Serial examination of 20,248 newborn fetuses and infants: correlations between drug exposure and major malformations

The risk of congenital heart defects associated with corticosteroids use during the first trimester of pregnancy: a systematic review and meta-analysis

BACKGROUND

Prior studies have suggested that maternal corticosteroids exposure during the first trimester may be associated with an increased risk of congenital heart defects (CHDs) in offspring. However, the findings are discrepant. Moreover, a complete overview of the existing data in the literature is lacking. Our objective was to identify whether such an association exists.

METHODS AND RESULTS

Relevant studies were identified via searching PubMed, Web of Science, Embase, Chinese databases, and the Cochrane Library databases (search date July 15, 2021) and through checking the reference lists of retrieved articles. The overall pooled risk estimate was calculated using random-effect models. We used the GRADE approach to assess the overall strength of the evidence and the Newcastle-Ottawa Scale to assess study quality. Subgroup analyses were performed to evaluate the association within studies or samples with different characteristics. Sensitivity analyses were performed to assess the robustness of the results. Nine studies involving 1,901,599 participants were included in the final analysis. All studies were evaluated as high quality. In the meta-analysis, no statistically significant association was found between maternal corticosteroids exposure during the first trimester and increased risk of CHDs in offspring (OR = 1.06, 95% CI: 1.00-1.13, P = 0.06, low certainty of evidence). Additionally, we also did not find significant differences in subgroup analyses of corticosteroids exposure patterns, including oral corticosteroids exposure (OR = 1.23, 95% CI: 1.00-1.52), ointment corticosteroids exposure (OR = 1.03, 95% CI: 0.90-1.19), inhalation corticosteroids exposure (OR = 1.06, 95% CI: 0.96-1.17), topical corticosteroids or systemic corticosteroids exposure (OR = 0.95, 95% CI: 0.79-1.15), and nasal corticosteroids exposure (OR = 1.12, 95% CI: 0.80-1.57).

CONCLUSIONS

Our study does not find an association between maternal corticosteroids exposure during the first trimester and offspring CHDs. However, the existing evidence is of low quality; thus, long-term prospective cohort studies are warranted to verify the safety of corticosteroids in this population, with adequate adjustments for confounding variables.

Risk of congenital malformations in offspring of women using β-blockers during early pregnancy: An updated meta-analysis of observational studies

AIMS

Beta-blockers are commonly used to treat hypertension that arises during pregnancy. However, reproductive safety concerns have been expressed. Here, we investigated whether the use of β-blockers during early pregnancy increased the risk of congenital malformations.

METHODS

A systematic literature search was performed in PubMed, Embase and Cochrane Library to identify relevant studies published from database inception until February 2020. Observational studies evaluating associations between maternal β-blocker use and congenital malformations were included in this meta-analysis. Two reviewers independently extracted data and assessed study quality. Meta-analysis of outcomes was performed and a summary odds ratio (OR) was calculated with consideration of heterogeneity.

RESULTS

Twenty observational studies were identified. Beta-blocker use during early pregnancy was not associated with an increased risk of congenital malformations (OR = 1.01, 95% confidence interval [CI] = 0.93-1.09). Subgroup analysis of organ-specific malformations revealed that β-blocker use was associated with an increased risk of heart malformations (OR = 1.29, 95% CI = 1.02-1.63) and an increased risk of cleft lip or palate (OR = 1.5, 95% CI = 1.18-1.91); however, these associations (OR = 1.11, 95% CI = 0.94-1.32 for heart malformations; OR = 1.34, 95% CI = 0.98-1.85 for cleft lip or palate) disappeared when the adjusted data were pooled. Beta-blocker use was not associated with increased risks of central nervous system malformations, neural tube defects or hypospadias.

CONCLUSION

Exposure to β-blockers during early pregnancy does not appear to be associated with congenital malformations or heart malformations in offspring. Other organ-specific congenital malformations should be evaluated in further studies.

Advances in Epidemiological Methods and Utilisation of Large Databases: A Methodological Review of Observational Studies on Central Nervous System Drug Use in Pregnancy and Central Nervous System Outcomes in Children

INTRODUCTION

Studies have used various epidemiological approaches to study associations between central nervous system (CNS) drug use in pregnancy and CNS outcomes in children. Studies have generally focused on clinical adverse effects, whereas variations in methodologies have not received sufficient attention.

OBJECTIVE

Our objective was to review the methodological characteristics of existing studies to identify any limitations and recommend further research.

METHODS

A systematic literature search was conducted on observational studies listed in PubMed from 1 January 1946 to 21 September 2017. Following independent screening and data extraction, we conducted a review addressing the trends of relevant studies, differences between various data sources, and methods used to address bias and confounders; we also conducted statistical analyses.

