The impact of several lifestyle factors including; age, weight, smoking, diet, exercise, psychological stress, caffeine consumption, alcohol consumption and exposure to environmental pollutants are included in the review. However, not all studies have found an association between caffeine consumption and spontaneous abortion Mills et al. The studies were assessed for quality and the evidence for each lifestyle factor was summarized and sorted as providing either conclusive or inconclusive evidence of an effect. In contrast, a study Zaadstra et al. A randomized controlled trial of 60 couples attending a Turkish Hospital for their first IVF treatment Terzioglu, found a statistically significant association between providing counselling and support to couples and increased pregnancy rates. The summation of evidence of associations between psychological stress, caffeine, alcohol consumption and reproductive performance is inconclusive.
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It is concluded that lifestyle modification can assist couples to conceive spontaneously or optimize their chances of conception with ART treatment. Lifestyle factors are behaviours and circumstances that are, or were once, modifiable and can be a contributing factor to subfertility.
Fertility is the capacity to produce offspring, whereas fecundity is a woman's biological ability to reproduce based on the monthly probability of conception Wood, Clinical infertility is defined as the inability to become pregnant after 12 months of unprotected intercourse.
The causes of infertility are wide ranging including diagnoses such as, ovulatory disorders, tubal disease, endometriosis, chromosomal abnormalities, sperm factors and unexplained infertility. The impact of lifestyle on reproductive performance may vary depending on individual aetiology and circumstances. Lifestyle factors have had a dramatic impact on general health and the capacity to reproduce. Lifestyle issues such as smoking and obesity can affect general health and well-being.
For example, smoking increases an individual's risk of cardiovascular disease Leone, and adverse consequences associated with obesity include increased risk of cardiovascular disease, diabetes and some cancers Haslam and James, There is an increasing body of evidence that lifestyle factors can impact on reproductive performance.
For example, studies have demonstrated that smoking in women significantly decreases the chance of conception Hughes and Brennan, ; Augood et al.
Post-industrial western society has created the potential for increasing the exposure to specific lifestyle factors and behaviours that can positively or negatively affect reproductive health.
For example, obesity is often associated with lack of exercise and inappropriate diet Cameron et al. The aim of this paper is to review the impact of a specific range of contemporary lifestyle factors on fertility.
The review focuses on the non-communicable aetiology for fertility associated with potentially modifiable lifestyle factors. These factors include female age, smoking, weight, diet, exercise, psychological stress, caffeine consumption, alcohol consumption and exposure to environmental pollutants. This review is divided into two sections.
In the first section, individual lifestyle factors are considered where there is conclusive evidence for effect, followed by a review of factors where the evidence is equivocal. For the purpose of this review, a comprehensive search of the literature was performed using the following search strategy.
The information databases of Medline, PubMed and Cinahl were searched to identify relevant publications written in English between and Publications that focused on reproductive performance and specific lifestyle factors were reviewed. In particular, publications that studied general populations or infertile populations undergoing assisted reproductive technology ART were targeted. Specific reference to infertility, age, smoking, weight, caffeine, alcohol, exercise and diet were sought using key words, including lifestyle, infertility, fertility, subfecundity, fecundity, preconception, pregnancy, smoking, age, weight, obesity, caffeine, alcohol, environment, exercise, diet, nutrition, IVF and ART.
Abstracts were critically appraised and the full article sought and read if the abstract was considered robust and relevant. The studies were assessed for quality and the evidence for each lifestyle factor was summarized and sorted as providing either conclusive or inconclusive evidence of an effect.
Key papers for each subject were referenced in view of space limitations. In the following sections, individual factors that have the potential to impact on reproductive health are reviewed. By the time women reach 35 years of age, their fertility is declining Pal and Santoro, ; Baird et al. At an even earlier age, the number and quality of oocytes decrease but manifest clinically at around 35 years of age Angell, ; Benadiva et al.
