological criteria.

RESULTS

From 153744 registered live births in the study period, 148 cases were notified, but 90 (60.8%) of those were later excluded as "non-confirmed" microcephaly. In the 58 confirmed cases of microcephaly (prevalence = 3.8/10000 live births), congenital infections (syphilis, toxoplasmosis, cytomegalovirus, and ZIKV) constituted the predominant etiology (50.0%), followed by isolated CNS (15.5%), and genetic syndromes (10.3%). Congenital ZIKV syndrome (CZS) with typical phenotype was diagnosed in three cases (5.2% of all confirmed microcephaly cases or 10.4% of all congenital infections).

CONCLUSION

In Rio Grande do Sul, where no outbreak of ZIKV infection was recorded, congenital infections were the leading cause of congenital microcephaly, and the attributable risk for CZS in the etiology of microcephaly was 5.2%.

Misclassification in defining and diagnosing microcephaly

BACKGROUND

Several health agencies define microcephaly for surveillance purposes using a single criterion, a percentile or Z-score cut-off for newborn head circumference. This definition, however, conflicts with the reported prevalence of microcephaly even in populations with endemic Zika virus.

OBJECTIVE

We explored possible reasons for this conflict, hypothesising that the definition of microcephaly used in some studies may be incompletely described, lacking the additional clinical criteria that clinicians use to make a formal diagnosis. We also explored the potential for misclassification that can result from differences in these definitions, especially when applying a percentile cut-off definition in the presence of the much lower observed prevalence estimates that we believe to be valid.

METHODS

We conducted simulations under a theoretical bimodal distribution of head circumference. For different definitions of microcephaly, we calculated the sensitivity and specificity using varying cut-offs of head circumference. We then calculated and plotted the positive predictive value for each of these definitions by prevalence of microcephaly.

RESULTS

Simple simulations suggest that if the true prevalence of microcephaly is approximately what is reported in peer-reviewed literature, then relying on cut-off-based definitions may lead to very poor positive predictive value under realistic conditions.

CONCLUSIONS

While a simple head circumference criterion may be used in practice as a screening or surveillance tool, the definition lacks clarification as to what constitutes true pathological microcephaly and may lead to confusion about the true prevalence of microcephaly in Zika-endemic areas, as well as bias in aetiologic studies.

First 12 Months of Life for Infants in New York City, New York, With Possible Congenital Zika Virus Exposure

BACKGROUND

Our goal was to characterize the epidemiology and clinical significance of congenital Zika virus (ZIKV) exposure by prospectively following a cohort of infants with possible congenital exposure through their first year of life.

METHODS

We included infants born in New York City between 2016 and 2017 who had or were born to a woman who had laboratory evidence of ZIKV infection during pregnancy. We conducted provider/patient interviews and reviewed medical records to collect information about the pregnant women and, for infants, clinical and neurodevelopmental status at birth and 2, 6, and 12 months of age.

RESULTS

Of the 404 infants who met inclusion criteria, most (385 [95.3%]) appeared well, whereas 19 (4.7%) had a possible ZIKV-associated birth defect. Seven had congenital ZIKV syndrome, and 12 were microcephalic without other abnormalities. Although infants with congenital ZIKV syndrome manifested clinical and neurodevelopmental sequelae during their first year of life, all 12 infants with isolated microcephaly were normocephalic and appeared well by 2 months of age. Laboratory evidence of ZIKV was detected for 22 of the infants, including 7 (31.8%) with a birth defect. Among 148 infants without a birth defect and negative/no laboratory results on ZIKV testing, and for whom information was available at 1 year, 4 presented with a developmental delay.

CONCLUSIONS

Among infants with possible congenital ZIKV exposure, a small proportion had possible ZIKV-associated findings at birth or at follow-up, or laboratory evidence of ZIKV. Identifying and monitoring infants with possible ZIKV exposure requires extensive efforts by providers and public health departments. Longitudinal studies using standardized clinical and developmental assessments are needed for infants after possible congenital ZIKV exposure.

