The effect of female tobacco smoking on IVF outcomes

Environmental factors affecting female fertility

INTRODUCTION

Over the recent years, scientific community has increased its interest on solving problems of female fertility pathology. Many factors acting separately or in combination affect significantly the reproductive life of a woman. This review summarizes current evidence regarding the direct and/or indirect action of environmental factors and endocrine disrupting chemicals (EDCs; i.e. heavy metals, plasticizers, parabens, industrial chemicals, pesticides, or medications, by-products, anti-bacterial agents, perfluorochemicals) upon assisted and non-assisted female fertility, extracted from in vivo and in vitro animal and human published data. Transgenerational effects which could have been caused epigenetically by the action of EDCs have been raised.

METHODS

This narrative review englobes and describes data from in vitro and in vivo animal and human studies with regard to the action of environmental factors, which include EDCs, on female fertility following the questions for narrative reviews of the SANRA (a scale for the quality assessment of narrative review articles). The identification of the studies was done: through the PubMed Central and the PubMed of the MEDLINE, the Google Scholar database and the Cochrane Library database until December 2023 combining appropriate keywords ("specific environmental factors" including "EDCs" AND "specific negative fertility outcomes"); by manual scanning of references from selected articles and reviews focusing on these subjects. It includes references to EDCs-induced transgenerational effects.

RESULTS

From the reported evidence emerge negative or positive associations between specific environmental factors or EDCs and infertility outcomes such as infertility indices, disrupted maturation of the oocytes, anovulation, deranged transportation of the embryo and failure of implantation.

CONCLUSION

The revealed adverse outcomes related to female fertility could be attributed to exposure to specific environmental factors such as temperature, climate, radiation, air pollutants, nutrition, toxic substances and EDCs. The recognition of fertility hazards related to the environment will permit the limitation of exposure to them, will improve female fertility and protect the health potential of future generations.

The endometrial transcriptome of infertile women with and without implantation failure

INTRODUCTION

Implantation failure after transferring morphologically "good-quality" embryos in in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) may be explained by impaired endometrial receptivity. Analyzing the endometrial transcriptome analysis may reveal the underlying processes and could help in guiding prognosis and using targeted interventions for infertility. This exploratory study investigated whether the endometrial transcriptome profile was associated with short-term or long-term implantation outcomes (ie success or failure).

MATERIAL AND METHODS

Mid-luteal phase endometrial biopsies of 107 infertile women with one full failed IVF/ICSI cycle, obtained within an endometrial scratching trial, were subjected to RNA-sequencing and differentially expressed genes analysis with covariate adjustment (age, body mass index, luteinizing hormone [LH]-day). Endometrial transcriptomes were compared between implantation failure and success groups in the short term (after the second fresh IVF/ICSI cycle) and long term (including all fresh and frozen cycles within 12 months). The short-term analysis included 85/107 women (33 ongoing pregnancy vs 52 no pregnancy), excluding 22/107 women. The long-term analysis included 46/107 women (23 'fertile' group, ie infertile women with a live birth after ≤3 embryos transferred vs 23 recurrent implantation failure group, ie no live birth after ≥3 good quality embryos transferred), excluding 61/107 women not fitting these categories. As both analyses drew from the same pool of 107 samples, there was some sample overlap. Additionally, cell type enrichment scores and endometrial receptivity were analyzed, and an endometrial development pseudo-timeline was constructed to estimate transcriptomic deviations from the optimum receptivity day (LH + 7), denoted as ΔWOI (window of implantation).

RESULTS

There were no significantly differentially expressed genes between implantation failure and success groups in either the short-term or long-term analyses. Principal component analysis initially showed two clusters in the long-term analysis, unrelated to clinical phenotype and no longer distinct following covariate adjustment. Cell type enrichment scores did not differ significantly between groups in both analyses. However, endometrial receptivity analysis demonstrated a potentially significant displacement of the WOI in the non-pregnant group compared with the ongoing pregnant group in the short-term analysis.

CONCLUSIONS

No distinct endometrial transcriptome profile was associated with either implantation failure or success in infertile women. However, there may be differences in the extent to which the WOI is displaced.

Factors influencing natural fecundity in fertile couples: a survey of puerperae and their partners

RESEARCH QUESTION

What is the fecundity rate among fertile couples, and which factors influence it?

DESIGN

Retrospective study of all puerperae attending Cruces University Hospital Human Reproduction Unit over 9 months. An anonymous questionnaire was circulated to all patients, and 2510 valid completed questionnaires were collected. The main inclusion criterion was natural conception resulting in delivery. Pregnancies resulting from ART and contraceptive method failure were excluded. Investigated parameters were time to pregnancy, age and smoking (in women and men), previous pregnancies and intercourse frequency. A mathematical formula was developed to predict the per-month fecundity rate (PMFR).

RESULTS

The cumulative fecundity rate was 29.08%, 54.26%, 68.61%, 89.88%, 96.95% and 98.63% (at 1, 3, 6, 12, 24 and 36 months); between 12 and 36 months, the average PMFR ranged from 8.53-7.48%. Only 1.68% of pregnancies occurred between 24 and 36 months, and only 1.37% thereafter. The best fecundity markers were obtained in the group who had sexual intercourse seven to eight times a week. Women and men younger than 25 years had lower fecundity markers than those aged between 25 and 40 years.

CONCLUSIONS

Fertile couples have a non-negligible per-month fecundity rate between 12 and 36 months, which should be considered when planning fertility studies. The lower fecundity rate observed in women and men aged younger than 25 years deserves more study. Coital frequencies of more than two or three times a week did not affect the fecundity rate and was better with frequencies of seven to eight times a week.

