Impact of Lifestyle Factors on Ovarian Function and Reproductive Health in Women

‘A record number of women are affected by what the WHO has termed ‘globesity’ at the same time infertility rates are escalating.’

Lifestyle factors play a crucial role in a woman's ability to conceive and maintain a healthy pregnancy. Women of all ages vary in their fecundability and fertility, and a major contributing factor to achieving a healthy pregnancy is maternal preconception health. Infertility rates are on the rise and affect an estimated 15% of couples in industrially developed countries [1]. Infertility is diagnosed if a couple is unable to achieve a pregnancy after 12 months of unprotected intercourse and spans a broad spectrum of conditions, including diagnoses such as ovulatory disorders, tubal disease, endometriosis, chromosomal abnormalities, sperm factors and unexplained infertility.

Mounting evidence has shown that maternal preconception weight can set the stage for conception and beyond. Many studies have reported a U-shaped effect of body mass, and women at either extreme experience endocrine and metabolic alterations that can affect their ability to ovulate and conceive. BMI is a measure of body weight and is calculated as weight (kg) divided by height² (m). Healthy- or normal weight individuals have a BMI in the range of 20–24.9 kg/m², while 25.0–29.9 kg/m² is overweight and 30 kg/m² and over is classified as obese. A record number of women are affected by what the WHO has termed ‘globesity’ at the same time infertility rates are escalating. The consequences of these health conditions are far-reaching and affect women of all ethnic groups, all ages and all educational and socioeconomic levels. The prevalence of processed or fried foods in the Western diet, coupled with an increase in sedentary behavior, has resulted in a staggering increase in the number of women who are overweight or obese. The obesity epidemic continues to compromise health, quality of life and the global economy. A growing body of research suggests that a diet high in fat may result in the accumulation of end products that mediate cellular damage within the ovary and may alter the microenvironment of the oocyte [2].

Increased body mass is an independent risk factor for a list of pregnancy-related pathologies, including early pregnancy loss before 6 weeks gestation and spontaneous abortion or miscarriage after 7 weeks gestation. These data hold true in overweight and obese women who conceived by natural means [3], as well as those who achieved pregnancy after undergoing assisted reproduction [4]. Many studies have sought to ascertain the mechanisms by which excess weight may result in an increased incidence of miscarriage in overweight and obese women, yet the exact cause remains unknown. Endocrine etiology is a contributing factor to recurrent spontaneous abortion in women of different BMIs in the general population who conceived naturally [5]. Gestational diabetes, increased likelihood of an operative birth and the presence of congenital malformations in the baby are also associated with maternal obesity.

Other lifestyle factors that have a deleterious effect on female fertility include smoking, caffeine and alcohol exposure. Cigarette smoking affects women at the level of their ovary, altering the follicular microenvironment and compromizing oocyte quality. There is evidence that the zona pellucida is thicker in smokers, which may make it more difficult for sperm penetration [6] and result in lower fertilization rates. Smokers have reduced uterine receptiveness, lower mean number of retrieved oocytes, higher miscarriage rates, as well as poorer implantation, ongoing pregnancy and livebirth rates [7]. There is also evidence that tobacco consumption accelerates ovarian aging, and the mean age of menopause in smokers is lower than in nonsmokers. Alcohol consumption is also related to hormonal and ovulatory abnormalities [8], although the level of consumption associated with risk is unclear. In addition to the possibility that alcohol has a direct effect on oocyte maturation, it has been hypothesized that alcohol may lead to elevated estrogen levels, thereby reducing FSH secretion and suppressing folliculogenesis and ovulation [9]. The consumption of caffeine has also been shown to negatively affect female fertility, possibly by targeting ovulation corpus luteal function through alterations in hormone levels [10]. A review of the literature suggests that the effects of smoking, alcohol and caffeine on fecundity appear to be dependent on the amount consumed and the duration of exposure [9].

‘Optimal preconception health is vital to achieving a healthy pregnancy and the best possible postnatal outcome for mother and baby.’

There are, of course, many confounding factors independent of lifestyle risk factors that are contributing to the rise in infertility rates. A leading factor is the upward shift in the age of women having children, which has garnered increased attention in recent years as more women postpone childbearing to climb the career ladder. In Australia, the median age of women at the time of birth in 2004 was 30.6 years and the highest fertility rate was in the 30–34-year age group and these figures are similar in other industrially developed counties. This is of increasing concern, as peak fertility in women has been reported to be at 22 years of age and begins to decline in the mid-to- late 20s [11]. Women over the age of 35 years experience a dramatic decline in fertility, and by the time a woman celebrates her 40th birthday, her fertility is a quarter of what it was at the age of 30 years. The incidence of genetic abnormalities and spontaneous abortion also increases with maternal age. In vitro fertilization success rates are also dramatically lower in women over the age of 38 years, a fact that is widely documented in the literature and supported by our clinical work.

The importance of promoting a healthy lifestyle among couples trying to achieve pregnancy cannot be underestimated and will benefit not only their general health, but may actually help to prevent subfertility. Couples trying to get pregnant are usually advised to abstain from smoking in addition to minimizing caffeine and alcohol consumption, which proves difficult or even impossible for many. Weight management involves striking a healthy balance between biology, behavior and environmental influences. In overweight or obese individuals, weight loss should be promoted as an initial treatment for infertility. It is the percentage of weight lost that is crucial and Huber-Buchholz et al. showed that a 2–5% reduction in body weight is associated with the restoration of ovulation, an 11% reduction in abdominal fat, a 4-cm reduction in waist circumference and a 71% increase in insulin sensitivity [12]. Although the most effective method for achieving and maintaining weight loss is controversial, it appears that a multipronged approach involving a combination of regular exercise, dietary management, cognitive–behavior therapy and a supportive group environment are key. A program called Fertility Fitness was instituted in our clinic in Adelaide, Australia, which incorporated these components and was met with great success. The program involved weekly dietetic and psychologic intervention, and participants were treated by a multidisciplinary team including an obstetrician/gynecologist, psychiatrist, dietician, fitness professional and nurse. Ovulation was restored in many previously anovulatory women after moderate weight loss, leading to a high spontaneous pregnancy rate [13,14].

‘The importance of promoting a healthy lifestyle among couples trying to achieve pregnancy cannot be underestimated, and will benefit not only their general health, but may actually help to prevent subfertility.’

Although the field of assisted reproduction has made great strides over the last 20 years, preconception health and lifestyle choices surpass all forms of reproductive technology as the factor of paramount importance for women trying to conceive. Optimal preconception health is vital to achieving a healthy pregnancy and the best possible postnatal outcome for mother and baby. With this knowledge, women will be empowered to make informed lifestyle choices, which, it is hoped, will result in a decline in the number of couples seeking fertility treatment.