Multiple congenital anomalies associated with oral anticoagulants

Maternal Cigarette Smoking and Congenital Upper and Lower Limb Differences: A Systematic Review and Meta-Analysis

Maternal smoking during pregnancy has been associated with adverse effects on foetal development, including congenital limb anomalies. This systematic review aimed to provide an updated assessment of the association between maternal smoking during pregnancy and the risk of congenital limb anomalies. A systematic search was conducted to identify relevant studies published up to February 2023. Studies reporting on the relationship between maternal smoking during pregnancy and congenital digital anomalies or congenital limb reduction defects were included. Two independent reviewers screened the studies, extracted data, and assessed the quality of the included studies. Meta-analyses were performed to estimate the pooled odds ratios with 95% confidence intervals using fixed and random-effects models. In total, 37 publications comprising 11 cohort and 26 case-control studies were included in the systematic review. The meta-analysis demonstrated a significant increased risk of congenital limb reduction defects (pooled OR: 1.27, 95% CI: 1.18-1.38) in infants born to mothers who smoked during pregnancy. Similarly, a significant relationship was observed for the development of polydactyly/syndactyly/adactyly when considered as a single group (pooled OR: 1.32, 95% CI: 1.25-1.40). Yet, in contrast, no significant association was observed when polydactyly (pooled OR: 1.06, 95% CI: 0.88-1.27) or syndactyly (pooled OR: 0.91, 95% CI: 0.77-1.08) were considered individually. This systematic review provides updated evidence of a significant relationship between maternal smoking during pregnancy and increased risk of congenital limb anomalies. These findings highlight the potential detrimental effects of smoking on foetal limb development and underscore the importance of smoking cessation interventions for pregnant women to mitigate these risks.

Another look at reactions of 4-hydroxycoumarin with hydroxyl radical in the environment: deprotonation and diffusion effects

Quantum chemistry calculations suggest that chemical fate of the anticoagulant rodenticide 4-hydroxycoumarin in the environment is crucially dependent on deprotonation in aqueous medium.

A novel screening test to predict the developmental toxicity of drugs using human induced pluripotent stem cells

In vitro human induced pluripotent stem (iPS) cells testing (iPST) to assess developmental toxicity, e.g., the induction of malformation or dysfunction, was developed by modifying a mouse embryonic stem cell test (EST), a promising animal-free approach. The iPST evaluates the potential risks and types of drugs-induced developmental toxicity in humans by assessing three endpoints: the inhibitory effects of the drug on the cardiac differentiation of iPS cells and on the proliferation/survival of iPS cells and human fibroblasts. In the present study, the potential developmental toxicity of drugs was divided into three classes (1: non-developmentally toxic, 2: weakly developmentally toxic and 3: strongly developmentally toxic) according to the EST criteria. In addition, the type of developmental toxicity of drugs was grouped into three types (1: non-effective, 2: embryotoxic [inducing growth retardation/dysfunction]/deadly or 3: teratogenic [inducing malformation]/deadly) by comparing the three endpoints. The present study was intended to validate the clinical predictability of the iPST. The traditionally developmentally toxic drugs of aminopterin, methotrexate, all-trans-retinoic acid, thalidomide, tetracycline, lithium, phenytoin, 5-fluorouracil, warfarin and valproate were designated as class 2 or 3 according to the EST criteria, and their developmental toxicity was type 3. The non-developmentally toxic drugs of ascorbic acid, saccharin, isoniazid and penicillin G were designated as class 1, and ascorbic acid, saccharin and isoniazid were grouped as type 1 while penicillin G was type 2 but not teratogenic. These results suggest that the iPST is useful for predicting the human developmental toxicity of drug candidates in a preclinical setting.

High-Versus Low-Dose Warfarin-Related Teratogenicity: A Case Report and Systematic Review

OBJECTIVE

The optimal anticoagulant therapy during pregnancy in women with mechanical heart valves remains controversial. This study highlights a case of high-dose warfarin ingestion throughout pregnancy and performed a systematic review to assess rates of teratogenicity with high versus low warfarin dosing (≤5 mg daily).

METHODS

A literature search for all case reports and available literature was conducted in PubMed, Medline, and EMBASE up to December 2016 using medical subject heading terms "mechanical prosthetic valves," "pregnancy," "oral anticoagulants," "warfarin," "coumarins," "heparin, low-molecular-weight," and "thromboembolism." To be included, warfarin had to be administered anytime between 6 and 12 weeks of gestation with the dose being specified. The Newcastle-Ottawa Scale was used to assess quality of the cohort data.