Effect of Male Cigarette Smoking on In Vitro Fertilization (IVF) Outcomes and Embryo Morphokinetic Parameters

This retrospective cohort study examines the association between male smoking status and embryo development in vitro. The study included non-smoking women aged under 40 years who underwent in vitro fertilization (IVF) at Yanaihara Women's Clinic from May 2019 to May 2022, and they were divided into two groups according to the husband's smoking status. The effect of male smoking status on IVF outcomes was compared retrospectively based on embryonic development using a time-lapse incubator. A total of 184 patients were included; 272 oocytes of 45 female non-smokers were cultured with the sperm of male smokers, and 816 oocytes of 139 female non-smokers were cultured with the sperm of male non-smokers. No significant differences were observed between male smokers and non-smokers groups with regard to fertilization and the top-quality embryo on day 3 and day 5 (p > 0.05). The male smoker group's embryos reached the early cleavage-stage parameters (time of pronuclei appearance to the five-cell stage) significantly earlier than the male non-smoker group's embryos (p < 0.05). However, no significant differences were observed between the two groups in other parameters of top-quality blastocysts (p > 0.05). It was concluded that male smoking has some differences on the timing of early embryonic events on time-lapse examination.

Associations between smoking status and infertility: a cross-sectional analysis among USA women aged 18-45 years

Background

Although many studies have proven the harmful effects of smoking on human health, the associations between smoking status and infertility are limited in large epidemiologic studies. We aimed to investigate the associations between smoking status and infertility among child-bearing women in the United States of America (USA).

Methods

A total of 3,665 female participants (aged 18-45) from the National Health and Nutrition Examination Survey (NHANES) (2013-2018) were included in this analysis. All data were survey-weighted, and corresponding logistic regression models were performed to investigate the associations between smoking status and infertility.

Results

In a fully adjusted model, the risk of infertility was found to be increased by 41.8% among current smokers compared to never smokers (95% CI: 1.044-1.926, P=0.025). In the subgroup analysis, the odds ratios (95% CI) of the risk of infertility for current smokers were 2.352 (1.018-5.435) in the unadjusted model for Mexican American, 3.675 (1.531-8.820) in the unadjusted model but 2.162 (0.946-4.942) in fully adjusted model for people aged 25-31, 2.201 (1.097-4.418) in the unadjusted model but 0.837 (0.435-1.612) in fully adjusted model for people aged 32-38.

Conclusion

Current smokers was associated with a higher risk of infertility. The underlying mechanism of these correlations still needs more research. Our findings indicated that quitting smoking may serve as a simple index to reduce the risk of infertility.

Benzo[a]pyrene-Environmental Occurrence, Human Exposure, and Mechanisms of Toxicity

Benzo[a]pyrene (B[a]P) is the main representative of polycyclic aromatic hydrocarbons (PAHs), and has been repeatedly found in the air, surface water, soil, and sediments. It is present in cigarette smoke as well as in food products, especially when smoked and grilled. Human exposure to B[a]P is therefore common. Research shows growing evidence concerning toxic effects induced by this substance. This xenobiotic is metabolized by cytochrome P450 (CYP P450) to carcinogenic metabolite: 7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE), which creates DNA adducts, causing mutations and malignant transformations. Moreover, B[a]P is epigenotoxic, neurotoxic, and teratogenic, and exhibits pro-oxidative potential and causes impairment of animals' fertility. CYP P450 is strongly involved in B[a]P metabolism, and it is simultaneously expressed as a result of the association of B[a]P with aromatic hydrocarbon receptor (AhR), playing an essential role in the cancerogenic potential of various xenobiotics. In turn, polymorphism of CYP P450 genes determines the sensitivity of the organism to B[a]P. It was also observed that B[a]P facilitates the multiplication of viruses, which may be an additional problem with the widespread COVID-19 pandemic. Based on publications mainly from 2017 to 2022, this paper presents the occurrence of B[a]P in various environmental compartments and human surroundings, shows the exposure of humans to this substance, and describes the mechanisms of its toxicity.

Does cigarette smoking really have a clinical effect on folliculogenesis and oocyte maturation?

Infertility is the most common issue in the field of reproductive medicine. Many factors affect fertility status, including life-style choices such as cigarette smoking or alcohol use. The aim of this study was to investigate the effects of cigarette smoking on oocyte quality as well the quantity in young fertile women. In total, 56 young fertile women who were undergoing oocyte donation programmes were included in this study. The effects of cigarette smoking on antral follicle count, number of follicles and oocytes retrieved and morphology were assessed by an expert embryologist. The results of this study showed that cigarette smoking did not have a significant effect on the follicle count or the number of oocytes retrieved from young and fertile women. However, a significant difference was observed in the morphological assessment. In conclusion, although cigarette smoking does not seem to affect oocyte development, it had an effect on cytoplasmic anomalies and therefore may lower pregnancy chance. Therefore, it is crucial to give proper counselling to patients who are trying to become pregnant both naturally and by in vitro fertilization.

Melatonin attenuates cadmium-induced ovulatory dysfunction by suppressing endoplasmic reticulum stress and cell apoptosis

BACKGROUND

Increasing evidence demonstrate that cadmium (Cd) has adverse effects on the mammalian reproductive system. However, the mechanisms underlying the effects of Cd on ovarian function and the strategies to reverse these effects have not been fully elucidated.