RESULTS

In total, 111 observational studies, 25 case-control studies, and 86 cohort studies were included in the review. Publications dating from 1978 to 2006 mainly focused on antiepileptic drugs, but research on antidepressants increased from 2007 onwards. Only one study focused on antipsychotic use during pregnancy. A total of 46 studies obtained data from an administrative database/registry, 20 from ad hoc disease registries, and 41 from ad hoc clinical samples. Most studies (58%) adjusted the confounding factors using general adjustment, whereas only a few studies used advanced methods such as sibling-matched models and propensity score methods; 42 articles used univariate analyses and 69 conducted multivariable regression analyses.

CONCLUSION

Multiple factors, including different study designs and data sources, have led to inconsistent findings in associations between CNS drug use in pregnancy and CNS outcomes in children. Researchers should allow for study designs with clearly defined exposure periods, at the very least in trimesters, and use advanced confounding adjustment methodology to increase the accuracy of the findings.

Safety of Amlodipine in Early Pregnancy

Background

Amlodipine is used for the treatment of hypertension, but reports on its use in early pregnancy are limited.

Methods and Results

In the present study, we recruited 231 women with chronic hypertension, including those who received amlodipine or other antihypertensives during early pregnancy, and investigated frequencies of morphologic abnormalities in their 231 offspring. Specifically, we evaluated 48 neonates exposed to amlodipine in the first trimester (amlodipine group, Group A), 54 neonates exposed to antihypertensives other than amlodipine (other antihypertensive group, Group O), and 129 neonates not exposed to antihypertensives (no‐antihypertensive group, Group N). The number of morphologic abnormalities of offspring in each group were 2 in Group A (4.2%; 95% CI, 0.51–14.25); 3 in Group O (5.6%; 95% CI, 1.16–15.39) and 6 in Group N (4.7%; 95% CI, 1.73–9.85). The odds ratio of the primary outcome comparing Group A and Group O was 0.74 (95% CI: 0.118–4.621) and Group A and Group N was 0.89 (95% CI: 0.174–4.575).

Conclusions

The odds of birth defects in Group A in the first trimester were not significantly different from those with or without other antihypertensives.

See Editorial Malha and August

Maternal drug use and the risk of anorectal malformations: systematic review and meta-analysis

Background

Origin of anorectal malformations (ARM) are considered multifactorial. Several genetic and non-genetic risk factors are discussed in literature. Maternal periconceptional medical drug use as possible risk factor, however, has not been reviewed systematically.

Methods

Studies published between 1977 and April 2017 were reviewed through systematic search in PubMed, ISI Web of Knowledge and Scopus databases. Furthermore, related and cross-referencing publications were reviewed. Pooled odds ratios (95% confidence intervals) were determined to quantify associations of maternal periconceptional use of folic acid, multivitamins, anti-asthma medication (separated in any anti-asthma medication, inhaled corticosteroids and salbutamol), thyroid hormone supplements, psychiatric drugs (separated in antidepressants, any selective serotonin reuptake inhibitors [SSRI], sertraline, citalopram, fluoxetine, paroxetine, hypnotics and benzodiazepine) and aspirin with ARM using meta-analyses.

Results

Thirty-seven studies that reported on the association between maternal periconceptional drug intake and infants born with ARM were included in this review. These were conducted in the United States of America (n = 14), Sweden (n = 6), Hungary (n = 5), Germany (n = 3), the Netherlands (n = 3), Denmark (n = 2), France (n = 2), Norway (n = 1) and the UK (n = 1). However, only few of these studies reported on the same risk factors. Studies were heterogeneous with respect to case numbers, period ingestion of medical drug use, control selection and adjustment for covariates. Consistently increased risks were observed for any anti-asthma medication, and hypnotics and benzodiazepine, but not for folic acid, multivitamins, inhaled corticosteroids, salbutamol, thyroid hormone supplements, antidepressants, any SSRI, sertraline, citalopram, fluoxetine, paroxetine and aspirin. In meta-analyses, pooled odds ratios (95% confidence intervals) for any anti-asthma medication, and hypnotics and benzodiazepine were 1.64 (1.22–2.21), and 2.43 (1.03–5.73), respectively.

Conclusion

Evidence on maternal drug use before conception and during pregnancy as risk factor for ARM from epidemiological studies is still very limited. Nevertheless, the few available studies indicate any anti-asthma medication, and hypnotics and benzodiazepine to be associated with increased risks. Further, ideally large-scale multicenter and register-based studies are needed to clarify the role of maternal drug intake for the development of ARM.

Congenital Anomalies in Children of Mothers Taking Antiepileptic Drugs with and without Periconceptional High Dose Folic Acid Use: A Population-Based Cohort Study

Background

Antenatal antiepileptic drug (AED) use has been found to be associated with increased major congenital anomaly (CA) risks. However whether such AED-associated risks were different according to periconceptional high dose (5mg daily) folic acid supplementation is still unclear.

Methods

We included 258,591 singleton live-born children of mothers aged 15-44 years in 1990-2013 from The Health Improvement Network, a large UK primary care database. We identified all major CAs according to the European Surveillance of Congenital Anomalies classification. Absolute risks and adjusted odds ratios (aOR) were calculated comparing children of mothers prescribed AEDs to those without such prescriptions, stratified by folic acid prescriptions around the time of conception (one month before conception to two months post-conception).