In addition, the incidence of genetic abnormalities and spontaneous abortion increase observably with maternal age Nasseri and Grifo, The Hutterite population is an isolated community that live a relatively simple communal lifestyle that excludes the use of contraception. This community provides, therefore, a benchmark of natural fertility when examining fertility in other populations Wood, The Hutterite population have a progressive decline in the rate of pregnancies with increasing female age Larsen and Vaupel, Apparent fecundity and natural fertility in humans.
Based on Bendal and Hua's re-analysis of data on the first birth interval from Taiwan Juan, and data on all birth intervals in the Hutterites Shep, Republished from Wood Age curve of apparent fecundability, with permission. Further evidence comes from a recent observational study asking pregnant women how long it took them to conceive. A study of pregnant women from the UK reported that increasing age for both men and women adversely affected the time taken to conceive Hassan and Killick, A similar pattern was found in a study of seven European centres Dunson et al.
A large sample of women attending these European centres for natural fertility advice and planning was followed. Women in this study aged 19—26 had a significantly higher chance of pregnancy than women aged 35— A negative effect of increasing male age particularly in the late 30s was also found, although the aetiology for this is uncertain.
The studies discussed here are all relatively large and some have taken into account the confounding factors that may impact on the time taken to conceive. All report a consistent and statistically significant decline in fertility associated with increasing female age. The magnitude of this decline is clinically and socially important. Despite the substantial evidence of an age-related decline in female fertility, women are often ignorant of the risks associated with delaying child bearing.
A recent study of university students in Sweden found that half of the female students intended to have children after the age of 35 years and were unaware of the age-related decline in fertility associated with increasing age Lampic et al. The effect of the age of women undergoing ART is similar to the general population with pregnancy rates declining with increasing age Hull et al.
The average age of these women was Women in the age range of 25—29 years undergoing fresh non donor treatment cycles, achieved a live birth rate of These figures concur with the general population trend where peak fecundity occurs at the age of 22 years, begins to decline in the mid- to late- 20s and has plummeted by the age of 40 years Wood, The trend in Australia and New Zealand is typical of global experience.
A Belgium study of couples undergoing IVF because of obstructive and non-obstructive azoospermia also found that increasing maternal age progressively affected live delivery rate per cycle. The practice of reporting success by pregnancy rate is contentious. Commonly, success is claimed on the achievement of pregnancy. This has been the recommendation by at least one expert panel Baird et al. The poor live birth rate in older women is, in great part, due to spontaneous abortion.
A study of pregnancies from women undergoing ovulation induction found a 2. Another study of consecutive ICSI cycles undertaken in a New York hospital found a significant decline in clinical pregnancy rate, implantation rate and delivery rate per embryo transfer associated with increasing female age Spandorfer et al. Delivery per embryo replaced was However, they were not able to identify an effect of paternal age on the outcomes.
Cigarette smoking has been association with adverse effects on fertility, although this is not widely recognized Roth and Taylor, There is strong evidence of the adverse effects of smoking on fertility operating through a range of pathways in both the general and infertile population. In males, smoking negatively affects sperm production, motility and morphology and is associated with an increased risk of DNA damage Zenzes et al.
In the female, the constituents of cigarette smoke may affect the follicular microenvironment and alter hormone levels in the luteal phase. Cotinine and cadmium have been detected in the follicular fluid of female smokers and whose partner smokes, thus having access to the developing follicle Younglai et al.
Menopause has been reported to occur 1—4 years earlier for women who smoke compared to non-smokers Baron et al. A recent study demonstrated an increased thickness of the zona pellucida in smokers, which may make it more difficult for sperm penetration Shiloh et al.
A meta-analysis of 12 studies found the overall OR for risk of infertility in the general population was 1. An OR of 1. A study of couples from 10 European countries also found a strong association between female smoking and subfecundity Bolumar et al. A systematic review reported that 12 out of 13 studies demonstrated a negative effect of female smoking on conception Hughes and Brennan, Republished from Augood et al.
A meta-analysis of nine studies found an OR of 0. Another meta-analysis reported that almost twice as many IVF cycles were needed to achieve pregnancy for smokers compared with non-smokers Feichtinger et al. These effects were observed against a cycle-specific pregnancy rate of Similarly, a study of women undergoing IVF found that smokers did not respond as well to stimulation as non-smokers, fertilization was lower and none of the regular smokers became pregnant Crha et al.
