Infertility In Women

Description

Alternative Names

Risk Factors

In the US, an estimated 10.2% of women between the ages of 15 to 44, or about 6.2 million women, have impaired fertility, and the incidence is increasing. About 25% of women experience some period of infertility during their reproductive years. Between 1982 and 1988 there was a 37% increase of infertile women between the ages of 35 to 44. The number of infertile women is expected to reach 6.3 million in the year 2000, and may be as high as 7.7 million in 2025.

Age

As a woman ages, her chances for fertility decline. Infertility in older women appears to be mostly due to a higher risk for chromosomal abnormalities that occur in her eggs as they age. Older women are also more likely to have health problems that may interfere with fertility. If fertilization occurs, older, healthy women can usually successfully bear a fetus to term, although they have a higher risk for miscarriage. Using population studies, experts have come up with estimated odds for pregnancy at different ages, given no fertility intervention. A 2002 analysis of pregnancy rates based on conception on the day of ovulation suggested that women between ages 19 to 26 have twice the pregnancy rates as those between 35 and 39.

Weight Factors and Excessive Exercise

Although most of a womans estrogen is manufactured in her ovaries, 30% is produced in fat cells by a process that transforms circulating adrenal male hormones into estrogen. Because a normal hormonal balance is essential for the process of conception, it is not surprising that extreme weight levels, either high or low, can contribute to infertility.

Being Overweight. Being overweight or obese (fat levels that are 10% to 15% above normal) can contribute to infertility in various ways. Obesity is highly associated with polycystic ovarian syndrome (PCOS), which is cause of infertility in some cases. In one 2003 study, overweight women without PCOS were classified in one of five grades, depending on the severity of the obesity. The risk for irregular or absent periods increased two-fold by each increase in grade. In this group, amenorrhea (absent periods) was also highly associated with type 2 diabetes and blood sugar abnormalities.

Being Underweight. Body fat levels 10% to 15% below normal can completely shut down the reproductive process. Women at risk include the following:

• Women with eating disorders, such as anorexia or bulimia.
• Women on very low-calorie or restrictive diets are at risk, especially if their periods are irregular.
• Strict vegetarians might have difficulties if they lack important nutrients, such as vitamin B12, zinc, iron, and folic acid.
• Marathon runners, dancers, and others who exercise very intensely. (Lower body fat contributes to menstrual irregularities in competitive athletes, but other mechanisms are also involved.)

Lifestyle Factors

Smoking. Women who smoke one or more packs a day and those who started smoking before the age of 18 are at greater risk for infertility. Smoking also increases the risk for still births and low birth-weight babies. Male smokers also endanger fertility. Men who smoke have poorer sperm quality than nonsmokers, and they also have lower sex drives and have sex less frequently than nonsmokers. Heavy marijuana smoking appears to adversely affect fertility in both males and females.

Caffeine. A correlation has been found between caffeine consumption and infertility, possibly because has estrogen-like effects. Caffeine is found not only in coffee but also in tea, many soft drinks, chocolate, and a number of common medications.

Alcohol. Even moderate alcohol intake (as little as five drinks a week) can impair conception and also have adverse effects on the developing fetus.

Vaginal Douching. Vaginal douching can impair fertility and cause a number of gynecological problems. Studies suggest that it may contribute to infection, pelvic inflammatory disease, low-birth weight babies, preterm birth, and tubal pregnancy.

Sexual Practices. Sexual practices such as having multiple partners, not using condoms, and having intercourse during a period increase the risk for sexually transmitted organisms that can cause pelvic inflammatory disease leading to infertility.

Environmental Risks

Hormone-Disrupting Chemicals. Of particular concern is exposure to the following environmental hazards that might affect fertility. Estrogen-like chemicals or those that disrupt hormones are of particular concern for infertility in men and for effects on offspring women. Some being studied include the following:

• Diethylstilbestrol (DES), an estrogen compound, was used by some pregnant women in the 1940s and 1950s. The daughters of these women face a higher risk for cervical cancer, genital tract abnormalities, and miscarriage. However, DES does not appear to harm their granddaughter's reproductive capabilities.

The development of cervical cancer is gradual and begins as a pre-cancerous condition called dysplasia. It is usually a slow-growing cancer and if caught early can be successfully treated. Routine Pap smears can detect early changes in the cells of the cervix allowing cervical cancer to be caught early.

• Bisphenol A is a widely used chemical found in plastic food containers and bottles that has provoked concern. It has potent estrogen-like effects in low dose. Use of the chemical in female rats has produced prostate abnormalities in their male offspring. However, it is not clear how such animal studies relate to people.
• Phthalates, chemicals used to soften plastics, are under particular scrutiny for their ability to disrupt hormones. Specific phthalates of special concern include dibutyl phthalate (DBP) and others found in many products, including cosmetics and clay products sold to children (Fimo, Sculpey). Animals exposed to phthalates have significantly impaired sperm count and abnormalities in reproductive structures, such as the testes. In addition, there is some concern that exposure in pregnant women may affect the offspring.
• Exposure to pesticides has caused known reproductive problems in animals and birds. Pesticides with estrogen-like effects include DDT, aldrin, dieldrin, PCPs, dioxins, and furans.
• There has been some concern that plant-based estrogens (phytoestrogens), such as the isoflavones found in soy and other foods, may reduce fertility rates. Sheep and quail grazing on plants containing phytoestrogens have had lower fertility rates. Studies to date on women who eat soy products have largely reported only positive health benefits and no effects on fertility but more research is required.
• Most evidence on the hormone of chemical estrogens has been reported in animals and birds. Tests of single chemicals containing estrogen have reported little danger for people. Some studies, suggest, however, that exposure to more than one of these chemicals may be very harmful. At this time, there is no strong evidence supporting a serious harmful effect in people who have normal exposure to these chemicals. Major efforts are underway to determine the extent of any possible harm from them.

Exposure to Electromagnetic Waves or Microwave Emissions. Heavy exposure to electromagnetic wave or microwave emissions has been linked to some reduced fertility in men. Although it is difficult to prove any risk on a developing fetus, research is very reassuring about ordinary exposure to low level emissions, such as those produced by small appliances.

Stress and Fertility

Similar neurotransmitters (chemical messengers) act in the hypothalamus gland, which controls both reproductive and stress hormones. Severely elevated levels of stress hormone can, in fact, shut down menstruation. Whether stress has any significant effect on fertility is unclear. There is some modest evidence that stress can affect the outcome of fertility treatments. One interesting small study reported a significantly higher incidence of pregnancy loss in women who experienced both high stress and prolonged menstrual cycles. Studies on any association between infertility and job stress have been inconclusive.

Click the icon to see an image of the hypothalamus.