METHODS

In this study, 60 CD-1 mice were divided into four groups (control, melatonin, Cd, Cd with melatonin). During the treatment for 14 days, body weight was measured every 2 days. After the treatment, ovaries were isolated and weighted to observe the morphological and biological characteristics. Statistical analyses were performed using one-way ANOVA followed by Fisher's-multiple range test or chi-squared test, A P value < 0.05 indicated statistical significance.

RESULTS

We observed that Cd exposure induced ovulatory dysfunction, demonstrated by the reduced number of ovulated oocytes numbers in the Cd group. However, this endoplasmic reticulum (ER) pathway was activated in the Cd-exposed ovaries and the expression of GRP78, ATF4, CHOP, and p-JNK was upregulated, which was reversed by treatment with melatonin. Furthermore, we found that melatonin inhibited Cd-induced activation of cleaved caspase-3, restored the ratio of Bax/Bcl-2, and ultimately decreased the apoptosis of granular cells as detected by TUNEL staining.

CONCLUSION

Collectively, our findings reveal that melatonin attenuated Cd-induced ovulation dysfunction and cell apoptosis by inhibiting the activation of the ER pathway. Thus, melatonin can be a potential agent to protect mammalian ovaries against Cd toxicity.

A systematic review and meta-analysis of lifestyle and body mass index predictors of successful assisted reproductive technologies

OBJECTIVE

Lifestyle (smoking, drinking alcohol) and body mass index (BMI) predictors of successful outcomes in assisted reproductive technology (ART) treatments were examined in this meta-analysis.

METHOD

A bibliographic search was undertaken using six databases. The review was informed by PRISMA/MOOSE guidelines. Meta-analytic data were analysed using random effects models.

RESULTS

We included 77 studies examining effects of BMI, smoking and drinking alcohol. Patients with a BMI< =24.9 were significantly more likely to achieve LB/pregnancy than with BMI> =25 OR = 1.219 (95% CI:1.128-1.319, z = 4.971, p < .001; I² = 53.779%, p = .001). Non-smokers were significantly more likely to achieve a LB or pregnancy than smokers OR = 1.457 (95% CI:1.228-1.727, z = 4.324, p < .001; I² = 51.883; p = .001). Meta-regression revealed the number of embryos transferred significantly moderated the effects of smoking on ART outcomes, and there was a trend indicating primary infertility and high BMI were also significant moderators. The evidence for drinking alcohol was inconclusive due to the small number of studies.

CONCLUSIONS

This meta-analysis confirms that ART treatment success can be predicted with lifestyle factors. Further, non-smokers' relative odds of pregnancy/live birth increase as more embryos were transferred but there was a trend that the odds of pregnancy/live birth decrease with primary infertility and high BMI.

Cigarette smoking impairs clinical outcomes of assisted reproductive technologies: A meta-analysis of the literature

There is convincing evidence that cigarette smoking can impair female reproductive potential. This meta-analysis updates the knowledge regarding the effects of cigarette smoking on clinical outcomes of assisted reproductive technologies (ART). Twenty-six studies were included in this meta-analysis. Results were expressed as odds ratios (OR) with 95% confidence intervals (CI) and statistical heterogeneity between the studies was evaluated with Higgins (I²), Breslow (τ²), Birge's ratio (H²) indices and Chi-square test (χ²). A P-value < 0.05 was considered statistically significant. The analysis showed a significant decrease in live birth rate per cycle for smoking patients (OR 0.59, 95% CI 0.44-0.79; P = 0.0005), a significant lower clinical pregnancy rate per cycle for smoking women (OR 0.53, 95% CI 0.41-0.68; P < 0.0001), and a significant increase in terms of spontaneous miscarriage rate (OR 2.22, 95% CI 1.10-4.48; P = 0.025) for smokers. These findings demonstrate clear negative effects of cigarette smoking on the outcome of ART programs.

Cigarette smoking and hormones

PURPOSE OF REVIEW

The purpose is to provide a summary of the effects of cigarette smoking on steroid hormone metabolism and how it affects female fertility.

RECENT FINDINGS

Components of tobacco smoke such as polycyclic aromatic hydrocarbons lead to transcriptional upregulation of a number of genes, including members of the cytochrome P450 (CYP) family, in particular CYP1B1 and CYP1A1. In humans, CYP1A1 and CYP1A2 are the primary enzymes catalyzing the 2-hydroxylation of estradiol. This pathway shunts available estrogen away from the more estrogenically potent 16α-hydroxylation to the production of catechol estrogens, mainly 2 and 4 hydroxyestradiol.

SUMMARY

Smoking has multiple effects on hormone secretion and metabolism. These effects are mainly mediated by the pharmacological action of tobacco alkaloids (nicotine and its metabolite cotinine). A strong body of evidence indicates that the negative effects of cigarette smoking on fertility compromises nearly every system involved in the reproductive process.