The risk increased with each year of smoking. A recent review of lifestyle habits and IVF concluded that there was compelling evidence of the negative effect of smoking on IVF outcome Klonoff-Cohen, There is also emerging evidence of adverse effects on reproduction associated with passive smoking. A recent study of women undergoing IVF found that fertilization rates were similar for smokers, passive smokers and non-smokers, whereas pregnancy rates were significantly decreased for smokers Smoking has been shown to adversely affect the chance of pregnancy from ART, with results of studies suggesting that smokers require nearly twice as many IVF cycles to conceive as non-smokers Feichtinger et al.
Obesity is associated with a range of adverse health consequences. Widely recognized are the increased risks of cardiovascular disease, diabetes and some cancers. Obesity and low body weight can impact on reproductive function by causing hormone imbalances and ovulatory dysfunction. The effect of adolescent BMI at age 18 as a predictor of ovulatory infertility was examined. Compared to women with a BMI of 20— The risk of infertility with increasing BMI was apparent for women with and without polycystic ovarian disease.
Relative risk of infertility by BMI at age Republished from Rich-Edwards et al. Supporting these findings is a study that investigated lifestyle factors in pregnant women. Another large study of women from five European countries Bolumar et al. Obesity has been shown to decrease the probability of pregnancy for women undergoing ART. A large Australian study of women who underwent ART found that pregnancy rates were halved for very obese women in comparison with women with a normal BMI Wang et al.
Further evidence was found in a study of women undergoing IVF. After adjusting for age and the number and quality of embryos, the chance of pregnancy was halved for overweight women OR 0. The distribution of body fat also impacts on reproductive performance but the mechanism for this effect is unclear Norman et al.
A prospective study of apparently normal women undergoing donor insemination Zaadstra et al. These results are particularly significant as the women required ART treatment because of male factor infertility and therefore reflected a relatively normal population with few of them requiring stimulation. This contrasts with women with a normal BMI of The lower rate in the obese group was mainly due to an increased risk of early pregnancy loss. High BMI in women has also been associated with other adverse pregnancy outcomes such as gestational diabetes and hypertension Michlin et al.
The evidence for the effects of weight on reproduction from observational studies has given rise to a number of significant intervention studies.
Lifestyle modification programmes that include exercise have been shown to assist women to lose weight, improve their fitness, increase psychological well-being and improve reproductive functioning Clark et al. The women in this study attended a weekly programme for 6 months that included an exercise component and education relating to diet and psychological issues associated with being overweight. Although the number of women taking part in the study was relatively low, the positive effects of participating in the programme were outstanding.
On average, the women lost Of the 67 women who completed the study, Eating a healthy diet consisting of appropriate composition and caloric intake is fundamental to maintaining a state of optimum physical and psychological health. It is also important in preventing diseases such as obesity, cardiovascular disease, diabetes, osteoporosis and some cancers. Diet mediates body weight and composition and should be considered fundamental to reproduction. However, although a link has been demonstrated between maternal nutritional status and adverse pregnancy outcomes Fall et al.
Early pregnancy is a vulnerable period for embryo and fetal development and the environment at the time of conception can impact on the developing embryo and subsequent long-term health of the child Chapin et al.
Studies directly relating dietary components to the chance of conceiving are sparse in humans. However, there is strong evidence that a well-balanced healthy diet is beneficial for general well-being and optimum body functioning Sanders, and it has been suggested that diet before pregnancy may influence fetal well-being Moore and Davies, Therefore, reproductive performance should be positively influenced by the consumption of a healthy varied diet.
Regular exercise affects an individual's general health and well-being and probably provides some protection from obesity, cardiovascular disease, hypertension, diabetes, osteoporosis and psychological stress. Research in relation to physical fitness and reproduction is primarily focused on athletes rather than women who have a moderate level of fitness. However, there was no association with moderate exercise.