RESULTS

The woman in the studied case received the highest reported warfarin doses throughout pregnancy (14.5-16.5 mg daily) and delivered a baby with no evidence of teratogenicity to the current age of 5 years. The study identified 23 case reports, with all demonstrating warfarin teratogenicity regardless of high-dose (n = 12) or low-dose (n = 11) warfarin. Twelve cohort studies identified a warfarin teratogenicity rate of 5.0%, with rates of 2.4% and 10.5% with low- and high-dose warfarin, respectively. Risk of bias was moderate (median Newcastle-Ottawa Scale score of 6) for all of the cohort studies.

CONCLUSION

Although a lower prevalence of warfarin-induced teratogenicity is reported with low-dose warfarin, a safe "cut-off" dose is misleading. Teratogenic risk with warfarin is unpredictable, mandating individual decisions regardless of the dose.

Management dilemmas in acute pulmonary embolism

Background

Physicians treating acute pulmonary embolism (PE) are faced with difficult management decisions while specific guidance from recent guidelines may be absent.

Methods

Fourteen clinical dilemmas were identified by physicians and haematologists with specific interests in acute and chronic PE. Current evidence was reviewed and a practical approach suggested.

Results

Management dilemmas discussed include: sub-massive PE, PE following recent stroke or surgery, thrombolysis dosing and use in cardiac arrest, surgical or catheter-based therapy, failure to respond to initial thrombolysis, PE in pregnancy, right atrial thrombus, role of caval filter insertion, incidental and sub-segmental PE, differentiating acute from chronic PE, early discharge and novel oral anticoagulants.

Conclusion

The suggested approaches are based on a review of the available evidence and guidelines and on our clinical experience. Management in an individual patient requires clinical assessment of risks and benefits and also depends on local availability of therapeutic interventions.

Teratogenic exposures

A consideration of teratogenic exposures includes not only an agent (chemical, radiation, biologic) but an exposure level and timing of exposure. There are criteria by which exposures are evaluated for a causal connection with an abnormal outcome. We here review some teratogenic exposures and discuss how they were initially described and confirmed. We have limited our discussion to some of the exposures for which a connection to structural malformations has been accepted in some quarters, and we indicate some exposures for which a causal association awaits confirmation. We recommend that counselors find a reliable and updatable source of information on exposures during pregnancy.

Guidelines on the diagnosis and management of acute pulmonary embolism: the Task Force for the Diagnosis and Management of Acute Pulmonary Embolism of the European Society of Cardiology (ESC)

Non-thrombotic PE does not represent a distinct clinical syndrome. It may be due to a variety of embolic materials and result in a wide spectrum of clinical presentations, making the diagnosis difficult. With the exception of severe air and fat embolism, the haemodynamic consequences of non-thrombotic emboli are usually mild. Treatment is mostly supportive but may differ according to the type of embolic material and clinical severity.

Range of Alcohol-Induced Damage in the Developing Central Nervous System

Fourteen previously reported cases of the fetal alcohol syndrome (FAS) showed anomalies of brain structure varying in severity from microscopic disorganization of tissue structure, or abnormalities in neuronal or glial migration only visible microscopically, to complete or partial agenesis of regions such as the corpus callosum or cerebellum and large neuronal heteropias. The difficulty is illustrated of differentiating this type of damage, lacking in specificity and uniformity, from other syndromes of uncertain aetiology, such as De Lange, DiGeorge and Dubowitz, in at least one of which (DiGeorge syndrome) maternal alcoholism has been implicated. Similar brain damage is also seen in other conditions with known causes. In FAS and syndromes with this type of brain damage, most of the non-CNS features which make the conditions clinically recognizable may well be determined by timing or ancillary factors. Alcohol-related antenatal effects should not be identified to restrictively with FAS but should be considered in any condition of unknown aetiology with disorganization of brain structure and mental retardation.

MECHANICAL HEART VALVES AND PREGNANCY

Mechanical heart valves pose a particular challenge in pregnancy, as the primary agent used to prevent valve thrombosis, coumadin (warfarin), is a known teratogen. Alternatives to coumadin, such as unfractionated heparin (UFH) and low-molecular weight heparin (LMWH) are safer for the fetus, particularly during the first trimester of pregnancy, but expose the mother to potential valve failure. This review will examine these controversies and the complex literature regarding management in pregnancy.

Maternal cigarette smoking during pregnancy increases the risk of having a child with a congenital digital anomaly

BACKGROUND

The U.S. Natality database from 2001 and 2002 was used to investigate the relationship between maternal cigarette smoking during pregnancy and the risk of having a child with polydactyly, syndactyly, or adactyly.