Temporal trends in diagnoses of congenital microcephaly, Texas Hospital Discharge Diagnoses, 2000-2015

OBJECTIVE

Assess temporal trends in congenital microcephaly.

METHODS

We used Texas inpatient discharge diagnoses between 2000 and 2015, restricting to newborns. Between 2000 and 2003, the maximum number of fields for recording diagnostic codes was eight, and between 2004 and 2015 it was 24. Microcephaly was classified into four subgroups based on co-occurring diagnoses: A (Known Causes), B (Other Birth Defects), C (Preterm Birth or Fetal Growth Restriction) and D (Isolated Cases).

RESULTS

We identified 2,301 cases of microcephaly or 4.0 cases per 10,000 live births. There was an increase in the prevalence of microcephaly in 2012-2015 compared with 2000-2003, odds ratio = 1.85 (95% CI 1.64-2.10) Significant temporal increases in microcephaly were observed within each of the four microcephaly subgroups and significant temporal increases were also observed for eight other neonatal diagnoses during the same time period. When we restricted our analysis to cases with microcephaly identified using only the eight diagnostic codes available throughout the entire study period, the temporal trend for microcephaly was diminished or absent.

CONCLUSIONS

It remains uncertain whether the observed increases in microcephaly and other neonatal diagnoses are real or an artifact of the change in the number of fields. However, since it is unlikely that there would be a simultaneous increase in microcephaly and eight other neonatal diagnoses, it is likely that some or all of the temporal increases in neonatal diagnoses are artifactual.

Small head circumference at birth: an 8-year retrospective cohort study in China

OBJECTIVE

Head circumference is considered a reliable assessment of the volume of the underlying brain. We sought to identify risk factors (maternal factors or antenatal antecedents) for microcephaly and to assess the effects of microcephaly on neonatal outcomes.

DESIGN

Retrospective cohort study.

SETTING

Data for all births in 2009-2017 were obtained from the Guangzhou Maternal-Fetal Care Database.

PARTICIPANTS

All singleton liveborn infants between 33 and 42 weeks' gestation (n=45 663) were categorised using the Intergrowth-21st standard for microcephaly.

MAIN OUTCOME MEASURES

Prevalence of mild, absolute and relative microcephaly at birth. We estimated associations of (1) maternal characteristics including Cantonese origin, parity, exposure to teratogens, TORCH infections (ie, Toxoplasma gondii, rubella virus, cytomegalovirus, herpes simplex virus), in vitro fertilisation conception, pre-eclampsia and maternal congenital anomalies with risk of each category of microcephaly, and (2) microcephaly with risk of in-hospital mortality and severe morbidity.

RESULTS

A total of 2709 infants had a head circumference z-score >2 SD, resulting in an overall prevalence of microcephaly of 59.3 per 1000 infants, consisting of mild (54.1 per 1000), absolute (2.8 per 1000) and relative microcephaly (2.4 per 1000). In multiple logistic regression, absolute microcephaly was associated with in utero exposure to teratogens (OR 4.2, 95% CI 2.0 to 8.8) and TORCH agents (OR 3.2, 95% CI 1.1 to 9.5). Mild microcephaly was associated with Cantonese descent (OR) 1.5, 95% CI 1.3 to 1.7) and primiparity (OR 1.7, 95% CI 1.5 to 2.0). Absolute microcephaly was associated with a significantly higher odds of neonatal seizure (OR 8.7, 95% CI 1.1 to 69.1). Mild microcephaly was not associated with adverse neonatal outcomes overall.

CONCLUSIONS

Cantonese origin, exposure to teratogens, pre-eclampsia and TORCH infection may be risk factors for microcephaly. The high prevalence of relative microcephaly and associated poor outcomes suggests that high-risk women merit closer clinical management and follow-up to maximise fetal head development during pregnancy.

