Stillbirth Among Women Prescribed Nicotine Replacement Therapy in Pregnancy: Analysis of a Large UK Pregnancy Cohort

Impact of thyroid autoimmunity on pregnancy outcomes in euthyroid patients with recurrent implantation failure

RESEARCH QUESTION

Does thyroid autoimmunity (TAI) adversely affect pregnancy outcomes after IVF/intracytoplasmic sperm injection (ICSI) in euthyroid patients with recurrent implantation failure (RIF)?

DESIGN

This retrospective cohort study was conducted at the Reproductive Hospital Affiliated with Shandong University from November 2016 to September 2021. A total of 1031 euthyroid patients diagnosed with RIF were enrolled. Based on serum thyroid autoantibody concentrations, the participants were divided into two groups: the TAI-positive group (219 women with RIF) and the TAI-negative group (812 women with RIF). The parameters were compared between the two groups. Additionally, logistic regression was used to adjust related confounders for primary outcomes, and subgroup and stratified analyses were performed according to different thyroid autoantibody types and TSH concentrations.

RESULTS

There was no significant difference in ovarian reserve, ovarian response, embryo quality, pregnancy outcome or neonatal outcome between the two groups (P > 0.05). After adjustments for age, body mass index, thyroid-stimulating hormone and free thyroxine, the biochemical pregnancy rate in the TAI-positive group was significantly lower than that in the TAI-negative group (odds ratio 1.394, 95% CI 1.023-1.901, adjusted P = 0.036). Regarding the implantation rate, clinical pregnancy rate, pregnancy loss rate, stillbirth rate and live birth rate, no significant differences were observed even with subgroup and stratified analyses (P > 0.05).

CONCLUSIONS

TAI had no impact on pregnancy outcomes in euthyroid RIF patients who underwent IVF/ICSI. In clinical practice, interventions targeting thyroid autoantibodies in these patients should be implemented with caution and additional evidence is needed.

Nicotine replacement therapy and e-cigarettes in pregnancy and infant respiratory outcomes

BACKGROUND

Nicotine replacement therapy (NRT) and e-cigarettes are recommended to pregnant women who wish to stop smoking. Albeit eliminating other harmful components of cigarettes, those alternatives still expose the developing fetus to nicotine. The lungs may be particularly vulnerable to damage by nicotine as there is widespread nicotinic-acetylcholine receptor expression in the lungs. There is, however, a paucity of information about the effect of NRT and e-cigarette use in pregnancy on infant respiratory outcomes.

AIMS

To explore the effect of NRT and e-cigarettes on the developing lung.

STUDY DESIGN

A literature search was undertaken to examine the use and safety of nicotine-replacement strategies in pregnancy, with a focus on infant respiratory outcomes. This included experimental studies investigating the effect of isolated "gestational" nicotine on the developing lung.

OUTCOME MEASURES

Respiratory outcomes in animal studies and infants.

RESULTS

Animal studies investigating the effect of gestational nicotine exposure on fetal lung development demonstrated abnormal lung growth; including abnormal airway branching and alveolar development. Consequently, offspring display altered pulmonary mechanics, including both increased respiratory rate and airway resistance. These findings mirror respiratory pathology observed in infants born to smoking mothers. Human trials of NRT and e-cigarette use in pregnancy have not identified adverse perinatal outcomes regarding reduced birthweight or prematurity, but have not considered infant and childhood respiratory outcomes.

CONCLUSIONS

Nicotine can impair fetal lung development, leading to concerns regarding the safety of NRT and e-cigarettes in pregnancy. Studies have yet to explore the impact of these nicotine-containing products on infant respiratory outcomes.

Interventions for Tobacco Cessation in Adults, Including Pregnant Persons: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force

IMPORTANCE

It has been estimated that in 2018 nearly 20% of adults in the US were currently using a tobacco product.

OBJECTIVE

To systematically review the effectiveness and safety of pharmacotherapy, behavioral interventions, and electronic cigarettes for tobacco cessation among adults, including pregnant persons, to inform the US Preventive Services Task Force.