Results

CA risk was 476/10,000 in children of mothers with first trimester AEDs compared with 269/10,000 in those without AEDs equating to an aOR of 1.82, 95% confidence interval 1.30-2.56. The highest system-specific risks were for heart anomalies (198/10,000 and 79/10,000 respectively, aOR 2.49,1.47-4.21). Sodium valproate and lamotrigine were both associated with increased risks of any CA (aOR 2.63,1.46-4.74 and aOR 2.01,1.12-3.59 respectively) and system-specific risks. Stratification by folic acid supplementation did not show marked reductions in AED-associated risks (e.g. for CAs overall aOR 1.75, 1.01-3.03 in the high dose folic acid group and 1.94, 95%CI 1.21-3.13 in the low dose or no folic acid group); however, the majority of mothers taking AEDs only initiated high dose folic acid from the second month of pregnancy.

Conclusions

Children of mothers with AEDs in the first trimester of pregnancy have a 2-fold increased risk of major CA compared to those unexposed. We found no evidence that prescribed high dose folic acid supplementation reduced such AED-associated risks. Although statistical power was limited, prescribing of folic acid too late for it to be effective during the organogenic period or selective prescribing to those with more severe morbidity may explain these findings.

Early pregnancy exposure to antihistamines and risk of congenital heart defects: results of two case-control studies

We aimed to study the association between use of antihistamines in early pregnancy and congenital heart defects (CHD) in the offspring.

DESIGN

Two case-control studies.

SETTING

HAVEN study, Erasmus MC, University Medical Centre, Rotterdam, and Eurocat Northern Netherlands (NNL), University Medical Center Groningen, Groningen, the Netherlands. We studied 361 children with CHD and 410 controls without congenital malformations from the HAVEN study and replicated the analyses in 445 children with CHD and 530 controls from the Eurocat NNL registry. Information about antihistamine use in early pregnancy and potential confounders was obtained from questionnaires postpartum. We calculated the association between antihistamines and CHD risk by multivariable logistic regression analysis.

MAIN OUTCOME MEASURES

Odds ratios (OR) with 95% confidence intervals (CI). In the HAVEN study, 25 of 771 mothers used antihistamines that were associated with an increased CHD risk (OR 3.0, 95% CI 1.2-7.3), particularly atrioventricular septal defects (AVSD) (OR 5.1, 95 % CI 1.3-20.5) and perimembranous ventricular septal defects (pVSD) (OR 5.1, 95% CI 1.8-14.4). Mothers with severe nausea who did not use antihistamines had a reduced risk (OR 0.7, 95% CI 0.5-0.98), whereas nauseous mothers using antihistamines showed an almost fivefold increased risk of pVSD (OR 4.8, 95% CI 1.1-21.8). The association between antihistamines and AVSD was confirmed in the Eurocat cohort (OR 3.5, 95% CI 1.4-8.7), but we could not replicate the association with overall CHD risk. We found a positive association between antihistamine use in early pregnancy and CHD risk, particularly AVSD, which seemed to be independent of nausea/vomiting.

The risk of congenital malformations associated with exposure to β-blockers early in pregnancy: a meta-analysis

β-blockers are commonly used during the first trimester of pregnancy. Data about risks of congenital anomalies in offspring have not been summarized. We performed a meta-analysis to determine teratogenicity of β-blockers in early pregnancy. A systematic literature search was performed using PubMed, EMBASE, Cochrane Clinical Trials, and hand search. Meta-analyses were performed using random-effects models based on odds ratios (ORs). Prespecified subgroup analyses were performed to explore heterogeneity. Randomized controlled trials or observational studies examining risks of congenital malformations associated with first trimester β-blocker exposure compared with no exposure were included. Thirteen population-based case-control or cohort studies were identified. Based on meta-analyses, first-trimester oral β-blocker use showed no increased odds of all or major congenital anomalies (OR=1.00; 95% confidence interval, 0.91-1.10; 5 studies). However, in analyses examining organ-specific malformations, increased odds of cardiovascular defects (OR=2.01; 95% confidence interval, 1.18-3.42; 4 studies), cleft lip/palate (OR=3.11; 95% confidence interval, 1.79-5.43; 2 studies), and neural tube defects (OR=3.56; 95% confidence interval, 1.19-10.67; 2 studies) were observed. The effects on severe hypospadias were nonsignificant (1 study). Causality is difficult to interpret given the small number of heterogeneous studies and possibility of biases. Given the frequency of this exposure in pregnancy, further research is needed.

