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FERTILITY

The Effect of Lifestyle on Fertility

Jayme S. Bosler, MD; Halina Wiczyk, MD

Common Clinical Scenario: Nancy is a 34-year-old nulligravida who comes to you because she has been trying to get pregnant for 18 months. When asked about her lifestyle, she admits to smoking half a pack of cigarettes per day, exercising 90 minutes every day, and eating a significant amount of junk food. Her BMI is 18. She hasn’t had regular periods, nor does she get PMS symptoms. Her husband, a truck driver, smokes a pack per day, drinks alcohol every night, and smokes marijuana.

Many couples find, to their surprise, that it can be difficult to get pregnant once the decision has been made to start trying. Most assume that once they stop their method of contraception, pregnancy will occur. This is not the case for more than 5 million women in the United States.1 Before medical interventions are considered, changes in lifestyle can improve the chances of conception. Couples trying to conceive may be encouraged to know that improving their nutrition, recreational habits, and stress levels can decrease their time to pregnancy. Simply choosing a healthier lifestyle can improve their chances.

DIET

Women whose diets include greater amounts of vegetables, fruits, and whole grains have been shown to have the highest chances of fertility. Those with the highest fertility rates eat less trans fat and sugar from carbohydrates, more protein from vegetables than animals, more fiber and iron, and more high-fat dairy products.2 Women who followed these diet strategies had a 6-fold difference in ovulatory fertility than those who did not.2

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CAFFEINE

Heavy caffeine intake has been shown to increase rates of infertility. Women who drink more than 6 cups of coffee or tea a day are 1.5-fold more likely to be infertile.3 The exact mechanism is unknown, but several pathways are possible. Caffeine consumption is inversely correlated to estradiol in pregnant women and positively correlated to levels of sex hormone binding globulin (SHBG). It is also correlated to decreased levels of prolactin and may inhibit ovulation or corpus luteum function.1

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ALCOHOL

Some studies show drinking alcohol in moderation does not have a statistically significant impact on fertility. One study showed that moderate alcohol consumption in women (7 to 8 drinks/week) is associated with reduced fertility and increased risk of spontaneous abortion.3 The effect of alcohol on fertility might be related to hormonal and ovulatory abnormalities. Current evidence is inconclusive regarding how much alcohol consumption may be safe during pregnancy.4 Of note, heavy alcohol use in men (>20 drinks/week) has shown a 2-fold increase in the time to pregnancy.3

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SMOKING

Cigarette smoking (both active and passive) has been proven to have an adverse impact on fecundity. Chemicals in cigarette smoke appear to accelerate follicular depletion and loss of reproductive function, affect the follicular microenvironment, and alter hormone levels in the luteal phase.4,5 Smoking results in chromosomal and DNA damage to human germ cells. Smoking also decreases sperm production, motility, and morphology in men. Cigarette exposure is associated with decreased gamete quality, impairment in fertilization, and early miscarriage. The vasoconstrictive and antimetabolic properties of nicotine, carbon monoxide, and cyanide may lead to placental insufficiency and embryonic and fetal growth restriction and demise. Smoking seems to be dose-dependent, with women who are heavy smokers (>15 cigarettes/day) having a 2-fold increase in time to pregnancy above nonsmoking women. Men who smoke have 1.4 times the risk for subfecundity than nonsmokers.3

Smoking marijuana, a type 1 cannabinoid receptor agonist, also impacts fertility. Fatty acid amide hydrolase (FAAH) activity and expression are mediated by type 1 cannabinoid receptors. FAAH controls several steps of sperm biology, from motility to capacitation and acrosome reaction. Therefore, concerns are raised regarding the use of marijuana and defective FAAH being linked to reduced reproductive potential.6

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EXERCISE

Regular exercise in moderation is essential for good health; excessive exercise in women can stop their periods and make them anovulatory.7 However, exercise does increase insulin sensitivity, which improves ovarian function and the chance of conception.4 A sedentary life has a negative impact on health; for men, it can decrease the sperm count. The sedentary lifestyle not only relates to exercise but also activities of daily life; men who have occupations that necessitate increased amounts of sitting have increased scrotal temperature. The testes need to be 3°C to 4°C cooler than core body temperature to maximize sperm production.8 Therefore, men who sit for prolonged periods have lower sperm counts and thus decreased fertility. Men who are attempting conception should avoid hot tubs, saunas, and excessive bike riding, due to increases in testicular temperature.9

