Structural anomalies resulting from vascular disruption

Prevalence of congenital anomalies and prenatal diagnosis by birth institution (public vs. non-public): indicators of inequality in access to elective termination of pregnancy for fetal anomalies

Congenital anomalies (CA) encompass all morphological or functional alterations originating prenatally and present at birth. The prenatal diagnosis of these anomalies can significantly impact the overall health of the pregnant individual and may influence her decision regarding the continuation of the pregnancy. In contexts where safe pregnancy termination is not guaranteed by the state, it can lead to unsafe procedures with severe consequences. In our research, we analyzed epidemiological information on CA to develop potential indicators of inequity in access to safe abortion prior to the legalization of legal termination of pregnancy in Argentina. We included cases from 13 public hospitals and 9 non-public subsector hospitals, from the period 2013-2020. Two groups of specific CA were selected: 1) CA capable of being prenatally diagnosed, and 2) CA related to vascular disruptive events. 10/18 of the selected CA capable of being prenatally diagnosed had a significantly higher prevalence in public hospitals (anencephaly, encephalocele, spina bifida, microcephaly, hydrocephalus, holoprosencephaly, hydranencephaly, diaphragmatic hernia, gastroschisis, bilateral renal agenesis). Non public hospitals had higher prenatal detection. Birth prevalence of CA related with vascular disruptive events (limb reduction, Moebius syndrome, amniotic band sequence) were significantly higher in public hospitals. These results suggest disparities in access to prenatal diagnosis and safe abortion based on socioeconomic status. There was a significant gap in access to prenatal diagnosis for CA and possibly to safe elective abortion depending on the type of institution (public vs. non-public).

Hypothesis: Central digit hypoplasia

Limb deficiencies are a common birth defect. A malformations surveillance program among many newborns, stillborn fetuses, and malformed fetuses in elective terminations can identify a sufficient number of infants with the same set of abnormalities to characterize a specific limb deficiency phenotype. The active malformations surveillance program was carried out among 289,365 births at Brigham and Women's Hospital in Boston over a 41-year period (1972-2012). The research assistants identified the affected infants and fetuses from reading the findings recorded in each newborn's medical record by the examining pediatricians and consultants and by the pathologists in autopsies. One hundred ninety-four newborn infants and fetuses were found to have a limb deficiency either as an isolated abnormality or as one of multiple malformations. We identified three phenotypes of limb deficiency. We present here the seventeen infants and fetuses with "central digit hypoplasia," a term we suggest for this phenotype: hypoplasia of the thumb and fifth finger with nubbins of soft tissue in place of fingers 2, 3, and 4 at the level of the metacarpal-phalangeal joint. Central digit hypoplasia is to be distinguished primarily from the terminal transverse limb defect that ends at the wrist. In symbrachydactyly, the middle and distal phalanges of the fingers and toes are hypoplastic. In addition, central digit hypoplasia should be distinguished from the amniotic band syndrome, the most common and incorrect diagnosis suggested by the pediatricians and the consultants in this survey. The affected infant and her/his parents benefit from more accurate and specific counseling.

Vasoactive exposures and risk of amniotic band syndrome and terminal transverse limb deficiencies

INTRODUCTION

Amniotic band syndrome (ABS) includes limb deficiencies accompanied by fibrous strands originating from the amniotic lining. Terminal transverse limb deficiencies (TTLD) appear to be similar but lack fibrous strands. Both are hypothesized to result from vascular disruption. For ABS, limb deficiencies are considered secondary to amnion rupture. We explored an alternative possibility-that TTLD is the primary defect and ABS is secondary.

METHODS

Using data from the National Birth Defects Prevention Study, we expanded on a previous study. We examined smoking, alcohol, and medications categorized by indicated vasoactivity as markers of vascular disruption. Logistic regression models with Firth's penalized likelihood were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs).