DATA SOURCES

PubMed, PsycInfo, Database of Abstracts of Reviews of Effects, Cochrane Database of Systematic Reviews, Centre for Reviews and Dissemination of Health Technology Assessment; surveillance through September 25, 2020.

STUDY SELECTION

Systematic reviews of tobacco cessation interventions and randomized clinical trials that evaluated the effects of electronic cigarettes (e-cigarettes) or pharmacotherapy among pregnant persons.

DATA EXTRACTION AND SYNTHESIS

Independent critical appraisal and data abstraction; qualitative synthesis and random-effects meta-analyses.

MAIN OUTCOMES AND MEASURES

Health outcomes, tobacco cessation at 6 months or more, and adverse events.

RESULTS

Sixty-seven reviews addressing pharmacotherapy and behavioral interventions were included as well as 9 trials (N = 3942) addressing e-cigarettes for smoking cessation and 7 trials (N = 2285) of nicotine replacement therapy (NRT) use in pregnancy. Combined pharmacotherapy and behavioral interventions (pooled risk ratio [RR], 1.83 [95% CI, 1.68-1.98]), NRT (RR, 1.55 [95% CI, 1.49-1.61]), bupropion (RR, 1.64 [95% CI, 1.52-1.77]), varenicline (RR, 2.24 [95% CI, 2.06-2.43]), and behavioral interventions such as advice from clinicians (RR, 1.76 [95% CI, 1.58-1.96]) were all associated with increased quit rates compared with minimal support or placebo at 6 months or longer. None of the drugs were associated with serious adverse events. Five trials (n = 3117) reported inconsistent findings on the effectiveness of electronic cigarettes on smoking cessation at 6 to 12 months among smokers when compared with placebo or NRT, and none suggested higher rates of serious adverse events. Among pregnant persons, behavioral interventions were associated with greater smoking cessation during late pregnancy (RR, 1.35 [95% CI, 1.23-1.48]), compared with no intervention. Rates of validated cessation among pregnant women allocated to NRT compared with placebo were not significantly different (pooled RR, 1.11 [95% CI, 0.79-1.56], n = 2033).

CONCLUSIONS AND RELEVANCE

There is strong evidence that a range of pharmacologic and behavioral interventions, both individually and in combination, are effective in increasing smoking cessation in nonpregnant adults. In pregnancy, behavioral interventions are effective for smoking cessation, but data are limited on the use of pharmacotherapy for smoking cessation. Data on the effectiveness and safety of electronic cigarettes for smoking cessation among adults are also limited and results are inconsistent.

Potential effects of using non-combustible tobacco and nicotine products during pregnancy: a systematic review

Background

The range of risk reduced alternatives to smoking tobacco is increasing and so is use among pregnant women. The substantial harms of smoking during pregnancy are well established and there is reason to believe that nicotine alone is somewhat harmful. Differences in the exposure chemistry strongly suggest that the effects of using smoke-free nicotine products (including pharmaceutical nicotine products, smokeless tobacco, and electronic cigarettes containing nicotine) fall somewhere in the range between zero risk to the risk from smoking. How much lower risk these consumption choices are in terms of pregnancy outcomes, however, remains uncertain.

Methods

We reviewed the literature on smoke-free nicotine and tobacco product exposure and birth-outcome endpoints. Studies were included if they compared outcomes to either no nicotine use or smoking. We searched Google Scholar using broad search terms and additional articles were snowballed from citations. We report what could be learned from each study, given its methods.

Results

Of the 21 studies reviewed, 12 reported on the use of nicotine replacement therapies, 7 on Swedish snus, 1 on Alaskan iq’mik, and 1 on e-cigarettes. The range of results tends to support the prediction that smoke-free product use during pregnancy probably increases the risk of some negative birth outcomes, but that any effect is less than that from smoking. However, the limitations of epidemiology are such that no more-precise a conclusion is possible.

