Reproductive and Birth Outcomes and the Environment

Our understanding of risk factors for reproductive problems such as infertility, low birth weight, prematurity, fetal and infant death has increased over the past decades. Certain health conditions, social and economic factors, and behaviors can increase the risk of adverse reproductive and birth outcomes. We have also learned that environmental exposures can play a role in reproductive and birth outcomes. However, there is still much we do not know.

Exposure and Risk

The following are some of the possible environmental exposure and risk factors that are associated with reproductive and birth outcomes:

• Exposure of nonsmoking pregnant women to environmental tobacco smoke (also known as secondhand smoke) may be a risk factor for preterm birth, low birth weight, and possibly fetal death or miscarriage. Read more about premature births.
• Exposure to air pollution may be related to both low birth weight and preterm birth, even at low levels.
• A pregnant woman's exposure to lead may cause preterm birth, low birth weight, and spontaneous fetal death or miscarriage. Read more about lead exposure during pregnancy.
• Exposure to pesticides has been associated with fetal death (miscarriage) and babies being born too small, but more research is needed in this area. Read more about pesticides and pregnancy.
• Although age and certain health conditions are more commonly associated with infertility, it is believed that environmental contaminants may cause infertility by creating other health conditions. For example, some research suggests that environmental contaminants can affect a woman's menstruation and ovulation. Low-level exposures to compounds such as phthalates, polychlorinated biphenyls (PCBs), dioxin, and pesticides are suspected risk factors. Much more research needs to be done to find out how environmental contaminants may be affecting human fertility. Learn more about fertility and infertility.
• Some scientists have suggested that environmental hazards can affect how many males are born. Parents and the fetus can be exposed to different hazards referred to as endocrine disruptors. Fewer males are conceived when exposure to endocrine disruptors causes a decrease in testosterone. Diethylstilbestrol (DES), a synthetic estrogen widely prescribed to pregnant women during the mid-1900s, is a strong endocrine disruptor. Previous studies have suggested an association between endocrine-disrupting compounds and the secondary sex ratio (the sex ratio of the grandchildren of the exposed women). Several studies show that declines in the sex ratio of males to females at birth may be associated with occupational exposure, or exposure to air pollution.Read more about endocrine disruptors.

Prevention

Women who are pregnant or may become pregnant should follow their doctor's advice on how they can have a healthy baby. Doctors can also answer questions on fertility and give advice on conceiving. Early and regular prenatal care helps identify conditions and behaviors that can result in adverse reproductive and birth outcomes.

Here are some ways to prevent environmental exposures:

• Stop smoking and avoid secondhand smoke.
• Limit outdoor activity when the Air Quality Index shows unhealthy levels of air pollutants.
• Cut out or reduce any indoor sources of particulate matter, like wood-burning stoves and fireplaces, and try to reduce the amount of time spent outdoors near areas with higher levels of air pollution, such as areas with a lot of traffic.
• Stay away from lead.
• Stay away from mercury. Some fish, especially albacore tuna, may have been contaminated with mercury. State health departments send out public fish consumption guidelines that pregnant women can follow.
• Do not use pesticides if you are pregnant. Stay away from rooms that have been recently sprayed with insecticides and from other areas with potential pesticide exposure.