RESULTS

Use of bronchodilators and aspirin appeared to increase the risk of ABS, while decongestants and nonaspirin NSAIDs increased the risk of TTLD. The risk of ABS was markedly increased in cases reporting combinations of vasoactive exposures, particularly alcohol and aspirin (aOR 3.7, 95% CI 1.6, 7.8), and alcohol and bronchodilators (aOR 3.4, 95% CI 1.4, 7.5). Increased risk of TTLD due to combinations of vasoactive exposures was only observed for smoking and decongestants (aOR 2.3, 95% CI 1.4, 3.6).

CONCLUSIONS

Exposures associated with increased risk of ABS had no apparent association with TTLD, supporting previous evidence that these may be distinct phenotypes. ABS appears to be associated with combined exposures with vasodilation properties, such as alcohol and bronchodilators, while increased risk of TTLD may be associated with smoking and decongestants, both vasoconstrictive exposures.

Vertebrate embryos as tools for anti-angiogenic drug screening and function

The development of new angiogenic inhibitors highlights a need for robust screening assays that adequately capture the complexity of vessel formation, and allow for the quantitative evaluation of the teratogenicity of new anti-angiogenic agents. This review discusses the use of screening assays in vertebrate embryos, specifically focusing upon chicken and zebrafish embryos, for the detection of anti-angiogenic agents.

Identification of vascular disruptor compounds by analysis in zebrafish embryos and mouse embryonic endothelial cells

To identify vascular disruptor compounds (VDCs), this study utilized an in vivo zebrafish embryo vascular model in conjunction with a mouse endothelial cell model to screen a subset of the U.S. Environmental Protection Agency (EPA) ToxCast Phase I chemical inventory. In zebrafish, 161 compounds were screened and 34 were identified by visual inspection as VDCs, of which 28 were confirmed as VDCs by quantitative image analysis. Testing of the zebrafish VDCs for their capacity to inhibit endothelial tube formation in the murine yolk-sac-derived endothelial cell line C166 identified 22 compounds that both disrupted zebrafish vascular development and murine endothelial in vitro tubulogenesis. Putative molecular targets for the VDCs were predicted using EPA's Toxicological Prioritization Index tool and a VDC signature based on a proposed adverse outcome pathway for developmental vascular toxicity. In conclusion, our screening approach identified 22 novel VDCs, some of which were active at nanomolar concentrations.

Exposure to methylergonovine maleate as a cause of sirenomelia

BACKGROUND

Sirenomelia is a rare, but deadly condition characterized by fusion of the lower limbs, lower spinal column defects, severe malformations of the urogenital and lower gastrointestinal tract, and an aberrant abdominal umbilical artery.

METHODS

The two main hypotheses, not mutually exclusive, that have been advanced to explain the pathogenesis of sirenomelia are the blastogenetic theory and the vascular disruption theory.

RESULTS

We describe a case of sirenomelia, probably associated with the use of methylergonovine maleate, an ergot alkaloid, during the first weeks of pregnancy.

CONCLUSION

On the basis of the mechanisms of vascular disruption and early administration of methylergonovine maleate at a critical stage of organogenesis, we conclude that exposure to methylergonovine maleate could be the cause of the development of sirenomelia. Birth Defects Research (Part A) 106:643-647, 2016. © 2016 Wiley Periodicals, Inc.

Use of selective serotonin-reuptake inhibitors during pregnancy and the risk of clubfoot

BACKGROUND

Selective serotonin-reuptake inhibitors (SSRIs) are the most commonly prescribed antidepressants. Previous studies have suggested that SSRIs may increase the risk of birth defects, including clubfoot. Using data from a population-based case-control study, we evaluated whether SSRI use increased the risk of clubfoot.