Discussion

The available epidemiology does not change our prior beliefs, based on other evidence and knowledge, that the risks from smoke-free nicotine and tobacco are lower than those for smoking, though it suggests they are non-zero. However, it also demonstrates that the epidemiology is unlikely to provide precise quantitative estimates. This is not just a matter of lack of studies; given the inherent limitation of these studies, doubling or tripling the corpus of available studies would add little precision. For the foreseeable future, decisions about using these products will need to be made based on rough estimates, based on a variety of forms of evidence, and qualitative comparisons.

The Effects of Nicotine on Development

Recently, there has been a significant increase in the use of noncombustible nicotine-containing products, including electronic cigarettes (e-cigarettes). Of increasing popularity are e-cigarettes that can deliver high doses of nicotine over short periods of time. These devices have led to a rise in nicotine addiction in adolescent users who were nonsmokers. Use of noncombustible nicotine products by pregnant mothers is also increasing and can expose the developing fetus to nicotine, a known teratogen. In addition, young children are frequently exposed to secondhand and thirdhand nicotine aerosols generated by e-cigarettes, with little understanding of the effects these exposures can have on health. With the advent of these new nicotine-delivery systems, many concerns have arisen regarding the short- and long-term health effects of nicotine on childhood health during all stages of development. Although health studies on nicotine exposure alone are limited, educating policy makers and health care providers on the potential health effects of noncombustible nicotine is needed because public acceptance of these products has become so widespread. Most studies evaluating the effects of nicotine on health have been undertaken in the context of smoke exposure. Nevertheless, in vitro and in vivo preclinical studies strongly indicate that nicotine exposure alone can adversely affect the nervous, respiratory, immune, and cardiovascular systems, particularly when exposure occurs during critical developmental periods. In this review, we have included both preclinical and clinical studies to identify age-related health effects of nicotine exposure alone, examining the mechanisms underlying these effects.

Electronic cigarettes and obstetric outcomes: a prospective observational study

OBJECTIVE

To compare the obstetric outcomes and socio-demographic factors in electronic cigarette (EC) users with cigarette smokers and non-smokers in pregnancy.

DESIGN

Prospective observational cohort study.

SETTING

A large urban maternity hospital delivering almost 8500 infants per year.

POPULATION

Pregnant women attending for antenatal care.

METHODS

Electronic cigarette users at time of booking history were prospectively identified. Maternal and neonatal outcomes were compared with those of pregnant smokers and non-smokers. Multiple logistic regression analysis was performed to estimate the association between the explanatory variables and birthweight.

MAIN OUTCOMES MEASURES

Infant birthweight, gestation at delivery, incidence of low birthweight.

RESULTS

A total of 218 women with exclusive EC use and 195 women with dual use of both cigarettes and EC, had a live birth during the study period. EC users were of higher socio-economic status than smokers. Infants born to EC users had a mean birthweight of 3470 g (± 555 g), which was similar to that of non-smokers (3471 ± 504 g, P = 0.97) and significantly greater than that of smokers (3166 ± 502 g, P < 0.001). The mean birth centile of EC users was similar to non-smokers (51st centile versus 47th centile, P = 0.28) and significantly greater than that of smokers (27th centile, P < 0.001). Dual users had a mean birthweight and birth centile similar to that of smokers.

CONCLUSION

The birthweight of infants born to EC users is similar to that of non-smokers, and significantly greater than cigarette smokers. Dual users of both cigarettes and EC have a birthweight similar to that of smokers.

TWEETABLE EXTRACT

Birthweight of infants born to electronic cigarette users appears to be similar to that of non-smokers.