Cigarette smoke impaired maturation of ovarian follicles and normal growth of uterus inner wall of female wild-type and hypertensive rats

Cigarette smoke (CS) is well known to be very harmful to human body functions such as fertility, reproduction, and development. CS is considered to more affect patients with hypertension (HT). To estimate the effect of CS associated with female rat's fertility, we examined the histopathological characteristics of the uterus and ovary which were obtained from the female rats exposed to smoke of the standard cigarette (3R4F) for 4 weeks (10h a week) according to the OECD guidelines. The female wild-type Wistar Kyoto (WK) rats (WTR) and spontaneously hypertensive WK rats (SHR) were used to compare the effect of CS on healthy and hypertensive rats. After CS exposure, we manufactured tissue slides from uterine and ovarian samples and evaluated the maturation of follicles of ovary and cell proliferation in the uterus by H&E staining and immunohistochemistry (IHC). In IHC analysis on ovarian tissues, the expression of proliferating cell nuclear antigen (PCNA) and the number of follicles were decreased by CS exposure. On the contrary, PCNA expression and cell proliferation in the uterine inner layers were increased by CS exposure. The protein expression of C/EBP homologous protein (CHOP), an endoplasmic reticulum (ER)-stress marker, and BAX, a pro-apoptotic protein, was decreased by CS exposure. This phenomenon was more exacerbated in SHR rats than in WTR rats. Taken together, acute exposure to CS induced the decreased maturation of ovarian follicles and abnormal over-growth of uterine inner wall, leading to a harmful effect on female rat's normal function. In addition, this harmful effect of CS may be displayed more seriously in rats with HT.

Ovotoxicity of cigarette smoke: A systematic review of the literature

This study reviews the scientific literature on the noxious effects of cigarette smoke on the ovarian follicle, and the cumulative data on the impact of smoking on in vitro fertilization (IVF) cycle outcome. There is a close association between tobacco smoke and accelerated follicle loss, abnormal follicle growth and impairment of oocyte morphology and maturation. There is an increasing amount of evidence indicating that smoke can directly derange folliculogenesis. Increased cellular apoptosis or autophagy, DNA damage and abnormal crosstalk between oocyte and granulosa cells have been implicated in the demise of ovarian follicles. It becomes increasingly clear that maternal smoking can exert multigenerational effects on the ovarian function of the progeny. Growing evidence suggests that cigarette smoke is associated with decreased results after IVF. Further research is needed to better define the molecular mechanisms behind smoking-induced ovarian disruption.

Cigarette smoke is associated with altered expression of antioxidant enzymes in granulosa cells from women undergoing in vitro fertilization

This study was undertaken to evaluate whether cigarette smoke is associated with changes in the expression of antioxidant enzymes in granulosa cells of women undergoing IVF treatments. For this aim, the expression of three antioxidant enzymes (SOD1, SOD2 and catalase) in non-smokers (n = 20) and smokers (n = 20) was analyzed. There was a statistically significant overexpression of SOD2 and catalase mRNA levels in smokers in comparison with non-smokers. Cigarette smoking was associated with a lower fertilization rate, implantation rate and pregnancy rate in comparison with non-smokers. There was no effect on retrieved oocytes number, metaphase II oocytes number, quality of embryos transferred and live birth rate. These findings suggest that cigarette smoke initiates oxidative stress in granulosa cells.

Cigarette Smoking Affects Uterine Receptivity Markers

OBJECTIVE

Smoking negatively affects fertility and the rate of other endometrial diseases. To determine the effect of smoking on endometrial physiology, we evaluated 2 endometrial regulatory cytokines and receptivity markers, C-X-C motif chemokine ligand 12 (CXCL12) and fibroblast growth factor 2 (FGF2), both in vitro and in vivo.

STUDY DESIGN

The human endometrial stromal cell line (HESC) and primary human endometrial stromal cells were treated with cigarette smoking extract (CSE) or with vehicle control. Twenty female mice were randomly assigned to either cigarette smoke (CS) exposure for 8 weeks or to a nonsmoke (NS) group that received room air. Immunohistochemical analysis of CXCL12 and FGF2 expression was performed in mouse uterine tissue. Human endometrial samples were obtained from both nonsmokers and smokers. Real-time reverse transcription-polymerase chain reaction was performed for all cell cultures and human samples.

RESULTS

Compared to controls, CXCL12 and FGF2 mRNA expression were significantly decreased in CSE-exposed HESC and primary cells. In mice, immunohistochemical analysis showed that both CXCL12 and FGF2 protein expression was lower in the CS group compared to controls. Similarly, both CXCL12 and FGF2 expression were decreased in women who smoke compared to nonsmokers.

CONCLUSION

Decreased endometrial CXCL12 and FGF2 expression contribute to the impaired endometrial receptivity in women who smoke. Smoking is also associated with decreased rates of endometrial cancer and endometriosis; increased CXCL12 and FGF2 are implicated in both conditions. The changes in the expression of cytokines described here may explain the impact of smoking on all of these diseases. Tobacco has direct effects on normal endometrium that impacts endometrial health and disease.

Discrete survival model analysis of a couple's smoking pattern and outcomes of assisted reproduction

Background

Cigarette smoking has been associated with worse infertility treatment outcomes, yet some studies have found null or inconsistent results.

Methods

We followed 225 couples who underwent 354 fresh non-donor assisted reproductive technology (ART) cycles between 2006 and 2014. Smoking history was self-reported at study entry. We evaluated the associations between smoking patterns and ART success using multivariable discrete time Cox proportional hazards models with six time periods: cycle initiation to egg retrieval, retrieval to fertilization, fertilization to embryo transfer (ET), ET to implantation, implantation to clinical pregnancy, and clinical pregnancy to live birth to estimate hazard ratios (HR) and 95% CIs. Time-dependent interactions between smoking intensity and ART time period were used to identify vulnerable periods.