The effect of using the health smart card vs. CPOE reminder system on the prescribing practices of non-obstetric physicians during outpatient visits for pregnant women in Taiwan

INTRODUCTION

There is an evidence that pregnant women have been prescribed a significant number of improper medications that could lead to potential damage for a developing fetus due to discontinuity of care. The safety of pregnant women raises public concern and there is a need to identify ways to prevent potential adverse events to the pregnant woman. This study used a health smart card with a clinical reminder system to keep continuous records of general outpatient visits of pregnant women to protect them from potential adverse events caused by improper prescription.

METHOD

The health smart card, issued to all 23 million citizens in Taiwan, was used to work with a Computerized Physician Order Entry (CPOE) implemented at a 700-bed teaching medical center in Taipei to provide the outpatient information of pregnant women. FDA pregnancy risk classification was used to categorize the risk of pregnant women. The log file, combined with the physicians' and patients' profiles, were statistically examined using the Mantel-Haenszel technique to evaluate the impact of system in changing physician's prescription behavior.

RESULTS

A total of 441 patients ranged in age from 15 to 50 years with 1114 prescriptions involved in FDA pregnancy risk classification C, D, and X during the study period. 144 reminders (13.1%) were accepted by physicians for further assessment and 100 (69.4%) of them were modified. Non-obstetric physicians in non-emergency setting were more intended to accept reminders (27.8%, 4.9 folds than obstetricians). Reminders triggered on patients in second trimester (15.5%) were accepted by all physicians more than third trimester (OR 1.52, p<0.05).

CONCLUSION

A health smart card armed with CPOE reminder system and well-defined criteria had the potential to decrease harmful medication prescribed to pregnant patients. The results show better conformance for non-obstetric physicians (26%) and when physicians accepted the alerts they are more likely to went back and review their orders (69%). In sum, reminder criteria of FDA pregnancy risk classification C for obstetricians and reminder based on different trimesters is suggested to be refined to improve system acceptability and to decrease improper prescription.

Maternal thyroid disease, thyroid medication use, and selected birth defects in the National Birth Defects Prevention Study

BACKGROUND

Although thyroid disorders are present in approximately 3% of pregnant women, little is known about the association between maternal thyroid disease and birth defects.

METHODS

We assessed the association between maternal thyroid disease, thyroid medication use, and 38 types of birth defects among 14,067 cases and 5875 controls in the National Birth Defects Prevention Study, a multisite, population-based, case-control study. Infants in this study were born between October 1997 and December 2004. Information on exposures including maternal diseases and use of medications was collected by telephone interview.

RESULTS

We found statistically significant associations between maternal thyroid disease and left ventricular outflow tract obstruction heart defects (1.5; 95% CI, 1.0-2.3), hydrocephaly (2.9; 95% CI, 1.6-5.2), hypospadias (1.6; 95% CI, 1.0-2.5), and isolated anorectal atresia (2.4; 95% CI, 1.2-4.6). Estimates for the association between periconceptional use of thyroxine and specific types of birth defects were similar to estimates for any thyroid disease. Given that antithyroid medication use was rare, we could not adequately assess risks for their use for most case groups.

CONCLUSIONS

Our results are consistent with the positive associations between maternal thyroid disease or thyroid medication use and both hydrocephaly and hypospadias observed in some previous studies. New associations with left ventricular outflow tract obstruction heart defects and anorectal atresia may be chance findings.

The potential of the European network of congenital anomaly registers (EUROCAT) for drug safety surveillance: a descriptive study

BACKGROUND

European Surveillance of Congenital Anomalies (EUROCAT) is a network of population-based congenital anomaly registries in Europe surveying more than 1 million births per year, or 25% of the births in the European Union. This paper describes the potential of the EUROCAT collaboration for pharmacoepidemiology and drug safety surveillance.

METHODS

The 34 full members and 6 associate members of the EUROCAT network were sent a questionnaire about their data sources on drug exposure and on drug coding. Available data on drug exposure during the first trimester available in the central EUROCAT database for the years 1996-2000 was summarised for 15 out of 25 responding full members.

RESULTS

Of the 40 registries, 29 returned questionnaires (25 full and 4 associate members). Four of these registries do not collect data on maternal drug use. Of the full members, 15 registries use the EUROCAT drug code, 4 use the international ATC drug code, 3 registries use another coding system and 7 use a combination of these coding systems. Obstetric records are the most frequently used sources of drug information for the registries, followed by interviews with the mother. Only one registry uses pharmacy data. Percentages of cases with drug exposure (excluding vitamins/minerals) varied from 4.4% to 26.0% among different registries. The categories of drugs recorded varied widely between registries.

CONCLUSIONS

Practices vary widely between registries regarding recording drug exposure information. EUROCAT has the potential to be an effective collaborative framework to contribute to post-marketing drug surveillance in relation to teratogenic effects, but work is needed to implement ATC drug coding more widely, and to diversify the sources of information used to determine drug exposure in each registry.

Outcome of pregnancy in a randomized controlled study of patients with asthma exposed to budesonide

BACKGROUND

Budesonide is the only inhaled corticosteroid to be given a category B pregnancy rating by the US Food and Drug Administration, based on observational data from the Swedish Medical Birth Registry. However, data from large randomized controlled trials are lacking.