METHODS

The records of 6,839,854 live births were examined to identify 5171 newborns with isolated polydactyly, syndactyly, or adactyly and 10,342 controls with no congenital anomalies.

RESULTS

Maternal cigarette use during pregnancy was associated with a significantly elevated risk of having a child with a congenital digital anomaly (unadjusted odds ratio, 1.33; 95 percent confidence interval, 1.21 to 1.47; p < 0.0001). Univariate analysis indicated that maternal marital status and medical risk factors (anemia, cardiac disease, lung disease, diabetes, hydramnios/oligohydramnios, pregnancy-associated hypertension, incompetent cervix, previous preterm or small-for-gestational-age infant, and rhesus factor sensitization) were potential confounding factors. After adjustment for these variables, the odds ratio remained significant (adjusted odds ratio, 1.31; 95 percent confidence interval, 1.18 to 1.45; p < 0.0001). Cigarette consumption per day was divided into four groups: no smoking, 1 to 10 cigarettes per day, 11 to 20 cigarettes per day, and 21 or more cigarettes per day. A statistically significant dose-response relationship was found when comparing each smoking category with the no-smoking reference group: 1.29 (95 percent confidence interval, 1.15 to 1.46), 1.38 (95 percent confidence interval, 1.12 to 1.71), and 1.78 (95 percent confidence interval, 0.97 to 3.26), respectively. Increased cigarette smoking during pregnancy resulted in an elevated risk of having a child with polydactyly, syndactyly, or adactyly.

CONCLUSIONS

This is the largest study to date to investigate specifically the association between maternal cigarette smoking and the risk of having a newborn with a congenital digital anomaly. The elevated odds ratio for tobacco use and the significant trend in the dose-response relationship suggests smoking during pregnancy may be an important preventable risk factor for these common congenital differences.

Obstetric complications due to autoantibodies

Autoimmune diseases are most common and most active in young women; it is therefore not uncommon for obstetricians and physicians to encounter pregnant women with these conditions, and knowledge of the potential maternal, foetal and neonatal complications is essential for good clinical management. The most common maternal autoimmune endocrine conditions in pregnancy are insulin-dependent diabetes mellitus and thyroid disease. Other relatively common non-endocrine autoimmune conditions include systemic lupus erythematosus and anti-phospholipid syndrome. Much rarer autoimmune conditions include autoimmune thrombocytopenia, rheumatoid arthritis, myasthenia gravis and Addison's disease. In this chapter, we discuss autoimmune endocrine conditions and briefly mention some non-endocrine conditions of particular importance.

Abnormal fetal growth: intrauterine growth retardation, small for gestational age, large for gestational age

The two extremes of abnormal fetal growth are restricted growth and excessive growth, both of which originate from alterations in the uterine metabolic milieu. The fetus must adapt to these conditions to survive. In both instances, however, the inciting insult and the subsequent adaptation of the fetus carry long-term health consequences. In some instances, these changes may have generational implications. Counseling and care by pediatricians should be directed at the continuum of age ranges, including the expectant mother, the newborn, the child and adolescent, and future generations.

Labor analgesia for the parturient with cardiac disease: what does an obstetrician need to know?

Maternal heart disease complicates 0.2-3% of pregnancies. The optimal management of the pregnant patient with cardiac disease depends on the cooperative efforts of the obstetrician, the cardiologist and the anesthesiologist involved in peripartum care. A comprehensive understanding of physiology of pregnancy and pathophysiology of underlying cardiac disease is of primary importance in provision of obstetric analgesia or anesthesia for this high-risk group of patients. This article will review the current guidelines and standards pertinent to management of obstetric analgesia and anesthesia in parturients with cardiac disease.

Teratogen-induced limb defects

Limb abnormalities are one of the most common and visible phenotypic effects of several human teratogens. The specific effects are different for most teratogens and include effects on limb morphogenesis (thalidomide, warfarin, phenytoin, valproic acid) and the effect of vascular disruption on a limb that had formed normally (misoprostol, chorionic villus sampling, and phenytoin). Either duplication (preaxial polydactyly of hands and feet) or deficiency (absence of thumb) is a common effect of thalidomide; no other human teratogen identified to date has this effect on the developing limb. Procedures during pregnancy, including chorionic villus sampling and dilation and curettage, produce defects of vascular disruption. For common exposures, such as alcohol and cocaine, it has been difficult to confirm objectively the exposure during embryogenesis and to ascribe specific limb defects that are produced. The molecular basis for the limb defects produced by the recognized human teratogens remains unknown.