Studying the effects of emerging infections on the fetus: Experience with West Nile and Zika viruses

Emerging infections have the potential to produce adverse effects on the pregnant woman or her fetus; however, studying these effects is often challenging. We review our experiences with investigating the prenatal effects of two mosquito‐borne infections that emerged in the past 2 decades, West Nile virus (WNV) and Zika virus. Concerns regarding teratogenicity were raised about both viruses; Zika virus has been confirmed to be teratogenic, while WNV appears not to increase the risk for adverse outcomes, although teratogenicity has not been excluded. Study designs used to examine the effects of both viruses include case reports and series, pregnancy registries, and cohort studies. Case–control studies and birth defects surveillance systems are being used to study the effects during pregnancy of Zika virus, but not the effects of WNV, because a specific phenotype was observed among infants with congenital Zika infection, but not among infants with congenital WNV infection. Experimental data that demonstrated that Zika virus was neurotropic have also been useful because they provided biologic plausibility for Zika virus's teratogenic effects: these findings were consistent with observations in congenitally infected infants. Challenges encountered with studies to evaluate the effects of these infections include the broad range of possible adverse outcomes, the inability to include all infected pregnant women in studies because many infections are asymptomatic, and the difficulty with interpretation of diagnostic testing of infants (WNV and Zika) and pregnant women (Zika). This review might be helpful to guide future studies of the effects of emerging infections during pregnancy. Birth Defects Research 109:363–371, 2017. © 2017 Wiley Periodicals, Inc.

An assessment of public health surveillance of Zika virus infection and potentially associated outcomes in Latin America

BACKGROUND

We evaluated whether outbreaks of Zika virus (ZIKV) infection, newborn microcephaly, and Guillain-Barré syndrome (GBS) in Latin America may be detected through current surveillance systems, and how cases detected through surveillance may increase health care burden.

METHODS

We estimated the sensitivity and specificity of surveillance case definitions using published data. We assumed a 10% ZIKV infection risk during a non-outbreak period and hypothetical increases in risk during an outbreak period. We used sensitivity and specificity estimates to correct for non-differential misclassification, and calculated a misclassification-corrected relative risk comparing both periods. To identify the smallest hypothetical increase in risk resulting in a detectable outbreak we compared the misclassification-corrected relative risk to the relative risk corresponding to the upper limit of the endemic channel (mean + 2 SD). We also estimated the proportion of false positive cases detected during the outbreak. We followed the same approach for microcephaly and GBS, but assumed the risk of ZIKV infection doubled during the outbreak, and ZIKV infection increased the risk of both diseases.

RESULTS

ZIKV infection outbreaks were not detectable through non-serological surveillance. Outbreaks were detectable through serologic surveillance if infection risk increased by at least 10%, but more than 50% of all cases were false positive. Outbreaks of severe microcephaly were detected if ZIKV infection increased prevalence of this condition by at least 24.0 times. When ZIKV infection did not increase the prevalence of severe microcephaly, 34.7 to 82.5% of all cases were false positive, depending on diagnostic accuracy. GBS outbreaks were detected if ZIKV infection increased the GBS risk by at least seven times. For optimal GBS diagnosis accuracy, the proportion of false positive cases ranged from 29 to 54% and from 45 to 56% depending on the incidence of GBS mimics.

CONCLUSIONS

Current surveillance systems have a low probability of detecting outbreaks of ZIKV infection, severe microcephaly, and GBS, and could result in significant increases in health care burden, due to the detection of large numbers of false positive cases. In view of these limitations, Latin American countries should consider alternative options for surveillance.

Establishing Mouse Models for Zika Virus-induced Neurological Disorders Using Intracerebral Injection Strategies: Embryonic, Neonatal, and Adult

The Zika virus (ZIKV) is a flavivirus currently endemic in North, Central, and South America. It is now established that the ZIKV can cause microcephaly and additional brain abnormalities. However, the mechanism underlying the pathogenesis of ZIKV in the developing brain remains unclear. Intracerebral surgical methods are frequently used in neuroscience research to address questions about both normal and abnormal brain development and brain function. This protocol utilizes classical surgical techniques and describes methods that allow one to model ZIKV-associated human neurological disease in the mouse nervous system. While direct brain inoculation does not model the normal mode of virus transmission, the method allows investigators to ask targeted questions concerning the consequence after ZIKV infection of the developing brain. This protocol describes embryonic, neonatal, and adult stages of intraventricular inoculation of ZIKV. Once mastered, this method can become a straightforward and reproducible technique that only takes a few hours to perform.