Results

Overall, 26% of women and 32% of men reported ever smoking. The HR of failing in the ART cycle without attaining live birth for male and female ever smokers was elevated, but non-significant, compared to never smokers regardless of intensity (HR = 1.02 and 1.30, respectively). Female ever smokers were more likely to fail prior to oocyte retrieval (HR: 3.37; 95% CI: 1.00, 12.73). Every one cigarette/day increase in smoking intensity for females was associated with a HR of 1.02 of failing ART (95% CI: 0.97, 1.08), regardless of duration or current smoking status. Women with higher smoking intensities were most likely to fail a cycle prior to oocyte retrieval (HR: 1.07; 95% CI: 1.00, 1.16). Among past smokers, every additional year since a man had quit smoking reduced the risk of failing ART by 4% (HR: 0.96; 95% CI: 0.91, 1.00) particularly between clinical pregnancy and live birth (HR: 0.86; 95% CI: 0.76, 0.96).

Conclusions

Female smoking intensity, regardless of current smoking status, is positively associated with the risk of failing ART cycles between initiation and oocyte retrieval. In men who ever smoked, smoking cessation may reduce the probability of failing ART, particularly between clinical pregnancy and live birth.

Trial registration

NCT00011713. Registered: 27 February 2001.

Electronic supplementary material

The online version of this article (doi:10.1186/s40738-017-0032-2) contains supplementary material, which is available to authorized users.

Crosstalk between oral and general health status in e-smokers

Electronic cigarette (e-cigarette) simulates the act of tobacco smoking by vaporizing a mixture of propylene glycol, nicotine, and flavoring agents. e-cigarette has been proposed as a product able to aid to stop smoking. The aim of the study is to verify the clinical variations of periodontal health induced by e-cigarettes use and, moreover, to investigate about the awareness of the e-smokers about their health variations and about their hypothetical need to turn back to smoke combustible cigarettes.This clinical observational pilot study involved 110 out of 350 smokers, who switched to e-cigarette. Patients were subjected to oral examinations. A questionnaire to self-assess the variations of some parameters of general health, and to self-assess the need to smoke combustible cigarettes, was distributed to such subjects involved in the study.At the end of the study, we registered a progressive improvement in the periodontal indexes, as well as in the general health perception. Finally, many patients reported an interesting reduction in the need to smoke.In the light of this pilot study, the e-cigarette can be considered as a valuable alternative to tobacco cigarettes, but with a positive impact on periodontal and general health status.

The prevalence of positive urinary cotinine tests in Korean infertile couples and the effect of smoking on assisted conception outcomes

OBJECTIVE

Smoking has been reported to harm nearly every organ of the body, but conflicting results have been reported regarding the effects of smoking on assisted conception. In this prospective cohort study, we aimed to investigate the prevalence of positive urinary cotinine tests in infertile couples and whether cotinine positivity was associated with infertility treatment outcomes.

METHODS

A qualitative urinary cotinine test was administered to 127 couples who underwent in vitro fertilization (IVF, n=92) or intrauterine insemination (IUI, n=35).

RESULTS

The overall prevalence of positive urinary cotinine test was 43.3% (55/127) in the male partners and 10.2% (13/127) in the female partners with similar prevalence rates in both genders in the IUI and IVF groups. Semen characteristics, serum markers of ovarian reserve, and number of retrieved oocytes were comparable among cotinine-positive and cotinine-negative men or women (with the exception of sperm count, which was higher among cotinine-positive men). The results of urinary cotinine tests in infertile couples were not associated with IVF and IUI outcomes.

CONCLUSION

The presence of cotinine in the system, as indicated by a positive urinary cotinine test, was not associated with poorer outcomes of infertility treatment.

Through the smoke: use of in vivo and in vitro cigarette smoking models to elucidate its effect on female fertility

A finite number of oocytes are established within the mammalian ovary prior to birth to form a precious ovarian reserve. Damage to this limited pool of gametes by environmental factors such as cigarette smoke and its constituents therefore represents a significant risk to a woman's reproductive capacity. Although evidence from human studies to date implicates a detrimental effect of cigarette smoking on female fertility, these retrospective studies are limited and present conflicting results. In an effort to more clearly understand the effect of cigarette smoke, and its chemical constituents, on female fertility, a variety of in vivo and in vitro animal models have been developed. This article represents a systematic review of the literature regarding four of experimental model types: 1) direct exposure of ovarian cells and follicles to smoking constituents' in vitro, 2) direct exposure of whole ovarian tissue with smoking constituents in vitro, 3) whole body exposure of animals to smoking constituents and 4) whole body exposure of animals to cigarette smoke. We summarise key findings and highlight the strengths and weaknesses of each model system, and link these to the molecular mechanisms identified in smoke-induced fertility changes.

The effects of cigarette smoke extract on ovulation, oocyte morphology and ovarian gene expression in mice

Cigarette smoking can harm fertility, but the existing research has targeted primarily on ovarian follicles, embryos or sex hormone. In this study, we tested cigarette smoke extract on ovulation, oocyte morphology and ovarian gene expression associated with inhibition of oxidative stress using C57BL/6 mice. Mice in the experimental group were administered a cigarette smoke extract (CSE) solution (2 mg/ml) orally daily, while the blank control group was given dimethylsulfoxide (DMSO). A positive control group (menadione) was used that received an intraperitoneal injection of 15 mg/kg menadione in oil solution daily. We found that the CSE group manifested a reduced diameter of zona pellucida-free oocyte (ZP-free OD) and a morphologically misshapen first polar body (PB). Our results suggest that CSE exposure is associated with a shrink size and poor quality of oocytes. Quitting smoking is a wise choice to ensure good fertility.