Anticoagulant therapy in pregnancy

Anticoagulation during pregnancy should derive benefit from recent advances in anticoagulant therapy. Unfractionated heparin is at present the drug of choice for most of the indications of thromboprophylaxis as well as for acute venous thrombosis during pregnancy but it is likely that, in the near future, low molecular weight heparins will supercede this anticoagulant in many indications. One particular indication is mechanical heart valves that needs a high degree of anticoagulation. The anticoagulant of choice that carries the best efficacy-risk ratio in this situation seems to be oral anticoagulants. Pregnant women receiving anticoagulation should be considered as high-risk patients that should be managed in specialized centres. They are prone to bleeding complications that will mainly occur during delivery or in the postpartum period.

Evaluation of the developmental toxicities of coumarin, 4-hydroxycoumarin, and 7-hydroxycoumarin using FETAX

The developmental toxicities of coumarin and hydroxycoumarin metabolites were evaluated using FETAX. Young X. laevis embryos were exposed to coumarin, 4-hydroxycoumarin, and 7-hydroxycoumarin in each of two separate concentration-response experiments with and without an exogenous metabolic activation system (MAS) and/or inhibited MAS. The MAS was treated with carbon monoxide (CO), cimetidine (CIM), or ellipticine (ELL) to selectively modulate cytochrome P-450 activity. The MAS was also treated with cyclohexene oxide (CHO) to selectively modulate epoxide hydrolase activity. Without the MAS or inhibited MAS, coumarin and 7-hydroxycoumarin were nearly equitoxic, whereas 4-hydroxycoumarin was nearly 2-fold less developmentally toxic than coumarin on an equimolar basis. Addition of the MAS and CIM-MAS increased the developmental toxicities of coumarin and, particularly, 4-hydroxycoumarin. Addition of the CHO-MAS greatly increased the developmental toxicity of coumarin and, especially, 4-hydroxycoumarin. Addition of the ELL- or CO-inhibited MAS did not increase the developmental toxicity of coumarin. However, addition of the intact MAS did not alter the developmental toxicity of 7-hydroxycoumarin. Results from these studies suggested that P-450; specifically ELL-inhibited P-450 (arylhydrocarbon hydroxylase) may have been responsible for increasing the developmental toxicity of coumarin. Furthermore, the increased toxicity of coumarin or 4-hydroxycoumarin following co-incubation with CHO-treated microsomes indicated that highly toxic epoxide intermediates may be produced from oxidative P-450 metabolism and that epoxide hydrolase may play a role in detoxification of the reactive intermediates.

Severe cervical dysplasia and nasal cartilage calcification following prenatal warfarin exposure

We present an infant who was exposed to warfarin throughout pregnancy and has warfarin embryopathy. When the child was examined radiologically at 20 months areas of calcification were visible in the septal and alar cartilages of the small external part of the nose. The location of this ectopic calcification is consistent with that seen in an animal model of the warfarin embryopathy. It supports the hypothesis that warfarin interferes with the prenatal growth of the cartilaginous nasal septum by inhibiting the normal formation of a vitamin K-dependent protein that prevents calcification of cartilage. The child also had severe abnormalities of the cervical vertebrae and secondary damage to the spinal cord. Cervical vertebral anomalies are a relatively common finding in the warfarin embryopathy and in the related Binder syndrome.

Anticoagulants in pregnancy: fetal effects

Anticoagulants are used during pregnancy to prevent venous thrombo-embolism in highrisk patients, to prevent systemic embolism in patients with prosthetic heart valves or native valvular heart disease, and to treat patients with acute venous thrombo-embolism. Neither unfractionated nor low-molecular-weight heparin cross the placenta and both appear to be safe for the fetus. Oral anticoagulants do cross the placenta and they have been associated with the development of warfarin embryopathy, central nervous system anomalies, and fetal haemorrhage. The true incidence of these events is not known. Both heparin and oral anticoagulants can be safely administered to nursing mothers.

Venous thromboembolism during pregnancy: a current review of diagnosis and management

Pregnancy is widely recognized to be a physiologic state with a markedly elevated risk for thromboembolic complications. The diagnosis and management of venous thromboembolic events during pregnancy, however, remains controversial because of the lack of prospective, randomized trials that have included pregnant women. Significant progress has been made in the last 10 years in the management of these conditions in the nonpregnant patient and strong clinical guidelines have been established recently. Obstetrician-gynecologists may modify these guidelines and apply them to the pregnant patient based on their knowledge of the physiologic changes in pregnancy. Objective diagnostic techniques should be used liberally when the diagnosis of deep vein thrombosis or pulmonary emboli is considered because early intervention may prevent serious maternal sequelae including death. Heparin remains the anticoagulant of choice during pregnancy because of its proven safety for both the patient and the fetus. It is likely that long-term anticoagulation is necessary when venous thromboembolism occurs antepartum, although the most efficacious regimen has yet to be established. There is some concern about the prolonged use of heparin during pregnancy, particularly regarding the risk of osteopenia.