OBJECTIVE

To compare pregnancy outcomes among patients with recent-onset mild-to-moderate persistent asthma receiving low-dose budesonide vs placebo.

METHODS

In a randomized, double-blind, placebo-controlled trial, 7241 patients aged 5 to 66 years with mild-to-moderate persistent asthma for less than 2 years and no previous regular corticosteroid therapy received once-daily budesonide or placebo via dry powder inhaler in addition to their usual asthma medication for 3 years. This trial was followed by a 2-year open-label treatment period. The daily dose of budesonide was 400 microg for adults. The study included 2473 females aged 15 to 50 years at randomization. Pregnancy was not an exclusion criterion (except for U.S. patients).

RESULTS

Of 319 pregnancies reported, 313 were analyzed. Healthy children were delivered in 81% and 77% of all pregnancies in the budesonide and placebo groups, respectively. Of the 196 pregnancies reported by participants taking budesonide, 38 (19%) had adverse outcomes: 23 (12%) had miscarriages, 3 (2%) had congenital malformations, and 12 (6%) had other outcomes. Of the 117 pregnancies reported in the placebo group, 27 (23%) had adverse outcomes: 11 (9%) had miscarriages, 4 (3%) had congenital malformations, and 12 (10%) had other outcomes.

CONCLUSIONS

Treatment with low-dose inhaled budesonide in females with mild-to-moderate persistent asthma does not seem to affect the outcome of pregnancy.

Imbalances emerge in cardiac autonomic cell signaling after neonatal exposure to terbutaline or chlorpyrifos, alone or in combination

During early neonatal development, the future reactivity of the heart to cardiac autonomic stimulation is programmed by the timing and intensity of the arrival of parasympathetic and sympathetic inputs. In neonatal rats, we examined the effects of exposure to terbutaline, a beta-adrenoceptor (betaAR) agonist used to arrest preterm labor, and chlorpyrifos (CPF), a widely used organophosphate pesticide that acts in part through inhibition of cholinesterase, using scenarios mimicking the likely developmental stages corresponding to peak human exposures: postnatal days (PN) 2-5 for terbutaline and PN11-14 for CPF. Terbutaline evoked a progressive deficit in cardiac betaAR binding but did not interfere with the ability of the receptors to stimulate adenylyl cyclase (AC). Terbutaline also reduced expression of m2 muscarinic acetylcholine receptors and suppressed their ability to inhibit AC. Surprisingly, CPF produced similar actions, a decrement in betaAR and m2 muscarinic receptor binding and a loss of the cholinergic AC response, and also augmented the ability of betaARs to stimulate AC. The effects of CPF are thus unlikely to reside in cholinergic hyperstimulation resulting from cholinesterase inhibition but instead involve other actions converging on receptors and cell signaling. Exposure to both agents, terbutaline followed by CPF, produced a summation of the two individual effects. Our findings at the level of cell signaling thus indicate that neonatal exposure to terbutaline or CPF, or sequentially to both agents, results in an imbalance of cardiac autonomic inputs favoring increased excitability, an outcome that may have an impact on cardiovascular responses.

Developmental exposure to terbutaline alters cell signaling in mature rat brain regions and augments the effects of subsequent neonatal exposure to the organophosphorus insecticide chlorpyrifos

Exposure to apparently unrelated neurotoxicants can nevertheless converge on common neurodevelopmental events. We examined the long-term effects of developmental exposure of rats to terbutaline, a beta-adrenoceptor agonist used to arrest preterm labor, and the organophosphorus insecticide chlorpyrifos (CPF) separately and together. Treatments mimicked the appropriate neurodevelopmental stages for human exposures: terbutaline on postnatal days (PN) 2-5 and CPF on PN11-14, with assessments conducted on PN45. Although neither treatment affected growth or viability, each elicited alterations in CNS cell signaling mediated by adenylyl cyclase (AC), a transduction pathway shared by numerous neuronal and hormonal signals. Terbutaline altered signaling in the brainstem and cerebellum, with gender differences particularly notable in the cerebellum (enhanced AC in males, suppressed in females). By itself, CPF exposure elicited deficits in AC signaling in the midbrain, brainstem, and striatum. However, sequential exposure to terbutaline followed by CPF produced larger alterations and involved a wider spectrum of brain regions than were obtained with either agent alone. In the cerebral cortex, adverse effects of the combined treatment intensified between PN45 and PN60, suggesting that exposures alter the long-term program for development of synaptic communication, leading to alterations in AC signaling that emerge even after adolescence. These findings indicate that terbutaline, like CPF, is a developmental neurotoxicant, and reinforce the idea that its use in preterm labor may create a subpopulation that is sensitized to long-term CNS effects of organophosphorus insecticides.