Scrambled and fried: cigarette smoke exposure causes antral follicle destruction and oocyte dysfunction through oxidative stress

Cigarette smoke is a reproductive hazard associated with pre-mature reproductive senescence and reduced clinical pregnancy rates in female smokers. Despite an increased awareness of the adverse effects of cigarette smoke exposure on systemic health, many women remain unaware of the adverse effects of cigarette smoke on female fertility. This issue is compounded by our limited understanding of the molecular mechanisms behind cigarette smoke induced infertility. In this study we used a direct nasal exposure mouse model of cigarette smoke-induced chronic obstructive pulmonary disease to characterise mechanisms of cigarette-smoke induced ovotoxicity. Cigarette smoke exposure caused increased levels of primordial follicle depletion, antral follicle oocyte apoptosis and oxidative stress in exposed ovaries, resulting in fewer follicles available for ovulation. Evidence of oxidative stress also persisted in ovulated oocytes which escaped destruction, with increased levels of mitochondrial ROS and lipid peroxidation resulting in reduced fertilisation potential. Microarray analysis of ovarian tissue correlated these insults with a complex mechanism of ovotoxicity involving genes associated with detoxification, inflammation, follicular activation, immune cell mediated apoptosis and membrane organisation. In particular, the phase I detoxifying enzyme cyp2e1 was found to be significantly up-regulated in developing oocytes; an enzyme known to cause molecular bioactivation resulting in oxidative stress. Our results provide a preliminary model of cigarette smoke induced sub-fertility through cyp2e1 bioactivation and oxidative stress, resulting in developing follicle depletion and oocyte dysfunction.

[Effects of cigarette smoking on female reproduction: from oocyte to embryo (Part I)]

Cigarette smoking is associated with lower fecundity rate, adverse reproductive outcomes and higher risk of IVF failure. Over the last decades, prevalence of smoking among women of reproductive age has increased. The aim of this work was to focus on the knowledge of the effects of cigarette smoking on all reproductive stages, from oocyte to embryo. For each reproductive functions human clinical and experimental studies were analysed in order to find hypothesis and explanations for effects observed. All reproductive functions are targets of smoke compounds and cigarette smoking impairs ovarian reserve, sexual steroids synthesis, Fallopian tubes functions and embryo development, leading to reduced fecundity. Some of smoke compounds were identified in ovarian tissue, in uterine fluid and in the embryo, suggesting direct toxicity.

Increased zona pellucida thickness and meiotic spindle disruption in oocytes from cigarette smoking mice

BACKGROUND The precise effects of cigarette smoking on female fertility have not yet been clearly defined. We have used a mouse model that mimics human smoking and is able to control for variables that may confound clinical studies to assess the impact of chronic smoking on the quality of mouse oocytes. METHODS Mice received cigarette smoke directly to their lungs for 12 weeks. Lung tissue was analyzed for emphysematous changes and cumulus enclosed oocytes (CEOs) were recovered to study their quality. CEOs were in vitro matured, fixed and stained for chromatin and tubulin. Meiotic spindles, chromatin and the zona pellucida were all examined using confocal microscopy. RESULTS After 12 weeks of cigarette smoking, mice developed alveolar tissue damage that was determined by an increase in destructive index of the lung parenchyma. The numbers of oocytes recovered and the rates of oocyte maturation were not significantly different from non-smoking mice. However, oocytes from smoking mice had a significantly thicker zona pellucida along with shorter and wider meiotic spindles. Furthermore in total, almost a quarter of oocytes from smoking mice were abnormal as assessed by either errors in chromosomal congression or spindle shape. CONCLUSIONS We have used a novel model of inhalational cigarette smoking to show that chronic smoking has a detrimental effect on oocyte quality, and this can be observed even though oocytes are removed from the ovary and cultured in vitro.

Smoking among French infertility specialists: habits, opinions and patients' management

OBJECTIVE

The deleterious effects of tobacco on fertility are now largely demonstrated. Little is known, however, about how infertility doctors communicate on smoking and about their own smoking habits. In this study, we examined smoking habits among French infertility specialists and their attitudes towards infertile couples' exposure to tobacco.

STUDY DESIGN

A postal survey was sent in 2009 to the 803 French certified physicians (gynaecologists, urologists, endocrinologists and embryologists) specializing in infertility. Demographical data, smoking habits and attitude towards patients' smoking were recorded. Statistical analysis and multiple correspondence analysis were performed in order to identify differences among physicians according to age, gender, occupation or smoking status.

RESULTS

Response rate was 42.3%. Half of the respondents were male, 41% were under 45 years, 37% were embryologists and 53.3% were gynaecologists. Thirteen percent reported current smoking. More than 80% always asked their patients about smoking status and cannabis consumption. Most physicians specifically informed infertile couples on tobacco, advised them to quit and proposed smoking cessation therapies. Only 24% refused care unless smoking cessation occurred. Statistical analysis showed some differences among subgroups according to gender, occupation or age. Surprisingly, results were comparable according to smoking status.

CONCLUSION

Most infertility specialists are aware of the deleterious effects of tobacco on fertility and ask their patients to quit. The heterogeneity in infertile patients' management, however, underlines the need for better professional and patients' information on smoking.

Chronic psychosocial stressors are detrimental to ovarian reserve: a study of infertile women

OBJECTIVE

In a cross sectional study of 89 infertile women, we explore a relationship between aspects of psycho-social stress and ovarian reserve parameters.