Prevalence and Risk Factors for Microcephaly at Birth in Brazil in 2010

OBJECTIVES

To estimate the baseline prevalence and risk factors for microcephaly at birth before the Zika virus epidemic in 2 Brazilian cities.

METHODS

We used population-based data from the Brazilian Ribeirão Preto (RP) and São Luís (SL) birth cohort studies of 2010 that included hospital deliveries by resident mothers. The final sample was 7376 live births in RP and 4220 in SL. Gestational age was based on the date of the mother's last normal menstrual period or obstetric ultrasonography, if available. Microcephaly at birth was classified according to the criteria of the International Fetal and Newborn Growth Consortium for the 21st Century and the Brazilian Ministry of Health. Risk factors for microcephaly, proportionate and disproportionate microcephaly, and severe microcephaly were estimated in a hierarchized logistic regression model.

RESULTS

According to the International Fetal and Newborn Growth Consortium for the 21st Century definition, the prevalence of microcephaly (>2 SDs below the mean for gestational age and sex) was higher in SL (3.5%) than in RP (2.5%). The prevalence of severe microcephaly (>3 SDs below the mean) was higher in SL (0.7%) than in RP (0.5%). Low maternal schooling, living in consensual union or without a companion, maternal smoking during pregnancy, primiparity, vaginal delivery, and intrauterine growth restriction were consistently associated with microcephaly. The number of cases of microcephaly is grossly underestimated, with an underreporting rate of ∼90%.

CONCLUSIONS

The prevalence of severe microcephaly was much higher than expected in both cities. Our findings suggest that microcephaly was endemic in both municipalities before the circulation of the Zika virus.

Fever in pregnancy and offspring head circumference

PURPOSE

To examine whether maternal fever during pregnancy is associated with reduced head circumference and risk of microcephaly at birth.

METHODS

A prospective study of 86,980 live-born singletons within the Danish National Birth Cohort was carried out. Self-reported maternal fever exposure was ascertained in two interviews during pregnancy and information on head circumference at birth was extracted from the Danish Medical Birth Registry.

RESULTS

Fever in pregnancy was reported by 27% of the mothers, and we identified 3370 cases of microcephaly (head circumference less than or equal to third percentile for sex and gestational age) and 1140 cases of severe microcephaly (head circumference less than or equal to first percentile for sex and gestational age). In this study, maternal fever exposure was not associated with reduced head circumference (adjusted β = 0.03, 95% confidence intervals [CI]: 0.01-0.05), increased risk of microcephaly (odds ratio: 0.95, 95% CI: 0.88-1.03) nor severe microcephaly (odds ratio: 1.01, 95% CI: 0.88-1.15) in the offspring. These findings were consistent for increasing numbers of fever episodes, for increasing fever severity, and for exposure in both early pregnancy and midpregnancy.

CONCLUSIONS

In this most comprehensive study to date, we found no indication that maternal fever in pregnancy is associated with small head size in the offspring.

Maternal Zika virus infection and newborn microcephaly-an analysis of the epidemiological evidence

PURPOSE

To evaluate whether existing data and evidence support a causal link between maternal Zika virus (ZIKV) infection and newborn microcephaly.

METHODS

I quantified and compared the prevalence of all and severe microcephaly in Brazil, during and before 2015-2016, to assess whether an outbreak has occurred, used time series analysis to evaluate if the presumed outbreak was linked to a previous outbreak of ZIKV infections, and quantitatively synthesized published data from observational studies testing this association.