Does pharmacotherapy for preterm labor sensitize the developing brain to environmental neurotoxicants? Cellular and synaptic effects of sequential exposure to terbutaline and chlorpyrifos in neonatal rats

It is increasingly clear that environmental toxicants target specific human subpopulations. In the current study, we examined the effects of prior developmental exposure to a beta(2)-adrenoceptor agonist used to arrest preterm labor, terbutaline, on the subsequent effects of exposure to the organophosphate insecticide, chlorpyrifos (CPF). Neonatal rats were given terbutaline on postnatal day (PN) 2-5, followed by CPF on PN11-14. Although neither treatment affected growth or viability, each elicited alterations in indices of brain cell differentiation and cholinergic innervation in the immediate posttreatment period (PN15), persisting into adulthood (PN60). Biomarkers of brain cell number (DNA concentration and content), cell size (protein/DNA ratio) and neuritic projections (membrane/total protein) were affected by either agent alone, with patterns consistent with neuronal and neuritic damage accompanied by reactive gliosis. The combined exposure augmented these effects by both additive and synergistic mechanisms. Similarly, choline acetyltransferase (ChAT), a constitutive marker for cholinergic nerve terminals, was affected only by combined exposure to both terbutaline and CPF. Indices of cholinergic synaptic activity [hemicholinium-3 and m(2)-muscarinic acetylcholine receptor binding] showed impairment after exposure to either terbutaline or CPF but the effects were more severe when the treatments were combined. These findings suggest that terbutaline, like CPF, is a developmental neurotoxicant, and that its use in the therapy of preterm labor may create a subpopulation that is sensitized to the adverse neural effects of a subsequent exposure to organophosphate insecticides.

β-Adrenoceptor modulation of transiently overexpressed α2-adrenoceptors in brain and peripheral tissues: cellular mechanisms underlying the developmental toxicity of terbutaline

Terbutaline, a selective beta(2)-adrenoceptor (beta(2)AR) agonist, is widely used as a tocolytic to arrest preterm labor but recent studies indicate that excessive betaAR stimulation can alter the expression and function of other neurotransmitter receptors that are essential to fetal/neonatal development. In many immature tissues, alpha(2)-adrenergic receptors (alpha(2)ARs) are overexpressed and the receptors are thought to play a role in cell proliferation and architectural assembly. We evaluated whether betaAR agonists perturb the expression of alpha(2)ARs in central and peripheral tissues during various developmental stages in the fetal and neonatal rat. In peripheral tissues (heart, liver, kidney) administration of terbutaline (10mg/kg s.c. for 4 days) elicited decrements in alpha(2)AR expression only during a critical developmental window that differed for each tissue; terbutaline was more effective than isoproterenol, a mixed beta(1)/beta(2) agonist. Neonatal destruction of sympathetic nerves with 6-hydroxydopamine (6-OHDA) had a biphasic effect, initially reducing alpha(2)ARs but subsequently elevating receptor expression. In contrast to the effects in the periphery, terbutaline administration promoted alpha(2)AR expression in neonatal brain regions with effects preferential to males. As the rat is an altricial species, these results during late gestation and the early neonatal period indicate that betaAR input modulates alpha(2)AR expression during developmental stages in which betaAR tocolytics are likely to be used. Disruption of alpha(2)AR expression and function may therefore contribute to adverse effects that have been noted in the offspring of pregnant women treated with terbutaline.

Does terbutaline damage the developing heart?

BACKGROUND

Beta(2)-Adrenoceptor (betaAR) agonists, such as terbutaline, are widely used to arrest preterm labor. They also cross the placenta where they stimulate receptors in fetal tissues, which in turn use betaAR input for trophic control of cell replication and differentiation.

METHODS

As rats are altricial, we administered terbutaline in two different postnatal exposure periods (10 mg/kg given daily on Days 2-5 or 11-14).

RESULTS

Hearts were examined twenty-four hours after the last dose and on postnatal day 30 for cardiac damage. Neither treatment paradigm caused an increase in cardiac abnormalities compared to controls but quantitative analysis of the number of nuclei indicated reductions in females.

CONCLUSIONS

These findings do not support earlier case reports of outright myocardial necrosis after terbutaline tocolysis in human infants. Nevertheless, the significant statistical association between terbutaline and cardiac anomalies in epidemiological studies suggest that terbutaline may sensitize the developing heart to other insults that affect development.

Developmental toxicity of terbutaline: critical periods for sex-selective effects on macromolecules and DNA synthesis in rat brain, heart, and liver

beta-Adrenoceptors (betaARs) control cell replication/differentiation, and during development, signaling is not subject to desensitization. We examined the effects of terbutaline, a beta(2)AR agonist used as a tocolytic, on development in rat brain regions and peripheral tissues with high betaAR concentrations. Prenatal terbutaline (gestational days 17-20) decreased cell numbers (DNA content) in the fetal brain and liver. Early postnatal exposure (PN2-5) reduced DNA synthesis in early-developing brain regions of females, with sensitization of the effect upon repeated terbutaline administration; after multiple terbutaline injections, DNA content was reduced in male cerebellum. The cerebellum was targeted later (PN11-14), exhibiting decreased DNA synthesis in both sexes; in contrast, cardiac DNA synthesis decreased after one injection but increased after the fourth daily injection. Our results suggest that excessive betaAR stimulation by terbutaline alters cell development in brain regions and peripheral tissues, with the net effect depending on sex and the timing of exposure. These effects may contribute to neuropsychiatric, cognitive, cardiovascular, and metabolic abnormalities reported in the offspring of women treated with beta-agonist tocolytics.

