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. - 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.
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 underweight 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.
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.
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.
How Are Workers and Their Babies Exposed?
Harmful substances can enter a woman’s body through - breathing in (inhalation), - contact with the skin, - or swallowing (ingestion). Pregnant workers and those planning to become pregnant should be especially concerned about exposure to reproductive hazards. Some chemicals (such as alcohol) can circulate in the mother’s blood, pass through the placenta, and reach the developing fetus. Other hazardous agents can affect the overall health of the woman and reduce the delivery of nutrients to the fetus. Radiation can pass directly through the mother’s body to harm her eggs or the fetus. Some drugs and chemicals can also pass through a mother’s body into the nursing baby through the breast milk. However, breast feeding has many positive effects. Thus a woman who may be exposed to reproductive hazards on the job should consult with her doctor or other health care provider before deciding whether or not to breast feed. Reproductive hazards do not affect every woman or every pregnancy. Whether a woman or her baby is harmed depends on how much of the hazard they are exposed to, when they are exposed, how long they are exposed, and how they are exposed.
How Are Families Exposed?
Workplace substances that affect female workers and their pregnancies can also harm their families. Without knowing it, workers can bring home harmful substances that can affect the health of other family members—both adults and children. For example, lead brought home from the workplace on a worker’s skin, hair, clothes, shoes, tool box, or car can cause lead poisoning in family members, especially young children.
How Can Exposures Be Prevented?