METHODS

Mothers were interviewed within 1 year after delivery about sociodemographic factors, pregnancy events, and exposures. They were specifically asked if they experienced depression or anxiety or if they took any of the following SSRIs: citalopram, escitalopram, fluvoxamine, paroxetine, sertraline, or fluoxetine. We used logistic regression models to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

We included a total of 622 clubfoot cases and 2002 nonmalformed controls born between 2006 and 2011 in Massachusetts, New York, and North Carolina. For the 2nd or 3rd lunar month of pregnancy (the relevant gestational period), SSRI use for a period of more than 30 days was higher in case mothers (5%) than control mothers (3%). After adjustment for maternal smoking and body mass index, the OR for any SSRI use and clubfoot was 1.8 (95% CI = 1.1-2.8). When individual SSRIs were examined, ORs were elevated for sertraline (1.6 [0.8-3.2]), paroxetine (9.2 [0.7-484.6]), and escitalopram (2.9 [1.1-7.2]).

CONCLUSION

Our data suggest an increased risk of clubfoot occurrence in relation to SSRI use. Drug-specific risks varied widely, and some estimates were unstable.

Major malformations after first trimester exposure to aspirin and NSAIDs

The use of aspirin and other NSAIDs during the first trimester of pregnancy is widespread, despite inconclusive evidence regarding the possible risks for the baby. We present an overview of the current evidence relating to the associations between aspirin or NSAID use during the first trimester of pregnancy and the risk of congenital malformations. We systematically searched Medline, Embase, the Cochrane Library and the reference lists of all relevant articles from 1966 to March 2008 that examined the association between aspirin and NSAID use during the first trimester of pregnancy and the risk of congenital malformations in humans. We analyzed 30 studies that met the predefined inclusion criteria: 22 case-control studies, seven cohort studies and one randomized, controlled trial. There are not enough human data available to assess the effect of high-dose aspirin and NSAIDs in pregnant women, such as those used in the treatment of rheumatoid arthritis, osteoarthritis and pain relief. This review suggests that the exposure to aspirin or NSAIDs during the first trimester of pregnancy is associated with an increased risk of gastroschisis (aspirin), cardiac malformations (NSAIDs) and orofacial malformations (naproxen).

Normal and abnormal development of the cerebellum and brainstem as depicted by diffusion tensor imaging

Diffusion tensor imaging (DTI) is an advanced MRI technique that measures the microscopic molecular motion of water to gain information about the brain structure. This modality and its application to fiber tractography have been increasingly used in the last years to study the neuroanatomical background of brain malformations. This article aims to give an overview of the application of DTI and fiber tractography on pediatric posterior fossa including malformations, acquired disorders affecting the white matter, and posterior fossa involvement in phacomatoses. For every disorder, we show the additional information that DTI and fiber tractography are providing compared to conventional MR sequences and discuss their significance. Additionally, we show at the beginning normal DTI and fiber tractography findings of the pediatric posterior fossa. Finally, we briefly discuss potential future uses for DTI and fiber tractography to further understand the pathogenesis of posterior fossa malformations and the neuronal plasticity and connectivity of acquired lesions affecting the posterior fossa.

The first male with thoracoschisis: case report and review of the literature

A male infant presented at birth with intestine and liver herniated through a defect 3 cm below the left nipple on the anterior thoracic wall. Riedel lobe, attached to the left liver lobe, and the transverse colon were seen protruding through the defect at the region of the left eighth intercostal space at surgery. A fibrous band extending from the lower defect border to the bladder was present. The hernia content was reduced inside the abdomen and the fibrous band, and Riedel lobe and necrotic-appearing omentum were excised. Thoracoschisis is a very rare congenital anomaly with only 4 cases reported. This is the first isolated thoracoschisis case without an accompanying diaphragmatic hernia.

Amniotic band syndrome and/or limb body wall complex: split or lump

Six cases of amniotic band syndrome/limb body wall complex were studied in respect to clinicopathologic characteristics. The diagnosis was based on two out of three of the following manifestations: cranio facial clefts; limb body wall defects and amniotic band attachment. Four cases were stillborn and associated with internal defects, including central nervous system. Two cases had facial and limb defects and were live born (3-5 years old at examination). Phenotypic features of the stillborn cases were craniofacial clefting, thoracoabdominoschisis, amputation, ring constriction, amniotic band adhesion, placental adhesions, and internal malformations. Histology of bands revealed fibroconnective tissue as well as flattened epithelial cells together with neuroectodermal elements. Umbilical cord section revealed an abnormal number of vessels. When analyzing the observed data in relation to their etiology, it was found that amniotic disruption, vascular disruption or genetic disruption could explain the amniotic band syndrome/limb body wall complexes, alone or in combinations. A brief review of literature in search of pathogenesis is offered along with an etiopathogenetic model.