RESULTS

The prevalences of microcephaly in 2015-2016 were similar or lower than background levels (prevalence ratio [PR] for all microcephaly: 0.19; 95% confidence intervals [CI]: 0.17, 0.20). Changes in the number of cases of ZIKV infections at times matching 11-18 weeks of pregnancy were not followed by changes in the number of microcephaly cases (PR for infection at 12 weeks: 1.02; 95% CI: 0.99, 1.05). In observational studies, the prevalence of microcephaly was not significantly increased in newborns of Zika-infected mothers (average PR: 1.30; 95% CI: 0.84, 2.02).

CONCLUSIONS

Existing evidence is insufficient to claim maternal ZIKV infection causes microcephaly. Although a public health response seems sensible, it should be consistent with existing knowledge and consider risks, potential benefits and harm, and competing priorities.

A Possible Link Between Pyriproxyfen and Microcephaly

The Zika virus has been the primary suspect in the large increase in incidence of microcephaly in 2015-6 in Brazil. While evidence for Zika being the cause of some of the cases is strong, its role as the primary cause of the large number of cases in Brazil has not been confirmed. Recently, the disparity between the incidences in different geographic locations has led to questions about the virus's role. Here we consider the alternative possibility that the use of the insecticide pyriproxyfen for control of mosquito populations in Brazilian drinking water is the primary cause. Pyriproxifen is a juvenile hormone analog which has been shown to correspond in mammals to a number of fat soluble regulatory molecules including retinoic acid, a metabolite of vitamin A, with which it has cross-reactivity and whose application during development has been shown to cause microcephaly. Methoprene, another juvenile hormone analog that was approved as an insecticide based upon tests performed in the 1970s, has metabolites that bind to the mammalian retinoid X receptor, and has been shown to cause developmental disorders in mammals. Isotretinoin is another example of a retinoid causing microcephaly in human babies via maternal exposure and activation of the retinoid X receptor in developing fetuses. Moreover, tests of pyriproxyfen by the manufacturer, Sumitomo, widely quoted as giving no evidence for developmental toxicity, actually found some evidence for such an effect, including low brain mass and arhinencephaly-incomplete formation of the anterior cerebral hemispheres-in exposed rat pups. Finally, the pyriproxyfen use in Brazil is unprecedented-it has never before been applied to a water supply on such a scale. Claims that it is not being used in Recife, the epicenter of microcephaly cases, do not distinguish the metropolitan area of Recife, where it is widely used, and the municipality, and have not been adequately confirmed. Given this combination of information about molecular mechanisms and toxicological evidence, we strongly recommend that the use of pyriproxyfen in Brazil be suspended until the potential causal link to microcephaly is investigated further.

Pre-Zika descriptive epidemiology of microcephaly in Texas, 2008-2012

BACKGROUND

There are limited population-based studies on microcephaly. We characterized the epidemiology of microcephaly in Texas during a 5-year period (2008-2012), prior to the Zika epidemic in the Western hemisphere (2015). The associations of suspected risk factors were compared across four clearly defined case groups.

METHODS

Data from the Texas Birth Defects Registry were used to calculate the prevalence of congenital microcephaly and crude and adjusted prevalence ratios using Poisson regression. Twelve maternal and infant factors were assessed across case groups, which included total (explained + unexplained), explained (e.g., syndromic), unexplained, and severe unexplained microcephaly (head circumference <3^rd percentile).

RESULTS

The birth prevalence for total and total severe microcephaly were 14.7 and 4.8 per 10,000 livebirths, respectively. For explained and unexplained cases, significantly elevated risks were noted for mothers who were older (35+), less educated (≤12 years), diabetic (pre-pregnancy or gestational), or had a preterm delivery. Unlike explained cases, however, mothers who were non-White or smoked had an increased risk for unexplained microcephaly. Furthermore, young maternal age (<20), multiparity, and higher BMI reduced the risk for unexplained microcephaly. For severe unexplained cases, the risk profile was similar to that for all unexplained cases-with the exception of null associations noted for diabetes and birth year.

CONCLUSIONS

We found that risk patterns for microcephaly varied across case groupings. Risk factors included maternal race/ethnicity, age, and smoking during pregnancy. Among severe unexplained cases, notable positive associations were seen among mothers who were non-Hispanic Black or less educated, while inverse associations were noted for obesity.

