Lifestyle Factors and Female Fertility
A number of studies have shown conclusively that lifestyle can affect infertility including age, being excessively underweight or overweight, alcohol or smoking. These five lifestyle factors are discussed below. (There is further information regarding lifestyle factors and male fertility in the webpage Causes of Infertility>Lifestyle Factors and Male Fertility on this website.)
INFERTILITY AND AGE
Peak fertility for women is reached in their 20s and this starts to decline in the early 30s. It has been well known for some time that women over 37 years of age have dramatically decreased fertility, however new studies have shown that males after 40 years old have a 50% decrease in fertility rates.
Ovarian reserve and age
All the eggs a woman will ever have are formed in the first weeks of life. From the start of puberty eggs are lost in every menstrual cycle until they are eventually all used up and the ovary ceases to function. This is called menopause. The use of the oral contraceptive pill does not prevent or slow this monthly egg loss. It is thought that as the woman ages the oocytes in her ovaries accumulate chromosomal defects called aneuploidies. A common aneuploidy is Downs Syndrome, which is much more common for pregnancy if the mother is 38 or older.
Aneuploidies are not the only factors affected by maternal age as the uterus also becomes less receptive to pregnancy with age. This represents a natural decline with age and there is no known way of rejuvenating either the ovary or the uterus. This results in a marked decline in IVF success rates as the age of the group increases past 38 years.
WOMEN WHO ARE EXCESSIVELY UNDERWEIGHT
Excessively thin patients have greatly increased irregularity of menstrual cycles, and consequently reduced conception and birthing rates than women in the normal weight range. Furthermore, if an underweight woman conceives, there may be adverse effects during pregnancy on the foetus. For instance, mothers who hunger or are underweight during:
• the 1st trimester of pregnancy have a higher risk of delivering offspring who show the effects of obesity;
• the 2nd trimester of pregnancy are more likely to deliver prematurely; and
• the 3rd trimester of pregnancy have a higher risk of producing offspring who develop insulin resistance and diabetes.
WOMEN WHO ARE EXCESSIVELY OVERWEIGHT
Excessively overweight women also have greatly increased irregularity of menstrual cycles, and consequently reduced conception and birthing rates than women in the normal weight range. Studies have shown that even being 10kg overweight can result in a 10% loss of fertility.
Obese patients have a 4 fold risk of foetal death and 27% increased chance of miscarriage. Increased risk of complications to the mother during pregnancy related to being overweight include an increased chance of post date deliveries resulting in an increased rate of labour inductions and Caesarian births. Overweight mothers are also at greater risk of high blood pressure and venous thrombosis during pregnancy and of haemorrhage during birth. Furthermore, babies born to overweight mothers have shown to have a significantly increased risk of developing diabetes in infancy.
However, the good news is that the chance of fertility recovery is 8% in overweight patients after three months of slight but continual weight loss. For obese patients, the chance of fertility recovery is 18% after continual light weight loss; however it will usually take 9 months longer to conceive than for women in the healthy weight range.
SMOKING, INFERTILITY AND HEALTH CONCERNS
It has been shown that parents’ smoking causes infertility and health problems for up to four future generations. For instance, it is thought to have an impact on endometriosis over generations of women. Smoking has also been shown to be the primary cause of tubal damage in both males and females thereby resulting in infertility. Also, if a non-smoking female has a child with a smoking-male, that child has a five fold increased chance of developing childhood cancer or leukemia.
ALCOHOL AND FERTILITY
While there is no clear evidence that moderate alcohol consumption (up to 10 standard drinks per week – no more than 2 per day) has any adverse effect on fertility, heavy alcohol use probably reduces female fertility and certainly reduces sperm count and quality with an increase in sperm abnormalities and reduction in fertilising ability.