Morphological spectrum of prenatal cerebellar disruptions

There is increasing evidence that the cerebellum is susceptible to both prenatal infections and haemorrhages as well as being vulnerable in extremely preterm babies, but not to perinatal and postnatal hypoxic-ischaemic injuries. Starting with the imaging appearance we describe and illustrate a spectrum of prenatal cerebellar disruptions: cerebellar agenesis; unilateral cerebellar hypoplasia; unilateral cerebellar cleft; global cerebellar hypoplasia; vanishing cerebellum in myelomeningocele; and disruption of cerebellar development in preterm infants. We discuss neuroradiological characteristics, possible disruptive events, and clinical findings in the different morphological patterns. Remarkably, the same disruptive agent can cause different neuroradiological patterns, which appear likely to represent a morphological spectrum. The analysis of imaging patterns is crucial in recognising cerebellar disruptions. Recognition of cerebellar disruptions and their differentiation from cerebellar malformations is important in terms of diagnosis, prognosis, and genetic counselling.

Duodenal atresia with a deletion of midgut associated with left lung, kidney, and upper limb absences and right upper limb malformation

Duodenal atresia with midgut deletion without abdominal wall defects is extremely rare. The authors report a newborn boy with this disease associated with left pulmonary, kidney, and upper limb absences and a contralateral upper limb malformation. At autopsy, agenesis of the arteries to such organs was confirmed. A fetal vascular disruption is presumed to be the main cause of these anomalies.

Maternal febrile illnesses, medication use, and the risk of congenital renal anomalies

BACKGROUND

Renal anomalies occur in about three infants per 1000 live births and have been associated with several environmental risk factors. Researchers have yet to assess the effect of maternal febrile illnesses on renal anomalies, even though febrile illnesses have been associated with other birth defects. Our objective was to determine whether maternal illness, fever, or medication use during the first trimester of pregnancy is associated with the occurrence of renal anomalies.

METHODS

In this population-based case-control study, we evaluated 192 infants with renal anomalies (renal agenesis [n = 44], obstructive defects [n = 134], and renal duplication defects [n = 14]) and 3029 infant without birth defects, all of whom were born in metropolitan Atlanta, Georgia, from 1968 through 1980. Maternal illness was defined as reported flu-like illness and/or episodic illness during the first trimester.

RESULTS

Our adjusted multivariate analyses showed that among the 192 case-infants, 38 had mothers with an illness (adjusted odds ratio [AOR], 1.71; 95% confidence interval [CI], 1.15-2.52), 20 had mothers who reported a fever (AOR, 1.80; 95% CI, 1.07-3.02) and 26 had mothers who reported taking medication (AOR, 1.69; 95% CI, 1.07-2.68). Fifteen mothers reported a fever and medication use (AOR, 1.90; 95% CI, 1.05-3.45). Nonprescription aspirin-containing medication use showed the strongest association (AOR, 3.45; 95% CI, 1.36-8.75) with renal anomalies.

CONCLUSIONS

Our data suggest that maternal exposure to illness, fever, and medication (particularly aspirin) may increase the risk of congenital renal anomalies.

Guidelines for case classification for the National Birth Defects Prevention Study

BACKGROUND

Previous studies have suggested that etiologic heterogeneity may complicate epidemiologic analyses designed to identify risk factors for birth defects. Case classification uses knowledge of embryologic and pathogenetic mechanisms to make case groups more homogeneous and is important to the success of birth defects studies.