Analyzing Missing Data in Perinatal Pharmacoepidemiology Research: Methodological Considerations to Limit the Risk of Bias

Pharmacoepidemiological studies on the safety of medication during pregnancy are all susceptible to missing data (ie, data that should have been recorded but for some reason were not). Missing data are ubiquitous, irrespective of the data source used. Bias can arise when incomplete data on confounders, outcome measures, pregnancy duration, or even cohort selection criteria are used to estimate prenatal exposure effects that would be obtained from the fully observed data, if these were available for each mother-child dyad. This commentary describes general missing data mechanisms and methods, and illustrates how missing data were handled in recent medication in pregnancy research, according to the utilized data source. We further present one applied example on missing data analysis within MoBa (the Norwegian Mother, Father and Child Cohort Study), and finally illustrate how the causal diagram framework can be helpful in assessing risk of bias due to missing data in perinatal pharmacoepidemiology research. We recommend that applied researchers limit missing data during data collection, carefully diagnose missingness, apply strategies for missing data mitigation under different assumptions, and finally include evaluations of robustness results under these assumptions. Following this set of recommendations can aid future perinatal pharmacoepidemiology research in avoiding the problems that result from failure to consider this important source of bias.

Biological effects of nicotine exposure: A narrative review of the scientific literature

The emergence of new tobacco heating products and electronic nicotine delivery systems (ENDS) is changing the way humans are exposed to nicotine. The purpose of this narrative review is to provide a broad overview of published scientific literature with respect to the effects of nicotine on three key health-related areas: 1) cardiovascular risk, 2) carcinogenesis and 3) reproductive outcomes. These areas are known to be particularly vulnerable to the effects of cigarette smoke, and in addition, nicotine has been hypothesized to play a role in disease pathogenesis. Acute toxicity will also be discussed. The literature to February 2019 suggests that there is no increased cardiovascular risk of nicotine exposure in consumers who have no underlying cardiovascular pathology. There is scientific consensus that nicotine is not a direct or complete carcinogen, however, it remains to be established whether it plays some role in human cancer propagation and metastasis. These cancer progression pathways have been proposed in models in vitro and in transgenic rodent lines in vivo but have not been demonstrated in cases of human cancer. Further studies are needed to determine whether nicotine is linked to decreased fertility in humans. The results from animal studies indicate that nicotine has the potential to act across many mechanisms during fetal development. More studies are needed to address questions regarding nicotine exposure in humans, and this may lead to additional guidance concerning new ENDS entering the market.

Cardiovascular, carcinogenic and reproductive effects of nicotine exposure: A narrative review of the scientific literature

The emergence of new tobacco heating products and electronic nicotine delivery systems (ENDS) is changing the way humans are exposed to nicotine. The purpose of this narrative review is to provide a broad overview of published scientific literature with respect to the effects of nicotine on three key health-related areas: 1) cardiovascular risk, 2) carcinogenesis and 3) reproductive outcomes. These areas are known to be particularly vulnerable to the effects of cigarette smoke, and in addition, nicotine has been hypothesized to play a role in disease pathogenesis. Acute toxicity will also be discussed. The literature to February 2019 suggests that there is no increased cardiovascular risk of nicotine exposure in consumers who have no underlying cardiovascular pathology. There is scientific consensus that nicotine is not a direct or complete carcinogen, however, it remains to be established whether it plays some role in human cancer propagation and metastasis. These cancer progression pathways have been proposed in models in vitro and in transgenic rodent lines in vivo but have not been demonstrated in cases of human cancer. Further studies are needed to determine whether nicotine is linked to decreased fertility in humans. The results from animal studies indicate that nicotine has the potential to act across many mechanisms during fetal development. More studies are needed to address questions regarding nicotine exposure in humans, and this may lead to additional guidance concerning new ENDS entering the market.

An update on prevalence and risk of snus and nicotine replacement therapy during pregnancy and breastfeeding

AIM

In parallel with falling smoking rates, use of the oral moist tobacco product snus increases among women in reproductive age. We report an update on prevalence and effects of maternal use of snus and nicotine replacement therapy (NRT) during pregnancy and breastfeeding.