Beta-adrenoceptor control of G protein function in the neonate: determinant of desensitization or sensitization

Neonatal beta-adrenoceptors (beta-ARs) are resistant to agonist-induced desensitization. We examined the functioning of G(i) and G(s) after repeated administration of beta-AR agonists to newborn rats. Isoproterenol (beta(1)/beta(2) agonist) obtunded G(i) function in the heart but not the liver; in contrast, terbutaline, a beta(2)-selective agonist, enhanced G(i) function. Isoproterenol, but not terbutaline, increased membrane-associated G((s)alpha), which would enhance receptor function. In addition, isoproterenol increased and terbutaline maintained the proportion of the short-splice (S) variant of G((s)alpha) in the membrane fraction; G((s)alpha)S is functionally more active than the long-splice variant. Either isoproterenol or terbutaline treatment increased G((s)alpha) in the cytosolic fraction, a characteristic usually associated with desensitization in the adult. Decreased G(i) activity, coupled with increased membrane-associated G((s)alpha) concentrations and maintenance or increases in membrane G((s)alpha)S, provide strong evidence that unique effects on G protein function underlie the ability of the immature organism to sustain beta-AR cell signaling in the face of excessive or prolonged stimulation; these mechanisms also contribute to tissue selectivity of the effects of beta-agonists with divergent potencies toward different beta-AR subtypes.

Are developing beta-adrenoceptors able to desensitize? Acute and chronic effects of beta-agonists in neonatal heart and liver

During fetal and neonatal development, beta-adrenergic receptors (beta-ARs) appear to be resistant to desensitization by beta-agonist drugs. To determine the mechanisms underlying the regulatory differences between adults and neonates, we administered isoproterenol, a mixed beta(1)/beta(2)-AR agonist, and terbutaline, a beta(2)-selective agonist. Effects were examined in the ensuing 4 h after a single injection, or after the last of four daily injections. We prepared cell membranes from heart (predominantly beta(1)-ARs) and liver (predominantly beta(2)-ARs) and assessed signal transduction in the adenylyl cyclase (AC) pathway. In the first few hours after a single administration of isoproterenol to adult rats, cardiac beta-ARs showed activation of G proteins (elevated AC response to forskolin) and desensitization of beta-AR-mediated responses; after the fourth injection, heterologous desensitization emerged, characterized by a loss of signaling mediated either through beta-ARs or glucagon receptors. Terbutaline evoked an increase in the forskolin response but no desensitization of receptor-mediated responses. When we gave the same treatments to neonatal rats, we observed cardiac G protein activation, but there was neither homologous nor heterologous desensitization of beta-ARs or glucagon receptors. In the adult liver, isoproterenol and terbutaline both failed to evoke desensitization, regardless of whether the drugs were given once or for 4 days. In neonates, however, acute or chronic treatment elicited homologous desensitization of beta-AR-mediated AC signaling, while sensitizing the response to glucagon. These results show that neonatal beta-ARs are inherently capable of desensitization in some, but not all, cell types; cellular responses can be maintained through heterologous sensitization of signaling proteins downstream from the receptor. Differences from adult patterns of response are highly tissue selective and are likely to depend on ontogenetic differences in subtypes of beta-ARs and AC.

Beta-adrenoceptor-mediated cell signaling in the neonatal heart and liver: responses to terbutaline

Terbutaline, a beta(2)-adrenoceptor (beta(2)-AR) agonist, is a widely used tocolytic that also crosses the placenta to stimulate fetal beta-ARs. The current study examines the effects of terbutaline administered to neonatal rats. Terbutaline (10 mg/kg sc) given on postnatal day (PN) 2-5 or PN 11-14 elicited significant downregulation of both cardiac and hepatic beta-ARs, with a much greater effect in the liver. Despite the reduction in cardiac beta-ARs, receptor desensitization was absent as evidenced by the maintained ability of isoproterenol to stimulate adenylyl cyclase (AC) in membrane preparations. The underlying mechanism was dissected by using stimulants that operate at different points in the AC signaling pathway, NaF, forskolin, and Mn(2+). When administered in the early neonatal period, terbutaline failed to evoke any changes in cardiac AC activity; however, treatment on PN 11-14 evoked heterologous sensitization downstream from the receptor, evidenced by increases in the response to NaF and forskolin. In the liver, neonatal terbutaline administration elicited a small (approximately equal to 10%) decrease in the AC response to isoproterenol, an effect much smaller than the downregulation of beta-ARs (>40%). In this tissue, desensitization was again offset by heterologous sensitization of AC signaling. These results indicate that, in the developing organism, beta-AR-mediated cell signaling responses are maintained in the face of receptor downregulation through heterologous induction of downstream signaling elements. These unique responses serve to sustain beta-AR signaling in the perinatal period.