METHODS

The goal of the National Birth Defects Prevention Study (NBDPS), an ongoing multi-site case-control study, is to identify environmental and genetic risk factors for birth defects. Information on environmental risk factors is collected through an hour-long maternal interview, and DNA is collected from the infant and both parents for evaluation of genetic risk factors. Clinical data on infants are reviewed by clinical geneticists to ensure they meet the detailed case definitions developed specifically for the study. To standardize the methods of case classification for the study, an algorithm has been developed to guide NBDPS clinical geneticists in this process.

RESULTS

Methods for case classification into isolated, multiple, and syndrome categories are described. Defects considered minor for the purposes of case classification are defined. Differences in the approach to case classification for studies of specific defects and of specific exposures are noted.

CONCLUSIONS

The case classification schema developed for the NBDPS may be of value to other clinicians working on epidemiologic studies of birth defects etiology. Consideration of these guidelines will lead to more comparable case groups, an important element of careful studies aimed at identifying risk factors for birth defects.

Limb deficiencies in newborn infants

OBJECTIVE

The prevalence rate of all types of limb reduction defects in general and those that potentially are caused by vascular disruption in particular is needed to provide a baseline for the evaluation of infants who are exposed in utero to teratogens that cause vascular disruption. The objective of this study was to determine this prevalence rate.

METHODS

All infants with any limb deficiency among 161 252 liveborn and stillborn infants and elective terminations were identified in a hospital-based Active Malformations Surveillance Program in Boston in the years 1972 to 1974 and 1979 to 1994. An extensive search was made to identify infants who were missed by the Surveillance Program; an additional 8 infants (7.3% of total) were identified. The limb reduction defects were classified in 3 ways: 1) by the anatomic location of the defect, that is longitudinal, terminal, intercalary, etc; 2) for infants with absence/hypoplasia of fingers or toes, a tabulation of which digit or digits were affected; and 3) by apparent cause.

RESULTS

The prevalence rate for all types of limb deficiency was 0.69/1000. The apparent causes included single mutant genes, familial occurrence, and known syndromes (24%); chromosome abnormalities (6%); teratogens (4%); vascular disruption (35%); and unknown cause (32%).

CONCLUSIONS

A hospital-based surveillance program can be used to establish the prevalence of limb reduction defects, if ascertainment is extended to include elective terminations for fetal abnormalities. An apparent cause can be established for most limb defects when the clinical findings are used rather than reliance only on the International Classification of Diseases, Ninth Revision, codes of the discharge diagnoses. The prevalence rate of limb reduction defects as a result of presumed vascular disruption was 0.22/1000.

Tracheoesophageal malformation: pathogenetic evidence provided by two cases

BACKGROUND

The aim of this observational study is to examine cases of upper respiratory atresia, in an effort to seek pathogenetic evidence suggestive of either a primary defect in embryogenesis or of a secondary etiology.

METHODS

Archival material of 412 fetal and perinatal autopsies with congenital malformations was reviewed in an effort to identify infants with complete upper airway obstruction without tracheoesophageal (TE) communication. Histological sections of the upper and lower respiratory tract were examined, seeking evidence of previous amniotic fluid or meconium aspiration, indicated by the presence of amniotic squamous epithelial cells, lanugo hair, or bile-stained meconium in the airways. Immunohistochemical stain for epithelial membrane antigen (EMA) and high-molecular-weight cytokeratin (CK1) were used to identify amniotic fluid and keratinizing squamous epithelial cells.

RESULTS

Eight infants with upper airway obstruction were identified, three of them without a TE communication. Two of the latter, one infant with multiple atresia born at 34 weeks gestation and another with tracheal atresia born at 32 weeks, presented evidence of amniotic fluid aspiration in their lungs.

CONCLUSIONS

Evidence of amniotic fluid aspiration in the above two cases indicates that there had been a previous patency of the upper respiratory pathway, since the absence of a TE fistula excludes any communication with the oronasal cavity. This implicates a secondary pathogenesis for at least some cases of upper airway obstruction.