Differential effects of warfarin on mRNA levels of developmentally regulated vitamin K dependent proteins, osteocalcin, and matrix GLA protein in vitro

The role of the vitamin K dependent proteins, osteocalcin which is bone specific and matrix Gla protein (MGP) found in many tissues, has been studied by inhibition of synthesis of their characteristic amino acid, gamma-carboxyglutamic acid (Gla) with the anticoagulant sodium warfarin. The effect of sodium warfarin on expression of these proteins, and other phenotypic markers of bone and cartilage during cellular differentiation and development of tissue extracellular matrix, was examined in several model systems. Parameters assayed include cell growth (reflected by histone gene expression) and collagen types I and II, osteopontin, alkaline phosphatase, and mineralization. Studies were carried out in calvarial bone organ cultures, normal diploid rat osteoblast and chondrocyte cultures, and rat osteosarcoma cell lines ROS 17/2.8 and 25/1. In normal diploid cells, warfarin consistently stimulated cell proliferation (twofold). In osteoblast cultures, MGP mRNA levels were generally increased (three to tenfold). Notably, MGP mRNA levels were not affected in chondrocyte cultures, either with chronic or acute warfarin treatments. Osteocalcin mRNA levels and synthesis were decreased up to 50% in ROS 17/2.8 cells and in chronically treated (1 and 5 micrograms/ml sodium warfarin) rat osteoblast cultures after 22 days. Early stages of osteoblast phenotype development from the proliferation period to initial tissue formation (nodules) appeared unaffected; while after day 14, further growth and mineralization of the nodule areas were significantly decreased in warfarin-treated cultures. In summary, warfarin has opposing effects on the expression of two vitamin K dependent proteins, MGP and osteocalcin, in osteoblast cultures and MGP is regulated differently between cartilage and bone as reflected by cellular mRNA levels. Additionally, warfarin effects expression of nonvitamin K dependent proteins which may reflect the influence of warfarin on endoplasmic reticulum associated enzymes.

Anticoagulants in pregnancy

Pregnancy is associated with a prethrombotic state. Pulmonary embolism is the major cause of maternal mortality. Anticoagulant prophylaxis and therapy are therefore commonplace in pregnant women. Those with inherited and acquired thrombophilic conditions are at increased risk and special considerations arise in management. Heparin has recently become the favoured anticoagulant drug in pregnancy. Its use carries risks of osteopaenia and thrombocytopaenia, as well as haemorrhage, in the mother. Warfarin is teratogenic and may also cause haemorrhagic complications in mother and fetus. Few clinical trial data exists for guidance on optimal anticoagulant regimes during pregnancy and the puerperium and details of management will depend upon the personal preferences of patient and clinician, after due consideration of the perceived risks and benefits in the individual clinical situation.

Fetal and neonatal outcome of exposure to anticoagulants during pregnancy

We studied fetal and neonatal outcome of women maintained on anticoagulants (warfarin and/or heparin) during pregnancy. Among 22 Chinese families, 13 mothers (59%) had a history of recurrent abortion or stillbirth while being maintained on warfarin treatment. Twenty-nine liveborn children (17 boys, 12 girls), ages 0.6-11.3 years at follow-up, were analysed for evidence of embryopathy. These were subdivided into 2 groups. Group 1 consisted of 18 children (12 boys, 6 girls) whose mothers were only given warfarin during pregnancy. Five were small for gestational age, and 12 had features of warfarin embryopathy such as nasal hypoplasia. One had subependymal intraventricular hemorrhage shown on neonatal ultrasonography. Group 2 consisted of 11 children (5 boys, 6 girls) whose mothers were maintained on warfarin and heparin during pregnancy. Three were premature deliveries, and 4 had nasal hypoplasia. One had cleft lip, cleft palate, cataract, microphthalmia, intraventricular hemorrhage, and hydrocephalus. We found that despite the high risk of fetal wastage, there was a relative lower risk of major complications, except for some minor cosmetic defects such as nasal hypoplasia. This might lead to readjustment of advice concerning contraception given to pregnant women who were maintained on anticoagulant therapy.