METHODS

Questionnaires assessed general health and mood (profile of mood state) were administered. Serum (cycle days 1-3) was collected for biomarkers of ovarian reserve (follicle stimulating hormone (FSH), Mullerian Inhibitory Substance, Inhibin B) and stress (Cortisol). Multivariable regression analyses evaluated associations between parameters of interest (dysphoric mood, morning serum cortisol levels reflecting current stress; personal history of abuse, family and/or personal history of substance abuse reflecting chronic stress), with ovarian reserve biomarkers and with the likelihood of being diagnosed with diminished ovarian reserve (DOR).

RESULTS

Women with DOR were almost four times more likely to acknowledge personal history of recreational substance use (0.023) and family history of early menopause (p = 0.018). Adjusted analyses demonstrated advancing age, family history of early menopause, body mass index and chronic psycho-social stressors as independent correlates to serum FSH levels; age, family history of early menopause and chronic stress were predictive of likelihood for DOR. No demonstrable relationship was observed between ovarian reserve and current stress.

CONCLUSIONS

Our findings identify aspects reflecting 'chronic' lifetime psycho-social stressors (i.e., personal history of abuse and of recreational drug use and/or family history of drug use) rather than 'current' stress (as reflected by dysphoric mood score and morning serum cortisol level) as detriments to ovarian reserve (i.e., were predictive of higher FSH levels and of an enhanced likelihood for DOR).

Effects of cigarette smoking on reproduction

BACKGROUND Cigarette smoking is associated with lower fecundity rates, adverse reproductive outcomes and a higher risk of IVF failures. Over the last few decades, prevalence of smoking among women of reproductive age has increased. This review focuses on current knowledge of the potential effects of smoke toxicants on all reproductive stages and the consequences of smoke exposure on reproductive functions. METHODS We conducted a systematic review of the scientific literature on the impact of cigarette smoking and smoke constituents on the different stages of reproductive function, including epidemiological, clinical and experimental studies. We attempted to create hypotheses and find explanations for the deleterious effects of cigarette smoke observed in experimental studies. RESULTS Cigarette smoke contains several thousand components (e.g. nicotine, polycyclic aromatic hydrocarbons and cadmium) with diverse effects. Each stage of reproductive function, folliculogenesis, steroidogenesis, embryo transport, endometrial receptivity, endometrial angiogenesis, uterine blood flow and uterine myometrium is a target for cigarette smoke components. The effects of cigarette smoke are dose-dependent and are influenced by the presence of other toxic substances and hormonal status. Individual sensitivity, dose, time and type of exposure also play a role in the impact of smoke constituents on human fertility. CONCLUSIONS All stages of reproductive functions are targets of cigarette smoke toxicants. Further studies are necessary to better understand the deleterious effects of cigarette smoke compounds on the reproductive system in order to improve health care, help to reduce cigarette smoking and provide a better knowledge of the molecular mechanisms involved in reproductive toxicology.

Review: Toxicants in reproductive fluid and in vitro fertilization (IVF) outcome

Some of the physical, chemical, dietary, occupational and environmental factors are having adverse effect on human reproduction. Increasing trend in reproductive disorders in recent years at least in part might be associated with these factors. The data available suggests less success rate of in vitro fertilization (IVF) outcome of parents exposed to some of the reproductive toxic chemicals as compared to parents who were not exposed to such chemicals. However, data are very meager and require more studies as some debatable data also exists. But existing positive findings encourage in advising that sub-fertile subjects, who are planning to go for the IVF, should reduce toxic exposure well in advance by adopting positive life style and work environment. Further, clinician ought to be aware of occupational and environmental exposure history of the participating couple.

Effect of female nargile smoking on in vitro fertilization outcome

OBJECTIVE

Smoking is a significant health hazard that has been associated with poor reproductive outcome and reduced fertility in reproductive age women. The aim of this study was to assess the effect of nargile smoking on intra-cytoplasmic sperm injection (ICSI) outcome.

STUDY DESIGN

A prospective analysis of the outcomes of 297 women who underwent ICSI treatment at the ART Unit at the American University of Beirut Medical Center between January 1, and December 31, 2006 was done. The patients were divided into 3 groups based on their smoking status: cigarette smokers (n=42), nargile smokers (n=51) and non-smokers (n=204).

RESULTS

The mean age of nargile smokers was significantly lower than the other groups; however, the 3 groups were similar with respect to the cause of infertility, total dose of follicular stimulating hormone (FSH), number of oocytes and embryos obtained, and number and quality of embryos transferred. There was no significant difference in the clinical pregnancy rate between nargile smokers and non-smokers (51.0% vs 43.6%). However, cigarette smokers had a significantly lower clinical pregnancy rate compared to non-smokers (23.8% vs 43.6%, p=0.0238). On multiple logistic regression analysis, factors that decreased the clinical pregnancy rates were cigarette smoking and maternal age.

CONCLUSION

Although this study did not find a deleterious effect of nargile smoking on ICSI outcome, the results need to be confirmed in prospective studies that would include larger number of women with more objective measures of nargile smoke exposure.

Recent cigarette smoking and assisted reproductive technologies outcome

OBJECTIVE

To assess the association between recent cigarette smoking (CS) in female and male partners and assisted reproduction technology (ART) outcomes.

DESIGN

Cohort prospective study.

SETTING

University ART program in Chile.

PATIENT(S)

One hundred sixty-six couples seeking pregnancy through ART.

INTERVENTION(S)

Follicular fluid (FF) and serum cotinine concentrations were measured in female partners. Self-reported CS data were collected through personal interviews.

MAIN OUTCOME MEASURE(S)

The association between female recent smoking, assessed by FF and serum cotinine concentrations, and ART outcomes, such as number of ova retrieved and implantation rates, and the association between self-reported male recent smoking and live birth rates.