This is in contrast to the Clark et al. The women in this study underwent a 6-month lifestyle modification programme that included a weekly group fitness component and at least two further exercise sessions per week. In addition to losing weight, each participant's fitness level improved. Exercise increases insulin sensitivity, which improves ovarian function and the chance of conception Norman and Clark, Exercise during pregnancy has also been reported to increase maternal well-being Morris and Johnson, The overall physical, emotional and increased general well-being benefits of being physically fit are well documented Berlin and Colditz, ; Sandvik et al.
However, there is a need for further research regarding the effects that moderate and low-level exercise may have on reproductive performance. It is reasonable to assume that the general health benefits associated with moderate levels of exercise and the consumption of a well-balanced diet would also apply to fertility.
These lifestyle practices should therefore be recommended to couples attempting pregnancy. Further research is needed to clarify the effect that exercise may play on reproductive performance.
The above evidence associated with age, smoking and weight shows that there is strong substantiation of an adverse association between these lifestyle factors and the risk of impaired fertility. Other lifestyle factors such as psychological stress, caffeine and alcohol consumption and environmental pollutants may impact on reproductive health and adversely affect fertility. However, so far, the evidence is limited and not consistent across studies. Psychological stress may reduce female reproductive performance in various ways.
The autonomic nervous system, the endocrine and immune systems have all been implicated Hjollund et al. Given that infertility and ART treatment are associated with stress Hammarberg et al. A randomized controlled trial compared a cognitive behavioural group, a support group and a control in women attempting to conceive for 1—2 years both naturally and from ART treatment Domar et al. Women were randomized into one of three groups: The first intervention group was a cognitive behavioural group where participants were taught relaxation and cognitive restructuring techniques.
They were also given information about nutrition and exercise. In light of the evidence above, providing this type of information may be a potential confounder of a direct effect on psychological factors. The second intervention group was a support group. Participants were encouraged to discuss issues such as infertility treatment and their emotional feelings, followed by a more structured information session on a topic such as the impact of infertility on self-esteem.
The women also met with a psychologist twice during the year of follow-up for testing of stress levels. An observational study Hjollund et al. Couples were followed for six menstrual cycles. Decreased conception was associated with women who reported being most stressed The effects seen in the general population carry over to women undergoing ART treatment where there is also some evidence of a negative effect of increased levels of stress and IVF success Thiering et al.
A randomized controlled trial of 60 couples attending a Turkish Hospital for their first IVF treatment Terzioglu, found a statistically significant association between providing counselling and support to couples and increased pregnancy rates.
A nurse who worked closely with the couples throughout the most stressful periods provided the intervention. The nurse gave couples detailed information about their treatment, made daily contact with the couple from the commencement of stimulation until embryo transfer and was present at oocyte collection and embryo transfer.
Standard care was provided to the control group. Three standard psychological tests were used to collect data at the beginning of the treatment cycle and 4—5 days after embryo transfer. Effects of counselling and support on ART pregnancy rates. Republished from Terzioglu with permission. There have been several observational studies to assess stress levels and associations with treatment outcome.
An association between stress levels prior to a treatment cycle and treatment outcomes was found Klonoff-Cohen et al. This study examined the effect of different types of stress on a range of outcome measures including oocytes retrieved, fertilization, pregnancy and live birth.
Stress was assessed using standardized psychological tests that were administered prior to treatment and during treatment. The chance of pregnancy and live birth delivery was decreased with increasing stress measures. The number of oocytes fertilized also decreased with increased stress.
A prospective study conducted in Belgium of 98 women undergoing IVF used standardized psychometric questionnaires administered prior to commencement of the treatment cycle to assess depression and coping skills Demyttenaere et al. The study found an increase in negative emotions in the group that did not become pregnant. A recent study of Danish couples Boivin and Schmidt, examined the effects of infertility-related stress on men and women and pregnancy after 1 year.
The data were controlled for potential confounders of age and length of infertility. A small increase in stress in women was associated with poorer treatment outcome, but not for men. Overall stress scores for women in the no success group were The small difference in means and wide scatter of the data may illustrate the difficulty of quantifying stress. A Dutch study attempted to use biochemical markers of stress during IVF treatment as well as reported stress Smeenk et al.