Binder's syndrome due to prenatal vitamin K deficiency: a theory of pathogenesis

There is evidence that vitamin K-deficiency during human pregnancy can be caused by the therapeutic use of warfarin or phenytoin. The pregnancy histories of three cases of Binder's syndrome are reported. One was associated with warfarin exposure, one with phenytoin exposure and one with alcohol abuse. It is proposed that Binder's syndrome can be caused by prenatal exposure to agents that cause vitamin K-deficiency. Sprague-Dawley rats were treated from postnatal day 1 to 12 weeks with daily doses of warfarin (100 mg/kg) and concurrent vitamin K1 (10 mg/kg). This regimen creates a net extra-hepatic vitamin K-deficiency. The treated rats developed with a distinct facial appearance characterized by a markedly reduced snout. Histological examination showed that the normally non-calcified septal cartilage was extensively calcified. It is proposed that normal growth of the septal cartilage is necessary for the development of the profile of the nose and midface and that normal growth will only take place while the septal cartilage is uncalcified.

The warfarin embryopathy: a rat model showing maxillonasal hypoplasia and other skeletal disturbances

Sprague-Dawley rats were given daily subcutaneous doses of sodium warfarin (100 mg/kg) and vitamin K1 (10 mg/kg) for up to 12 weeks, starting on the day after birth. This dosing regimen creates an extrahepatic vitamin K deficiency while preserving the vitamin K-dependent processes of the liver. Control rats received either vitamin K1 only or were untreated. All rats survived without any signs of hemorrhage. The warfarin-treated rats developed a marked maxillonasal hypoplasia associated with a 11-13% reduction in the length of the nasal bones compared with controls. The length of the posterior part of the skull was not significantly different from controls. In the warfarin-treated rats, the septal cartilage of the nasal septum showed large areas of calcification, not present in controls, and abnormal calcium bridges in the epiphyseal cartilages of the vertebrae and long bones. The ectopic calcification in the septal cartilage may have been the cause of the reduced longitudinal growth of the nasal septum and the associated maxillonasal hypoplasia. It is proposed that (1) the facial features of the human warfarin embryopathy are caused by reduced growth of the embryonic nasal septum, and (2) the septal growth retardation occurs because the warfarin-induced extrahepatic vitamin K deficiency prevents the normal formation of the vitamin K-dependent matrix gla protein in the embryo.

Teratology in pediatric practice

A range of infections, physical agents, maternal diseases and metabolic states, drugs, and chemicals have been demonstrated to be human teratogens. These agents cause structural or functional disabilities postnatally in exposed embryos and fetuses. Such disabilities are potentially totally preventable through public education and awareness. Pediatricians must be able to recognize potential teratogenic exposures, diagnose teratogenically-induced disabilities, and be knowledgeable in the natural history of these disorders so that they can support and educate those who care for these children in the home and in the community.

Ocular teratology

The principles of teratology are described, and animal models for research in abnormal ocular development and clinical studies of human teratogens are surveyed. A review is made of presumed ocular teratogenic agents: radiation; external environmental teratogens; maternal conditions such as infections, diabetes, and epilepsy; alcohol and drugs such as thalidomide, retinoic acid, and coumarin anticoagulants; and other agents, such as cigarettes.

Assessment of the developmental toxicity of ascorbic acid, sodium selenate, coumarin, serotonin, and 13-cis retinoic acid using FETAX

The developmental toxicity of five compounds was evaluated with the Frog Embryo Teratogenesis Assay: Xenopus (FETAX) and the results were compared to mammalian literature. Small cell Xenopus laevis blastulae were exposed to ascorbic acid, sodium selenate, coumarin, serotonin and 13-cis retinoic acid for 96 hr. Three separate static-renewal assays were conducted for each compound. Teratogenic potential of the test materials was determined based on Teratogenic Index values [TI = LC50/EC50 (malformation)], types and severity of induced malformations and embryo growth. Ascorbic acid had little or no teratogenic potential. Sodium selenate and coumarin tested as having moderately positive teratogenic potential. Serotonin scored as having moderately strong teratogenic potential and 13-cis retinoic acid scored as having strong teratogenic potential. Results were consistent with mammalian data and support the use of FETAX for the screening of developmental toxicants.