Beta-adrenoceptor signaling in the developing brain: sensitization or desensitization in response to terbutaline

Beta(2)-adrenoceptor agonists are commonly used to arrest preterm labor but they also penetrate the placenta to stimulate fetal beta-adrenergic receptors (betaAR), and have been implicated in subsequent neurobehavioral deficits. We administered terbutaline to pregnant rats on gestational days (GD) 17-20 and during two postnatal (PN) periods, PN2-5 and PN11-14, that correspond to third trimester human neurological development. We then examined betaAR binding sites and adenylyl cyclase (AC) signaling in fetal brain or neonatal brain regions. Although fetal terbutaline administration evoked betaAR downregulation, the ability of isoproterenol to stimulate AC was enhanced instead of desensitized. Sensitization occurred at post-receptor signaling proteins, as augmented responses were also seen for stimulants that bypass the receptors to work on G-proteins (NaF) or that stimulate AC directly (forskolin and Mn(2+)). When terbutaline was given on PN2-5, betaAR downregulation was obtained in brainstem, forebrain and cerebellum, but desensitization of the AC response was seen only in the forebrain; the desensitization was heterologous, reflecting decrements in total AC activity rather than specific loss of the betaAR response. With treatment on PN11-14, only the cerebellum showed betaAR downregulation and induction at the level of post-receptor signaling proteins maintained the betaAR-mediated AC response. Our results indicate that, unlike the adult, betaAR signaling in the fetus and neonate is resistant to homologous desensitization by beta-agonists, and in fact, displays heterologous sensitization that sustains or enhances the overall response. The inability to desensitize betaAR responses may lead to disruption of neural cell development as a consequence of tocolytic therapy.

Regulation of fetal cardiac and hepatic beta-adrenoceptors and adenylyl cyclase signaling: terbutaline effects

Terbutaline (Ter), a beta(2)-adrenergic agonist used in preterm labor, stimulates fetal beta-adrenoceptors (beta-ARs). We administered Ter to pregnant rats on gestational days 17-20 and examined beta-ARs and adenylyl cyclase (AC) signaling in heart and liver. Ter produced less downregulation of cardiac beta-ARs than in adults, despite a higher proportion of the beta(2)-subtype, and failed to elicit desensitization of the receptor-mediated AC response. AC stimulants acting at different points indicated an offsetting of homologous desensitization at the level of the beta-AR by heterologous sensitization at the level of AC: induction of total AC catalytic activity and a shift in the catalytic profile or AC isoform. In fetal liver, Ter produced downregulation of beta-ARs, in keeping with the predominance of the beta(2)-subtype; hepatic receptor downregulation was equivalent in fetus and adult. Nevertheless, there was still no desensitization of beta-AR-mediated AC responses and again AC was induced. Our results indicate that, unlike in the adult, fetal beta-AR signaling is not desensitized by beta-agonists and, in fact, displays heterologous sensitization, thus sustaining responses during parturition. At the same time, the inability to desensitize beta-AR AC responses may lead to disruption of cardiac, hepatic, or neural cell development as a consequence of tocolytic therapy with beta-agonists.

Broadsheet number 56: Mechanisms of fetal loss

The most significant task of the pathologist examining a fetal death is, if possible, the provision of an explanation for the event, which will allow the clinical attendants to counsel the family in an informed and relevant manner. In some cases, no adequate explanation will be possible, though many conditions will be excluded and the importance of this exercise is worth emphasising. Often, however, a combination of fetal, maternal or placental conditions can be found and a full or partial explanation offered, and it is the purpose of this broadsheet to highlight some of these conditions and provide suggestions as to sources of further practical help.

Assessing the safety of drugs in pregnancy: the role of prospective cohort studies

Since, for obvious reasons, systematic testing of the teratogenic properties of drugs in humans is not possible in the premarketing phase, the epidemiological approaches to postmarketing risk evaluation are of major importance. Cohort studies, with their prospective exposure assessment, their ability to study even exposure to drugs not commonly used in pregnancy, and their ability to monitor both adverse and beneficial fetal outcomes, seem to be the most promising study type from a methodological viewpoint. Although there are numerous cohort studies on the harmful effects of drug use in pregnant women, only a few have been able to demonstrate a risk in terms of an increase in the prevalence of malformations. Most studies with significant findings were those investigating the risk potential of one group of drugs, the anticonvulsants. The lack of cohort studies showing a risk for drug use in pregnancy, however, is not necessarily indicative of some methodological deficiency. Rather, it may suggest that, for the majority of drugs, their use in pregnancy is not associated with an increased risk of congenital malformations.