METHODS

A literature search of human studies in Medline, PubMed and EMBASE was conducted from September 2016 to May 2018, with stepwise screening of abstracts and subsequent relevant full-text papers for inclusion in Scandinavian and English languages.

RESULTS

Based on three studies, the prevalence of snus use in pregnancy was up to 3.4% in the first trimester and 2.1% in the third trimester. In 12 studies, we found increased risk of several adverse effects, especially preterm delivery, stillbirth and small for gestational age associated with maternal snus use during pregnancy. Knowledge on effects of NRT during pregnancy was conflicting and inconclusive in 10 studies. We did not identify any studies on prevalence or potential health effects of snus or NRT during breastfeeding.

CONCLUSION

Few studies with updated data on the prevalence and adverse health effects of maternal use of snus and NRT during pregnancy were found. No studies during breastfeeding were identified.

Comparison of nicotine exposure during pregnancy when smoking and abstinent with nicotine replacement therapy: systematic review and meta-analysis

BACKGROUND AND AIMS

Smoking during pregnancy is strongly associated with negative pregnancy and perinatal outcomes. Some guidelines recommend nicotine replacement therapy (NRT) for smoking cessation during pregnancy, but adherence with NRT is generally poor and could be partially explained by nicotine-related safety concerns. We compared pregnant women's cotinine and nicotine exposures from smoking with those when they were abstinent from smoking and using NRT.

DESIGN

Systematic review with meta-analysis and narrative reporting. Twelve studies were included: in most, only one type of NRT was used. Seven were quality-assessed and judge of variable quality.

SETTING

Studies from any setting that reported nicotine or cotinine levels when smoking and later when abstinent and using NRT.

PARTICIPANTS

Pregnant women who smoked and became abstinent but used NRT either in a cessation study or in a study investigating other impacts of NRT.

MEASUREMENTS

We quality-assessed longitudinal cohort studies using a modified version of the Newcastle-Ottawa scale. For meta-analysis, we used mean within-person differences in cotinine or nicotine levels when smoking and at later follow-up when abstinent and using NRT. Where such data were not available, we calculated differences in group mean levels and reported these narratively, indicating where data were not completely longitudinal.

FINDINGS

Of the 12 included studies, four cotinine-measuring studies (n = 83) were combined in a random effects meta-analysis; the pooled estimate for the mean difference (95% confidence intervals) in cotinine levels between when women were smoking and abstinent but using NRT was 75.3 (57.1 to 93.4) ng/ml (I²  = 42.1%, P = 0.11). Of eight narratively-described studies, six reported lower cotinine and/or nicotine levels when abstinent and using NRT; two had mixed findings, with higher levels when abstinent but using NRT reported from at least one assay time-point.

CONCLUSIONS

Pregnant women who use nicotine replacement therapy instead of smoking reduce their nicotine exposure.

Pharmaceutical strategies for smoking cessation during pregnancy

Introduction: Tobacco use is the most preventable cause of death worldwide, with over 7 million deaths per year. Smoking during pregnancy causes harm to the mother, fetus, and can result in problems for the infant from childhood into adulthood. Practitioners should ask all expectant mothers about tobacco use. For expectant mothers who smoke or recently quit, practitioners should advice to quit and provide psychosocial interventions. Rates of smoking during pregnancy differ between geographical locations, with estimates of 10.8% in the UK and 7.2% in the US. Practitioners should provide expectant mothers unable to quit smoking with information about the risks and benefits of pharmacotherapy and use a patient-centered approach to determine the use. Although there is no definitive evidence on birth outcomes, nicotine replacement therapy and bupropion are adequate pharmacotherapies to help those unable to quit. Areas covered: Herein, this author looks at the various pharmaceutical strategies to help patients cease smoking and provides expert perspectives on the subject. Expert opinion: Additional research on pharmacotherapy is warranted, especially with varenicline. Practitioners working with pregnant patients should be familiar with the evidence for pharmacotherapy in smoking cessation during pregnancy. This evidence can be difficult to navigate due to conflicting results and limitations with the trials.