Exposure of the pregnant rat to warfarin and vitamin K1: an animal model of intraventricular hemorrhage in the fetus

Pregnant Sprague-Dawley rats were given daily oral doses of sodium warfarin (100 mg/kg) and concurrent intramuscular injections of vitamin K1 (10 mg/kg). This dosing regimen did not have any apparent deleterious effect on the dams and did not affect the fetuses when administered from day 1 to day 12 of pregnancy. However, similar treatment from day 9 to 20 caused hemorrhage in the fetuses examined on day 21 of gestation. There were no hemorrhages in the control fetuses from dams receiving vitamin K1 only. The lowest effective dose of warfarin, in conjunction with daily doses of vitamin K1, was 3 mg/kg. This dose caused hemorrhage in 28% of fetuses; the incidence of affected fetuses was not further increased by doses of warfarin up to 100 mg/kg. Hemorrhages affected the fetal brain, face, eyes, and ear and occasionally the limbs. Brain hemorrhages were frequently intraventricular and caused various degrees of hydrocephaly. Bony defects were not a feature of prenatal exposure to warfarin. These results show that prenatal exposure of the rat to warfarin and vitamin K duplicates the hemorrhagic abnormalities and pathology associated with prenatal exposure to warfarin in the human. It did not induce bony or facial defects probably because the vitamin K-dependent components of bone development occur postnatally in the rat. This model should allow detailed determination of the role of vitamin K-dependent proteins in development.

Effect of sodium warfarin on vitamin K-dependent proteins and skeletal development in the rat fetus

Sodium warfarin was administered daily to Sprague-Dawley rats from gestational day 8 to day 22 to examine the effects of this compound on the developing fetal skeleton and on the vitamin K-dependent bone and cartilage proteins. At a dose of 175 micrograms/kg of sodium warfarin there was a 43% mortality rate among the dams. Maternal prothrombin times and serum osteocalcin levels were slightly elevated but not significantly. In the surviving litters, fetal bone osteocalcin and gamma-carboxyglutamic acid were significantly reduced (50 and 57%, respectively, on gestational day 22) when compared to age- and/or weight-matched control pups. The high correlation of osteocalcin content in long bone (R = 0.64) and calvariae (R = 0.77) to fetal body weight observed in control fetuses was not seen in the warfarin-exposed pups. Examination of alizarin-stained warfarin-exposed fetal skeletons for ossification centers showed no difference from controls. However, analysis of the tibial growth showed several changes compared to control that included (1) widened hypertrophic zones, (2) increased calcification of the hypertrophic zones, and (3) disorganization of the hypertrophic cells. These results suggest that the growth plate abnormalities seen with prenatal warfarin exposure relate to the inhibition of the vitamin K-dependent proteins of the skeletal system.

Normal ionized calcium, parathyroid hypersecretion, and elevated osteocalcin in a family with fluorosis

Sera from five patients with skeletal fluorosis were investigated for total calcium, ionized calcium, phosphate, alkaline phosphatase, 25 hydroxyvitamin D (25 OHD), 1,25 dihydroxyvitamin D (1,25[OH]2D), parathyroid hormone, and osteocalcin concentrations. Total and ionized calcium concentrations were normal in four and subnormal in one, but PTH concentration was elevated in all five. The patient with a subnormal calcium concentration also had subnormal 25 OHD and 1,25(OH)2D concentrations and a supranormal PTH concentration. The remaining four had supranormal PTH concentrations despite normal total and ionized calcium concentration, and normal 25 OHD and 1,25(OH)2D levels. Osteocalcin concentration was markedly elevated in all patients, as was alkaline phosphatase activity. These observations show for the first time that patients with fluorosis have markedly elevated osteocalcin, a marker of osteoblastic activity, and that they may have significantly elevated PTH concentrations in the presence of normal total and ionized calcium concentrations.

Potential human developmental toxicants and the role of animal testing in their identification and characterization

Some 50 chemicals have been identified from environmental, occupational, or therapeutic exposure data as being potential developmental toxicants in humans. The toxicity pattern of these chemicals in humans has been characterized and correlated with developmental toxicity end points in laboratory animal models in order to determine the relevance and predictiveness of the results of testing in animals in extrapolation to human data. In general, animal developmental toxicity data closely paralleled human outcomes, and while humans in most cases were more sensitive than animals, the data support the concept that, imperfections aside, studies in animals serve a vital role in the hazard identification process.

