One in six couples suffer infertility, defined as the inability to conceive a pregnancy after 12 months of unprotected sexual intercourse. Infertility is attributed to male and female factors including ovulatory disorders, ageing, endometriosis, fallopian tube damage, uterine fibroids, autoimmune disorders plus lifestyle and environmental factors including geographical challenges such as fly-in-fly-out working.
Diet and exercise
A healthy body mass index is beneficial for fertility. A BMI below 18 or above 25 may impact fertility by interfering with hormonal and metabolic mechanisms.
Increased abdominal fat distribution reduces ovulation and reduces the chance of conception even when ovulation occurs. BMI above 30 is associated with a halving in spontaneous conception rates and exacerbation of the adverse metabolic and reproductive issues seen in women with polycystic ovarian syndrome (PCOS).
Endocrine abnormalities and lower testosterone rates are also seen in obese men, as is erectile dysfunction, which can impact on coital frequency and semen parameters.
Obesity contributes to poorer outcomes with IVF including lower rates of pregnancy and higher rates of miscarriage. Obesity in pregnancy increases the risk of gestational diabetes, hypertensive disorders in pregnancy, preterm birth, fetal macrosomia, and higher rates of caesarean section.
The child’s health is also impacted. Obesity increases rates of congenital anomalies (e.g. neural tube defects, orofacial clefts, cardiovascular anomalies), and childhood obesity. Weight loss medications and insulin sensitising agents as well as bariatric surgery have been used by women attempting to lose weight to improve reproductive outcomes. Early dietician, exercise physiologists and psychologist review should be encouraged.
A diet rich in antioxidants, fibre, folate, fruit and vegetables for both men and women can improve fertility. Women with higher monounsaturated to trans-fat ratio, vegetable over animal protein, high-fat over low-fat dairy, a decreased glycaemic load, and an increased intake of iron and multivitamins had lower rates of infertility due to ovulation disorders.
Advise a folic acid supplement (minimum 400mcg daily) to reduce neural tube defects risk and avoid heavy seafood consumption due to the negative impact of high mercury levels on fertility. For men specifically, excess levels of oxidative free radicals can affect sperm motility and DNA damage and a diet low in fat and high in protein has been shown to improve overall health, enhancing fertility.
Moderate physical activity positively impacts fertility by optimising energy balance in the body and improves physical wellbeing and mood. Excessive exercise may result in low levels of leptin secretion from adipocytes as a consequence of reduced energy intake or excessive energy use. This down regulates the hypothalamic pituitary ovarian axis, which controls ovulation.
It is essential to take a history from women with lower body mass indexes to determine whether amenorrhoea or oligomenorrhoea may be due to this phenomenon as a reduction in energy expenditure and relaxation of any rigid dietary restrictions in place may aid in resumption of normal ovulation. Creating new coping strategies for women who rely on exercise for stress management may aid in long-term stress management and the creation of alternate methods to manage stress. Encourage moderately strenuous activities (e.g. pilates, yoga, walking, swimming) three to four times a week.
Substances
Smoking negatively impacts fertility in men and women. Women who smoke are twice as likely to have infertility and the impact is dose dependent even in women who are passive smokers. Oocytes and sperm are susceptible to the effects of cadmium and cotinine found in cigarettes.
Tetrahydrocannabinol (THC) found in cannabis has also found to decrease gonadotropin-releasing hormone (GnRH) secretion by the hypothalamus with concomitant decreases in folliculogenesis, ovulation and sperm maturation and function. Heroin, cocaine, and abuse of codeine also reduce reproductive performance.
Direct links between alcohol consumption and testicular atrophy, decreased libido and decreased sperm count have been demonstrated.
It is thought that alcohol affects female reproductive function by reducing estrogen levels, which reduce FSH and suppress both folliculogenesis and ovulation. The amount of alcohol that impacts on reproductive function is difficult to ascertain and abstaining when trying for a pregnancy is recommended. Alcohol consumption in women has been associated with earlier menopause due to accelerated follicular depletion, increased time to conception, reduction in conception rates by 50%, reduced implantation and increased risk of miscarriage and fetal death.
Consumption of 500mg (over five cups of coffee a day) has been associated with decreased fertility in women. Two to three cups of coffee per day (200-300mg) may increase miscarriage risk but has not been shown to increase the risk of congenital anomalies.
Recent findings showed maternal caffeine consumption is reliably associated with major negative pregnancy outcomes such as miscarriage, stillbirth, low birth weight, childhood acute leukaemia and childhood overweight and obesity. Current evidence supports advising pregnant women and women contemplating pregnancy to avoid caffeine.
Environmental (specifically endocrine-disrupting) chemicals can alter hormonal function of men and women. Advise avoidance of exposure to polychlorinated biphenyls and strongly encourage use of personal protective equipment when exposed to pesticides or chemicals. Limiting exposures to personal care products and air pollution can improve female fertility.
Perhaps the most modifiable factor is the age at which a couple consider trying for a pregnancy. Fertility declines with increasing age of both the man and woman, but the effects are greater in women.
The age-related decline in pregnancy and live birth is coupled with an increased risk of aneuploidy and miscarriage. Semen parameters in men decline after the age of 35 and offspring born to men over 40 have increased risks of birth defects, schizophrenia, and cancer.
Key messages
- One in six couples suffer infertility
- Many lifestyle factors impact fertility and can be improved
- Age is an overlooked modifiable factor.
– References available on request
Author competing interests – nil