RESULT(S)

A significant age-adjusted association between increased FF cotinine level and decreased number of ova retrieved was found. The male partner's smoking habit significantly decreased the live birth rate from 21.1% to 7.8%. Serum cotinine concentrations paralleled those of FF.

CONCLUSION(S)

The hypothesis of a detrimental effect of recent female smoking over implantation rates is rejected. However, recent male smoking is associated with significantly decreased live birth rates even after adjusting for confounders. Female recent smoking was significantly associated with decreased number of retrieved ova.

Effects of cigarette smoking upon clinical outcomes of assisted reproduction: a meta-analysis

BACKGROUND

The aim of this meta-analysis was to investigate whether any difference exists in success rate of clinical outcomes of assisted reproductive technologies (ART) between women who actively smoke cigarettes at the time of treatment and those who do not.

METHODS

An intensive computerized search was conducted on published literature from eight databases, using search terms related to smoking, assisted reproduction and outcome measures. Eligible studies compared outcomes of ART between cigarette smoking patients and a control group of non-smoking patients and reported on live birth rate per cycle, clinical pregnancy rate per cycle, ectopic pregnancy rate per pregnancy or spontaneous miscarriage rate per pregnancy, and 21 studies were included in the meta-analyses. Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated for the data, and statistical heterogeneity was tested for using chi(2) and I(2) values. A systematic review examined the effect of smoking upon fertilization rates across 17 studies.

RESULTS

Smoking patients demonstrated significantly lower odds of live birth per cycle (OR 0.54, 95% CI 0.30-0.99), significantly lower odds of clinical pregnancy per cycle (OR 0.56, 95% CI 0.43-0.73), significantly higher odds of spontaneous miscarriage (OR 2.65, 95% CI 1.33-5.30) and significantly higher odds of ectopic pregnancy (OR 15.69, 95% CI 2.87-85.76). A systematic literature review revealed that fertilization rates were not significantly different between smoking and non-smoking groups in most studies.

CONCLUSIONS

This meta-analysis provides compelling evidence for a significant negative effect of cigarette smoking upon clinical outcomes of ART and should be presented to infertility patients who smoke cigarettes in order to optimize success rates.

Cigarette smoking and reproductive function

PURPOSE OF REVIEW

To perform a systematic review of the literature on the relationship between cigarette smoking and reproductive function. Whenever possible, this review is focused on the most recently published studies (mainly the past 2 years). Nevertheless, in many instances older literature was too relevant not to be taken into account.

RECENT FINDINGS

Tobacco compounds exert a deleterious effect on the process of ovarian follicle maturation. This effect is expressed by worse in-vitro fertilization parameters in cycles performed on women with smoking habits. Also, uterine receptiveness is significantly altered by the smoking habit. In men, cigarette smoking reduces sperm production, increases oxidative stress, and DNA damage. Spermatozoa from smokers have reduced fertilizing capacity, and embryos display lower implantation rates. Even in-utero exposition to tobacco constituents leads to reduced sperm count in adult life.

SUMMARY

A strong body of evidence indicates that the negative effect of cigarette smoking on fertility comprises fairly every system involved in the reproductive process. Couples in reproductive age should be strongly discouraged to smoke.

Validity of the in vitro fertilisation league tables: influence of patients' characteristics

We tested the hypothesis that restricting comparison of the live birth rate following in vitro fertilisation (IVF) treatment in those couples having their first IVF cycle in whom the female is under 35 years of age and has a normal follicle-stimulating hormone level would improve the validity of comparing IVF clinics' success rates. We analysed all cycles performed over a 2-year period in patients who fulfilled these criteria and divided the study population according to the referring primary care trusts: group A (n = 90) were referred from Lambeth, Southwark and Lewisham and group B (n = 134) were referred from Brent and Harrow. There was no significant difference between the two groups with regard to their IVF cycle characteristics. The two groups differed in their ethnicity, cause of infertility, prevalence of uterine fibroids and smoking and alcohol consumption habits. Group A had a significantly lower live birth rate (OR = 0.45, 95% CI 0.21-0.95, P = 0.02) compared with group B. This study confirms the impact of the non-IVF-related patient characteristics on treatment outcome and the poor validity of comparing IVF clinics' success rates based on the sparse data published by national IVF registries.

Epidemiology of prenatal smoking and perinatal outcomes

During the previous two decades smoking among pregnant women in the developed world declined by about 60-75%. Nevertheless, prenatal smoking remains a common habit and accounts for a significant proportion of fetal morbidity and mortality through both a direct (fetal) and an indirect (placental) effect. The most important smoking-induced placental pathology is placental abruption with reported risk estimates ranging from 1.4 to 4.0. It is almost a consensus that prenatal smoking is a causative factor for placental abruption. Although the evidence is less compelling, smoking mothers are at an increased risk for placenta previa and placenta-previa-accreta combination. There is no association between maternal smoking and the syndrome of idiopathic uterine bleeding. The relationship between maternal smoking and fetal growth is causal, and includes significant reduction in growth of head circumference, abdominal circumference and femur length, with the largest reduction in size observed for femur length. Prenatal smoking is associated with a 20-30% higher likelihood for stillbirth, a 40% elevation in the risk for infant mortality and a 2-fold increase in the incidence of SIDS.

CONCLUSION

Despite a temporal decline in maternal smoking, it still accounts for significant feto-infant morbidity and mortality, and efforts to discourage prenatal smoking need to be intensified.