Maternal toxicity of drugs and metabolic disorders--a possible etiologic factor in the intrauterine death and congenital malformation: a critique on human data

Human data were searched to determine whether an association of metabolically or drug-induced maternal toxicity with congenital malformations and intrauterine death would be valid for the human species. Intrauterine death was found to occur in association with maternal homeostatic alterations resulting from phenylketonuria and diabetes, and with maternal toxicity from toxemia of pregnancy, leukemia, burns, alcohol, aminopterin, isotretinoin, and possibly trimethadione. A pattern of anomalies found similar (except for minor differences) and thus suggestive of a possible common cause, was observed among anomalies to phenylketonuria, diabetes mellitus, aminopterin, alcohol, warfarin, phenytoin, phenobarbital, trimethadione, valproic acid, and isotretinoin. The pattern usually consisted of deficiencies in pre- and postnatal development, mid-facial hypoplasia, cleft palate, atrial or ventricular septal defects, patent ductus arteriosus, hypospadias, hernias, and other less frequent anomalies. The pattern is tentatively associated with alterations in maternal physiology resulting from phenylketonuria and diabetes; maternal toxicity of aminopterin, alcohol, and diverse factors co-occurring with warfarin use; and therapeutic doses (generally toxic in adults) of phenytoin, phenobarbital, trimethadione, and valproic acid. Whether these fetal malformations and intrauterine deaths would occur at nonmaterno-toxic levels of the above teratogenic agents, and, consequently, the strength of the associations could not be estimated for lack of data. However, human data seem to provide some, though weak, support and not to contradict the previous assumption formulated from animal studies that maternal toxicity may be causally related to fetal malformations and embryo-fetal mortality.

Antithrombotic therapy in patients with valvular heart disease and prosthetic heart valves

Indications and the type of antithrombotic therapy for the prevention of thromboembolism in patients with valvular heart disease, mechanical prosthetic heart valves and bioprosthetic heart valves are discussed. The evidence for these clinical recommendations is described and graded into five levels. The indications for anticoagulation in patients with valvular heart disease are chronic or paroxysmal atrial fibrillation, sinus rhythm with a very large left atrium, severe left ventricular dysfunction or presence of heart failure or a history of previous thromboembolism. Anticoagulant therapy is administered to prolong the prothrombin time to 1.5 to 2.0 times control, using rabbit brain thromboplastin (standardized international normalized ratio = 3.0 to 4.5). Risk factors for thromboembolism in patients with prosthetic heart valves are discussed. Because intracardiac thrombus formation may start during and continues early after operation, restarting heparin therapy 6 hours after operation and continuing it for the duration of the hospitalization is advised. For mechanical prosthetic heart valves, oral anticoagulation as outlined plus dipyridamole is advised indefinitely. Platelet inhibitor therapy alone is insufficient. For bioprosthetic heart valves, heparin is followed by oral anticoagulation as outlined for 3 months after mitral or aortic valve replacement and indefinitely after mitral valve replacement if there is atrial fibrillation or a very large left atrium; aspirin may be recommended indefinitely after aortic valve replacement. Antithrombotic therapy is also considered for four special situations: noncardiac surgery, prosthetic valve endocarditis, anticoagulation after a thromboembolic event, and antithrombotic therapy during pregnancy.

The congenital warfarin syndrome

A rare congenital nasal deformity due to warfarin embryopathy is reported. The commonest anomalies described in this syndrome are: hypoplasia of the nose, stippling of bone, optic atrophy and mental retardation. The various abnormalities and the mechanism of warfarin teratogenesis are discussed.

Cardiac valve prostheses, anticoagulation, and pregnancy

The course of 76 pregnancies is reported in 51 women who became pregnant after replacement of one or more heart valves. Age at conception ranged from 17 to 39 years (mean 25). There have been 71 deliveries and five women are still pregnant at the time of writing. In the 71 pregnancies, oral anticoagulants were given during 53, heparin during five, and no anticoagulants during 13. Fetal complications consisted of 12 spontaneous abortions (eight in pregnancies in which oral anticoagulants were given, three in which heparin was given, and one in which no anticoagulants were given), of 12 premature deliveries with seven stillbirths (three on oral anticoagulants and four without anticoagulants), and there were three neonatal deaths (in all all three instances oral anticoagulants had been given during pregnancy). The maternal complications were as follows. Two women with mitral valve prostheses on heparin had thromboembolic episodes. Four women on oral anticoagulants died and 11 developed haemorrhage or systemic embolism. Two of the deaths were caused by bacterial endocarditis, one was the result of obstruction of a mitral valve prosthesis, and one was due to haemorrhage. One patient developed pulmonary oedema during delivery which rapidly resolved. Seven patients had uterine bleeding after delivery (three of them were on heparin and one was on an antiplatelet agent).

Pregnancy and cardiac valvular prostheses

Many women who have had cardiac valve replacements have reached or will soon be reaching childbearing age. Pregnancy exposes these women to potential problems resulting from the previous valvuloplasty. The three most common problems in this population--thromboembolism, infective endocarditis, and myocardial decompensation are discussed through a review of current literature. Preventive measures and treatment modalities are presented in order to assist nurses caring for these clients during their pregnancy.