Higher levels of adrenalin were found at stressful time points in treatment oocyte retrieval and embryo transfer in women who did not become pregnant, compared with those who did become pregnant who also showed higher levels of noradrenalin at the time of embryo transfer. This study was blighted by missing data including the loss of urine samples. Several other studies have found stress to reduce pregnancy rates following ART treatment Thiering et al. Distribution of waiting time to first pregnancy TTP in months by coffee drinking habits and caffeine intake of women from Denmark, Germany, Italy, Poland and Spain, August to February Republished from Bolumar et al.
Other studies have found no relationship between the psychological status of women and the outcome of ART treatment Harlow et al. On balance, reported studies support an association between increased levels of psychological stress and impaired reproductive performance. The level of precision in determining a cause — effect relationship is low because the major measurements of stress are subjective and there is lack of consensus in defining and measuring stress levels.
The stimulant properties of caffeine have led to its widespread use as a beverage coffee, tea and soft drinks and some foods such as chocolate. Its consumption has been reported to prolong the time to pregnancy; although the mechanism for this is unclear, caffeine may affect female reproduction by targeting ovulation and corpus luteal function through alterations to hormone levels Klonoff-Cohen et al.
The consumption of caffeine has been associated with reduced fecundity in the general population. A prospective study of women attempting pregnancy found strong evidence of a reduced chance of pregnancy with increasing caffeine consumption Wilcox et al. The women were reviewed at enrolment and again at 3 and 6 months and their consumption of coffee, tea and soft drinks were recorded. The frequency of interviews allowed accurate recall of their caffeine consumption.
Daily information was also recorded regarding menstrual bleeding and intercourse until a pregnancy was confirmed. The data were adjusted for variables of age, frequency of intercourse, smoking, weight and age at menarche.
Women who consumed less than one cup of coffee were twice as likely to become pregnant compared with the moderate coffee drinkers, with the risk of failing to become pregnant increasing with higher consumption.
Most other studies rely on the collection of retrospective data after the period of caffeine consumption leaving them open to recall bias. After adjusting for potential confounders of age, smoking, the use of contraceptives and country, the risk of delayed conception with large amounts of caffeine consumption remained.
A study of pregnant women relied on interviews about their consumption of tea, coffee and cola between the time of conception and the date of interview Hatch and Bracken, The assumption was made that pre-pregnancy levels of caffeine consumption were consistent with levels during pregnancy.
However, with the achievement of pregnancy, women change many habits and caffeine consumption during pregnancy may not be the same as levels at the time of conception. Coffee aversion in pregnancy is frequently associated with nausea. Other potential confounding variables such as frequency of intercourse were not considered.
A study of women collected information about caffeine consumption coffee, tea and cola during the first month of pregnancy Stanton and Gray, Compared with non-smokers who did not consume caffeine, non-smoking women who drank more than three cups of coffee a day had a 2.
Predictably, smoking reduced the chance of pregnancy, but the effect of caffeine was only found in non-smokers. This study again makes the assumption that levels of consumption remain consistent before and during pregnancy, which may lead to misclassification.
This raises the possibility that caffeine consumption reflects a particular lifestyle that may include a number of confounding factors, of which smoking may be just one. There are also studies that have found no association between caffeine consumption and fecundity Joesoef et al.
Changes were integrated into each menstrual cycle by date of interview and averaged over the cycle. Caffeine consumption has also been associated with other causes of infertility including tubal factors and endometriosis Grodstein et al.
A meta-analysis Fernandes et al. However, not all studies have found an association between caffeine consumption and spontaneous abortion Mills et al. High levels of caffeine consumption during pregnancy has also been associated with an increased risk of stillbirth Wisborg et al. However, the concept of reverse causation due to unrecognized fetal problems may explain why women continued to drink large quantities of coffee during pregnancy.
The evidence leans towards an association between the consumption of caffeine particularly at high levels and reproductive performance, although most studies have relied on data being collected retrospectively which is subject to recall bias. There are fewer studies examining the effect of caffeine on the ART population. Doctor Recommended Vitamins and Supplements. The nutrients that a child consumes while growing up can affect the developing reproductive system.
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