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WEIGHT

Weight is a factor in fertility, although, like exercise, it is one with a bimodal effect. Women who are underweight (BMI <19 kg/m2) often are anovulatory due to decreased production of gonadotropin-releasing hormone (GnRH), and therefore they have gonadotropin concentrations that are too low to sustain ovarian function.8 The decreased GnRH may be due to decreased circulating levels of leptin, a hormone in fat cells. Insulin also plays a role in reproduction. Increases in insulin result in decreased levels of SHBG. With less binding globulin, the free (biologically active) levels of estrogen and androgens increase. Insulin resistance is a problem in many overweight females, especially those with truncal obesity and polycystic ovary syndrome (PCOS). Overweight women (BMI ≥25 kg/m2) and those with PCOS produce more insulin, which leads to an increase in androgen and subsequently impedes ovulation.10 Overweight women have both increased insulin and leptin, and therefore a preferential increase in luteinizing hormone (LH) but not follicle stimulating hormone (FSH). This, along with the free androgens, leads to stimulation of partial follicles that rarely ovulate.8 A majority of obese women (BMI ≥30 kg/m2) can start ovulating again with a 5% to 10% weight loss.11

Excess weight also has an adverse effect in men. Obese men have a higher incidence of oligozoospermia and asthenospermia. Androgens are aromatized to estrogen in the peripheral fat, suppressing gonadotropin concentrations by negative feedback.11 Obesity profoundly and adversely impacts overall health and, in particular, vascular health, by increasing proinflammatory factors and altering endothelial function and the androgen endocrine milieu, thus increasing the risk for erectile dysfunction as well.12

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STRESS

Although it is difficult to clearly define and measure psychologic stress, it has been implicated in lowering reproductive performance. One study of in vitro fertilization treatments showed that “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.”4 Some techniques to decrease stress, including cognitive behavioral therapy, support groups, and acupuncture, have been shown to improve pregnancy rates.4,13 Researchers do not fully understand how acupuncture works. It might aid the activity of the body’s pain-killing chemicals, β-endorphins. These normalize the secretions of GnRH, FSH, LH, estrogen, and progesterone. It also might affect the release of chemicals that regulate blood pressure and flow.13 Relaxation techniques using yoga and massage can also reduce the stress related to conception difficulties.

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CONCLUSION

Some lifestyle factors, such as smoking and weight, show conclusive evidence of their negative impact on fertility; studies on the effects of caffeine, alcohol, exercise, and stress during conception are not as conclusive (Table). Most couples having difficulty conceiving are eager to improve their chances. On the other hand, asking someone to change his or her lifestyle is a daunting request. Lifestyle variables do not explain absolute sterility but can have a profound effect on fertility. In general, if couples lead an overall healthy lifestyle, they could reduce their subfecundity by more than 50%.3 In turn, they could create a healthier environment for their future child.

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TABLE. Lifestyle Factors and Effects on Fecundity

Answer to question posed in clinical scenario above: When counseling the above couple, smoking cessation would be one of the first things to address. Nancy would benefit from eating a healthy diet and exercising somewhat less, which would help normalize her periods and, therefore, resume her ovulatory cycles. Her partner should stop smoking marijuana and limit alcohol consumption. Taking frequent breaks from the prolonged sitting required in his job may also be beneficial.

The authors report no actual or potential conflicts of interest in relation to this article.

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Jayme S. Bosler, MD, is Resident, and Halina Wiczyk, MD, is Associate Professor, both in the Department of Obstetrics and Gynecology, Baystate Medical Center, Tufts University School of Medicine, Springfield, MA.

References

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3. Hassan MA, Killick SR. Negative lifestyle is associated with a significant reduction in fecundity. Fertil Steril. 2004;81(2):384-392.
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8. Sharpe RM, Franks S. Environment, lifestyle and infertility—an inter-generational issue. Nat Cell Biol. 2002;4 Suppl:S33-S40.
9. Storck S, reviewer. Infertility in men. New York Times. Reviewed December 29, 2008. Available at: http://health.nytimes.com/health/guides/disease/infertility-in-men/overview.html. Accessed October 20, 2009.
10. Mathews ES. Lifestyle and infertility. Bolo. July 22, 2007. Available at: www.boloji.com/wfs5/wfs949.htm. Accessed October 20, 2009.
11. Practice Committee of American Society of Reproductive Medicine. Obesity and reproduction: an educational bulletin. Fertil Steril. 2008;90(5 Suppl):S21-S29.
12. Feeley RJ, Traish AM. Obesity and erectile dysfunction: is androgen deficiency the common link? ScientificWorldJournal. 2009;9:676-684.
13. Paulus WE, Zhang M, Strehler E, El-Danasouri I, Sterzik K. Influence of acupuncture on the pregnancy rate in patients who undergo assisted reproduction therapy. Fertil Steril. 2002;77(4):721-724.

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