Prenatal diagnosis of a fetal abdominal cyst

Hepatic liver cysts are rare and few cases have been described in the literature. Initially, these cysts are detected by a prenatal ultrasound as abdominal, and consequently, the final diagnosis of hepatic cysts is done during the postnatal period. We present a case of a giant hepatic cyst found incidently during a routine ultrasound examination. The diagnosis and management of a fetal intraabdominal cyst is discussed.

Malformations reported in chorionic villus sampling exposed children: a review and analytic synthesis of the literature

PURPOSE

To determine whether the frequency of vascular disruption defects, other than limb defects, is increased in reports of chorionic villus sampling (CVS) exposed children compared with an unexposed population.

METHODS

Only studies that reported the total number of CVS-exposed pregnancies and details of pregnancy outcome, including all the malformations, were included. Twenty-five articles met these criteria.

RESULTS

The frequencies of gastroschisis, intestinal atresias, and clubfoot were significantly increased among the CVS-exposed infants as compared with the baseline unexposed population. The frequencies of other vascular disruption defects, including Poland sequence, amniotic band sequence, and cleft lip/cleft palate, were not increased.

CONCLUSION

CVS-exposed children have an increased frequency of intestinal atresia, gastroschisis, and clubfoot compared with the nonexposed population. The fact that an increased frequency of other defects attributed to vascular disruption was not found may be due to under-ascertainment, misclassification, or "lumping" of the defects identified in previous studies.

Methotrexate-resistant form of dihydrofolate reductase protects transgenic murine embryos from teratogenic effects of methotrexate

Methotrexate, a potent inhibitor of the ubiquitously expressed enzyme dihydrofolate reductase, induces limb and facial anomalies that resemble vascular disruptions in their evolution and final outcome. Previous studies suggest that inhibition of dihydrofolate reductase is responsible for methotrexate-induced embryopathy, although specific sites of methotrexate activity have not been well defined. In this report, we show that constitutive expression of a methotrexate-resistant form of dihydrofolate reductase in transgenic embryos and their placentas ameliorates methotrexate teratogenicity. However, expression of the transgene in maternal tissues had no significant protective effect. The results confirm the role of dihydrofolate reductase inhibition in the pathogenesis of methotrexate-induced birth defects and provide a foundation for future studies of targeted transgene expression in select embryonic or placental cell populations.

Association of single umbilical artery with congenital malformations of vascular etiology

The possible association of a single umbilical artery (SUA) with malformations of vascular etiology is investigated in this study. Four hundred twelve fetal and embryonic autopsies showing one or more congenital malformations, collected over 7 years, were reviewed. Microscopic confirmation of a SUA was evident in 20 cases (4.85%). The two subgroups with 2 (nA = 20) or 3 umbilical vessels (nB = 392) were compared with each other, in relation to the frequency of malformations per organ system. In the group of fetuses with congenital malformations, no association was observed between SUA and the incidence of CNS, cardiac, pulmonary, or genital malformations. However, there was a significantly higher incidence of atresia of hollow organs (P = 0.003), renal aplasia (P = 0.034), and limb reduction defects (LRD) (P = 0.0383) when only a single umbilical artery was present. This suggests a possible etiopathogenetic association of SUA with congenital malformations of vascular etiology. Furthermore, the findings of our study suggest that prenatal identification of a SUA warrants a thorough search for atresias, renal aplasia, and LRD-type malformations.

Limb reduction defects in the A/J mouse strain associated with maternal blood loss

We previously described a high incidence of digit/limb anomalies in the offspring of A/J mice subjected to surgery on day 12.5 postconception (p.c.), but not in the offspring of untreated control mice. To investigate the cause of these defects, we compared the offspring of mice in experimental groups involving adrenalectomy, sham adrenalectomy, blood sampling, and anesthesia with the offspring of control mice. All treatments significantly reduced fetal weight and increased resorptions as compared with the controls. The highest incidence of digit anomalies occurred in the offspring of dams from which blood samples had been drawn on days 12.5, 14.5, and 15.5 p.c. The incidence of isolated cleft palate was also increased in the offspring of mice that had been subjected to blood sampling. We conclude that digit anomalies in the offspring of A/J mice result from fetal vascular disruptive phenomena subsequent to maternal blood loss induced hypovolemia and hypoperfusion to the uterus and placenta as has been suggested for uterine vascular clamping, misoprostol, chorionic villus sampling, and cocaine teratogenesis. The etiology for cleft lip in these mice may involve mechanisms unrelated to uterine/placental hypoperfusion.

