What Reproductive Hazards Might Be Caused by Workplace Exposures?

Only a few substances (some viruses, chemicals, and drugs) are known to cause reproductive health problems. Scientists are just beginning to discover how workplace exposures might cause reproductive problems. The following problems may be caused by workplace exposures:

  • Menstrual cycle effects
  • Infertility and subfertility
  • Miscarriage and stillbirths
  • Birth defects
  • Low birth weight and premature birth
  • Developmental disorders
  • Childhood cancer

Each problem is discussed in more detail in the following sections.

Menstrual Cycle Effects

High levels of physical or emotional stress or exposure to chemicals such as carbon disulfide may disrupt the balance between the brain, pituitary, and ovaries. This disruption can result in an imbalance of estrogen and progesterone, and lead to changes in menstrual cycle length and regularity and ovulation. Because these sex hormones have effects throughout a woman's body, severe or long-lasting hormone imbalances may affect a woman's overall health.

Infertility and Subfertility

About 10% to 15% of all couples are unable to conceive a child after 1 year of trying to become pregnant. Many factors can affect fertility, and these factors can affect one or both partners. Damage to the woman's eggs or the man's sperm, or a change in the hormones needed to regulate the normal menstrual cycle are just a few things that can cause problems with fertility.

Miscarriage and Stillbirths

About 1 in every 6 pregnancies ends in a miscarriage-the unplanned termination of a pregnancy. Miscarriages can occur very early in pregnancy, even before the woman knows she is pregnant. Miscarriages and stillbirths occur for many reasons, such as the following:

  • The egg or sperm may be damaged so that the egg cannot be fertilized or cannot survive after fertilization (Infertility).

  • A problem may exist in the hormone system needed to maintain the pregnancy.

  • The fetus may not have developed normally.

  • Physical problems may exist with the uterus or cervix.

What causes most of these problems is still unknown.

Birth Defects

A birth defect is a physical abnormality present at birth, though it may not be detected until later. About 2% to 3% of babies are born with a major birth defect. In most cases, the cause of the birth defect is unknown. The first 3 months of the pregnancy is a very sensitive time of development because the internal organs and limbs are formed during this period. Many women are not aware that they are pregnant during much of this critical period.

Low Birth Weight and Premature Birth

About 7% of babies born in the United States are born underweight or prematurely. Poor maternal nutrition, smoking, and alcohol use during pregnancy are believed to be responsible for most of these cases. Although better medical care has helped many under- weight or premature babies to develop and grow normally, they are more likely than other babies to become ill or even die during their first year of life.

Developmental Disorders

Sometimes the brain of the fetus does not develop normally, which leads to developmental delays or learning disabilities later in life. About 10% of children in the United States have some form of developmental disability. Such problems are often not noticeable at birth. They can be difficult to measure, may be temporary or permanent, and range from mild to severe. Developmental problems may appear as hyperactivity, short attention span, reduced learning ability, or (in severe cases) mental retardation.

Childhood Cancer

Ionizing radiation has caused cancer in some children whose mothers were exposed during pregnancy. The current practice of minimizing the use of X-rays on pregnant women, the use of newer equipment that reduces the risk of exposure, and the use of protective shields have all helped to decrease the likelihood of harmful radiation exposure to fetuses.