Prevalence and clinical profile of microcephaly in South America pre-Zika, 2005-14: prevalence and case-control study

Objective To describe the prevalence and clinical spectrum of microcephaly in South America for the period 2005-14, before the start of the Zika epidemic in 2015, as a baseline for future surveillance as the Zika epidemic spreads and as other infectious causes may emerge in future.Design Prevalence and case-control study.Data sources ECLAMC (Latin American Collaborative Study of Congenital Malformations) database derived from 107 hospitals in 10 South American countries, 2005 to 2014. Data on microcephaly cases, four non-malformed controls per case, and all hospital births (all births for hospital based prevalence, resident within municipality for population based prevalence). For 2010-14, head circumference data were available and compared with Intergrowth charts.Results 552 microcephaly cases were registered, giving a hospital based prevalence of 4.4 (95% confidence interval 4.1 to 4.9) per 10 000 births and a population based prevalence of 3.0 (2.7 to 3.4) per 10 000. Prevalence varied significantly between countries and between regions and hospitals within countries. Thirty two per cent (n=175) of cases were prenatally diagnosed; 29% (n=159) were perinatal deaths. Twenty three per cent (n=128) were associated with a diagnosed genetic syndrome, 34% (n=189) polymalformed without a syndrome diagnosis, 12% (n=65) with associated neural malformations, and 26% (n=145) microcephaly only. In addition, 3.8% (n=21) had a STORCH (syphilis, toxoplasmosis, other including HIV, rubella, cytomegalovirus, and herpes simplex) infection diagnosis and 2.0% (n=11) had consanguineous parents. Head circumference measurements available for 184/235 cases in 2010-14 showed 45% (n=82) more than 3 SD below the mean, 24% (n=44) between 3 SD and 2 SD below the mean, and 32% (n=58) larger than -2 SD.Conclusion Extrapolated to the nearly 7 million annual births in South America, an estimated 2000-2500 microcephaly cases were diagnosed among births each year before the Zika epidemic began in 2015. Clinicians are using more than simple metrics to make microcephaly diagnoses. Endemic infections are important enduring causes of microcephaly.

Risk of bias and confounding of observational studies of Zika virus infection: A scoping review of research protocols

INTRODUCTION

Given the severity and impact of the current Zika virus (ZIKV) outbreak in the Americas, numerous countries have rushed to develop research studies to assess ZIKV and its potential health consequences. In an effort to ensure that studies are comprehensive, both internally and externally valid, and with reliable results, the World Health Organization, the Pan American Health Organization, Institut Pasteur, the networks of Fiocruz, the Consortia for the Standardization of Influenza Seroepidemiology (CONSISE) and the International Severe Acute Respiratory and Emerging Infection Consortium (ISARIC) have generated six standardized clinical and epidemiological research protocols and questionnaires to address key public health questions on ZIKV.

METHODS

We conducted a systematic search of ongoing study protocols related to ZIKV research. We analyzed the content of protocols of 32 cohort studies and 13 case control studies for systematic bias that could produce erroneous results. Additionally we aimed to characterize the risks of bias and confounding in observational studies related to ZIKV and to propose ways to minimize them, including the use of six newly standardized research protocols.

RESULTS

Observational studies of ZIKV face an array of challenges, including measurement of exposure and outcomes (microcephaly and Guillain-Barré Syndrome). Potential confounders need to be measured where known and controlled for in the analysis. Selection bias due to non-random selection is a significant issue, particularly in the case-control design, and losses to follow-up is equally important for the cohort design.

CONCLUSION

Observational research seeking to answer key questions on the ZIKV should consider these restrictions and take precautions to minimize bias in an effort to provide reliable and valid results. Utilization of the standardized research protocols developed by the WHO, PAHO, Institut Pasteur, and CONSISE will harmonize the key methodological aspects of each study design to minimize bias at different stages of the study. Biases need to be considered by researchers implementing the standardized protocols as well as by users of observational epidemiological studies of ZIKV.