Pulmonary agenesis: a predictor of ipsilateral malformations

Pulmonary agenesis is a rare malformation that can be isolated or associated with other anomalies. We became interested in pulmonary agenesis after evaluation of a child with right pulmonary agenesis, an unlobed left lung, bilateral cleft lip and palate, maxillary and mandibular hypoplasia, bilateral microtia, bilateral radial ray hypoplasia, horseshoe kidney, and complex congenital heart disease. A review of the occurrence of pulmonary agenesis with other congenital anomalies uncovered a striking association with ipsilateral radial ray defects and/or hemifacial microsomia. The presence of bilateral facial or radial ray anomalies was indicative of bilateral pulmonary involvement. A review of the cases of pulmonary agenesis and associated anomalies at the Children's Hospital and Medical Center confirmed the association of pulmonary agenesis and ipsilateral involvement of face and/or radial ray. The association of pulmonary agenesis and ipsilateral malformations may shed light on its pathogenesis. Although the cause of these associated anomalies remains unclear, abnormalities in the development of the aortic arches during embryogenesis is an attractive hypothesis.

Limb defects and congenital anomalies of the genitalia in an infant with homozygous alpha-thalassemia

We describe an infant with homozygous alpha-thalassemia, genital abnormalities, and terminal transverse limb defects, whose limbs demonstrate evidence of loss of tissue and abnormal morphogenesis. We propose these defects were due to either severe fetal anemia or to vascular occlusion by abnormal erythrocytes, resulting in hypoxia of the developing distal limbs and genitalia.

Limb defects in homozygous alpha-thalassemia: report of three cases

Homozygosity for the South-Asian alpha-thalassemia (--SEA/) deletion is a serious hematological condition that results, in most cases, in intrauterine or postnatal death due to anemia and severe hypoxia of prenatal onset. A relationship between congenital abnormalities and intra-uterine hypoxia has been postulated. However, since homozygosity for the (--SEA/) deletion is most common in underdeveloped countries where detailed autopsies are lacking, the incidence of congenital abnormalities among these babies has not been well delineated. We report on three newborn infants, homozygous for the (--SEA/) deletion, who were born with limb defects. We postulate that this combination is the result of prenatal hypoxia which may affect other fetal body organs. This should be taken into consideration when prenatal treatment of affected fetuses, with intrauterine blood transfusion, is suggested.

A familial disorder with duodenal atresia and tetralogy of Fallot

We report on two sibs with tetralogy of Fallot (TOF) and duodenal atresia (DA). The first child, a 6-year-old girl, had a right facial palsy in addition to the TOF and DA. Her brother, age 10 months, was born with bilateral microtia without facial palsy. The children are the product of an apparently non-consanguineous union between clinically normal parents. The pertinent family history includes a paternal aunt with TOF and a cleft lip and palate who died in childhood and another paternal aunt with a supernumerary thumb. This family has anomalies found in several syndromes, but does not meet the diagnostic criteria for any of them. The genetic basis for this condition remains unknown, but the pattern of inheritance is likely either autosomal recessive, or autosomal dominant with variable expression and reduced penetrance. The pathogenesis is unknown, but either a disturbance in neural crest cell migration or familial predisposition to vascular disruption might explain this pattern of malformations.

