Infertility

I

Introduction

Infertility, inability to conceive or carry a child to term. According to the Centers for Disease Control and Prevention (CDC), infertility affects about 6 million American women and their partners. People who suffer from infertility can seek medical advice to identify the cause of infertility and undergo treatment. More than half of those who seek treatment eventually conceive and carry a pregnancy to full term.

Conceiving a baby through sexual intercourse involves many steps. For conception to occur, a man’s sperm, produced in his testes, must fertilize a woman’s egg, produced in her ovaries. During sexual intercourse, sperm from the man are ejaculated (ejected during orgasm) deep inside the woman’s vagina. The sperm travel into the uterus and up the fallopian tubes (channels connecting the ovaries to the uterus), where the sperm meet the egg. If a sperm is able to penetrate, or fertilize, an egg, and if other conditions are favorable, the fertilized egg will travel from the fallopian tube to the uterus, where it implants in the uterine lining. Fetal development then begins (see Human Sexuality).

II

Causes of Infertility

A problem or obstruction at any point during conception prevents pregnancy from taking place. For about a third of infertility cases, either physicians can find no cause, or the cause can be traced to conditions in each partner that interact to cause infertility. About a third of cases can be traced to causes specifically in the male, and about a third to causes in the female.

A

Conditions Affecting Both Partners

A number of factors that affect males and females alike can increase the risk of infertility. Perhaps the most common problem is age—the older a person is, the more difficult it is to become pregnant. Over the last 20 to 30 years there has been a trend to delay childbearing, often until women are in their 30s. A woman reaches her peak fertility at age 18 or 19, with little change until the mid-20s. As she approaches age 30, her hormone levels start to decline and her fertility also begins a slow decline, with a more rapid decline after age 35. Menopause, which occurs in the late 40s to early 50s in most women, marks the end of a woman’s natural ability to bear children. A man’s fertility decline is not as rapid and has no clear-cut end point, but a man of 50 has lower hormone levels and is likely less fertile than he was at age 25 or 30.

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Genetics can also play a role in infertility. An irregular genetic makeup in one or both partners can prevent conception or result in a miscarriage, the spontaneous abortion of a fetus. Up to 60 percent of miscarriages that occur in the first three months of pregnancy result from genetic abnormalities.

Sexually transmitted infections (STIs) are a leading cause of infertility. In many cases, diseases such as gonorrhea and chlamydia may have no symptoms. If left untreated, STIs can cause extensive and irreparable damage to reproductive organs. In women, untreated STIs can cause pelvic inflammatory disease (PID), a bacterial infection that damages the uterus, fallopian tubes, and ovaries. PID is one of the primary causes of ectopic pregnancy, a life-threatening condition in which the fetus begins to develop in the fallopian tube. In men, untreated STIs can result in sterility, an inability to conceive.

In recent years fertility experts have determined that in some cases the immune system may play a role in preventing conception or interfering with embryo implantation in the uterus. Both men and women can develop an allergic reaction to sperm, causing their bodies to create antibodies that attack and kill sperm. These sperm antibodies may also bring about infertility by causing sperm to clump together, preventing them from fertilizing an egg.

B

Male Infertility Factors

Historically men were assumed to be fertile if they were capable of sexual intercourse. As a partial consequence of this attitude, research on fertility has traditionally emphasized problems in women. More recently, however, physicians have found that the male partner is the primary cause of infertility in about 30 percent of cases. Causes of male infertility can be categorized into sperm abnormalities, structural problems, or medical disorders.