Heterogeneous rates for birth defects in Latin America: hints on causality

The aim of this work was to disclose risk factors associated with birth defects which were heterogeneously distributed in the different geographic regions sampled by the Latin American Collaborative Study of Congenital Malformations (ECLAMC). The material included 2,159,065 hospital births, delivered in the 1967-1989 period in 24 geographic regions of Latin America. Birth defect types with 50 case-control pairs or more were analyzed. A risk factor was defined as that available variable with differential geographic rates, correlated with those of a given birth defect type. Identified factors were tested by case-control multivariate logistic regression to confirm their role in the occurrence of the defect. Altitude and maternal acute illness during first trimester of pregnancy, named influenza, were risk factors for microtia. Prenatal drug exposure, mainly sex hormones, were connected with the occurrence of hypospadias in low frequency areas, while Native ancestry was a "protective" factor in the same regions. Acute (influenza), and chronic (epilepsy and syphilis) maternal illness during first trimester of pregnancy and gravidity higher than four were risk factors for cleft lip. The independence of these variables from maternal age suggested that low maternal socioeconomic level could explain the high birth defect order and, perhaps, syphilis in mothers. Postaxial polydactyly was associated with parental consanguinity, as well as Afro-American ancestry, suggesting genetic heterogeneity.

Hepatic cysts and hyperechogenicities: perinatal assessment and unifying theory on their origin

The authors report their experience with the perinatal diagnosis of six cases of hepatic cyst and six of liver hyperchogenicities. The in utero diagnosis of hepatic cysts was difficult when the cysts were large or subhepatic. A precise diagnosis was sometimes achieved only after surgery. Small intraparenchymal cysts tended to regress spontaneously. Liver hyperechogenicities were diffuse or localized. They were unrelated to liver infection, tumors, meconium peritonitis or biliary tract anomaly. Both entities could be related to vascular disruption phenomenon (VDP) in which structural anomalies result from damage to normal development of embryonic or fetal vessels with anomalies of perfusion to the developing organs. The consequences of VDP to the liver are variable depending on the time and duration of the phenomenon. Localized infarct or ischemia can fibrose or calcify leading to segmental hyperechogenicities. Necrosis with tissue reabsorption can be the origin of some (sub)hepatic cysts. When such anomalies are detected there should be a careful study of the placentation, and a search for potential associated anomalies should be undertaken.

Evidence for multi-site closure of the neural tube in humans

Four separate initiation sites for neural tube (NT) fusion have been demonstrated recently in mice and other experimental animals. We evaluated the question of whether the multisite model vs. the traditional single-site model of NT closure provided the best explanation for neural tube defects (NTDs) in humans. Evidence for segmental vs. continuous NT closure was obtained by review of our recent clinical cases of NTDs and previous medical literature. With the multi-site NT closure model, we find that the majority of NTDs can be explained by failure of fusion of one of the closures or their contiguous neuropores. We hypothesize that: Anencephaly results from failure of closure 2 for meroacranium and closures 2 and 4 for holoacranium. Spina-bifida cystica results from failure of rostral and/or caudal closure 1 fusion. Craniorachischisis results from failure of closures 2, 4, and 1. Closure 3 non-fusion is rare, presenting as a midfacial cleft extending from the upper lip through the frontal area ("facioschisis"). Frontal and parietal cephaloceles occur at the sites of the junctions of the cranial closures 3-2 and 2-4 (the prosencephalic and mesencephalic neuropores). Occipital cephaloceles result from incomplete membrane fusion of closure 4. In humans, the most caudal NT may have a 5th closure site involving L2 to S2. Closure below S2 is by secondary neurulation. Evidence for multi-site NT closure is apparent in clinical cases of NTDs, as well as in previous epidemiological studies, empiric recurrence risk studies, and pathological studies. Genetic variations of NT closures sites occur in mice and are evident in humans, e.g., familial NTDs with Sikh heritage (closure 4 and rostral 1), Meckel-Gruber syndrome (closure 4), and Walker-Warburg syndrome (2-4 neuropore, closure 4). Environmental and teratogenic exposures frequently affect specific closure sites, e.g., folate deficiency (closures 2, 4, and caudal 1) and valproic acid (closure 5 and canalization). Classification of NTDs by closure site is recommended for all studies of NTDs in humans.(ABSTRACT TRUNCATED AT 400 WORDS)