Number 832 (Replaces Committee Opinion Number 575, October 2013)
Committee on Obstetric Practice
The American College of Nurse-Midwives endorses this document. This Committee Opinion was developed by the Committee on Obstetric Practice in collaboration with liaison member Nathaniel DeNicola, MD, MSc and committee member Ann E. Borders, MD, MSc, MPH, and with the assistance of Veena Singla, PhD and Tracey J. Woodruff, PhD, MPH.
ABSTRACT: There is emerging evidence that links exposure to toxic environmental agents and adverse reproductive and developmental health outcomes. Toxic exposures related to reproductive and developmental health primarily have been associated with infertility and miscarriage, obstetric outcomes such as preterm birth and low birth weight, neurodevelopmental delay such as autism and attention deficit hyperactivity disorder, and adult and childhood cancer. Although there is substantial overlap in the type of exposure and the associated health outcomes, for the purposes of this document, exposures generally can be grouped into the following categories: toxic chemicals, air pollution, and climate change-related exposures. Obstetric care clinicians do not need to be experts in environmental health science to provide useful information to patients and refer patients to appropriate specialists, if needed, when a hazardous exposure is identified. It is important for obstetrician–gynecologists and other obstetric care clinicians to become knowledgeable about toxic environmental exposures that are endemic to their specific geographic areas, such as local water safety advisories (eg, lead-contaminated water), local air quality levels, and patients’ proximity to power plants and fracking sites. Although exposure to toxic environmental agents is widespread across populations, many environmental factors that are harmful to reproductive health disproportionately affect underserved populations and are subsumed in issues of environmental justice. Clinical encounters offer an opportunity to screen and counsel patients during the prepregnancy and prenatal periods—particularly individuals most disproportionately affected—about opportunities to reduce toxic environmental health exposures. This Committee Opinion is revised to integrate more recent literature regarding reducing prepregnancy and prenatal toxic environmental exposures.
Recommendations and Conclusions
The American College of Obstetricians and Gynecologists makes the following recommendations and conclusions:
It is important for obstetric care clinicians to be knowledgeable about toxic environmental agents in relation to environmental health risk assessment, exposure reduction, and clinical counseling.
Obstetrician–gynecologists and other obstetric care clinicians should consider including questions about environmental exposures in the patient history during prepregnancy visits and prenatal care.
Typical elements of an environmental health history include assessment for exposures from the workplace, home, or recreational activities.
It may be beneficial to integrate environmental health into obstetrics and gynecology training and practice. Advocating for policies that will reduce harmful exposures and protect the health of pregnant individuals and their children is encouraged.
This Committee Opinion is revised to integrate recent literature regarding reducing prepregnancy and prenatal toxic environmental exposures. Scientific evidence has emerged over the past 20 years that demonstrates that prepregnancy and prenatal exposure to toxic environmental agents can have lasting effects on reproductive health across the life span 1 2 3 4 5. Although there is evidence that connects some exposures to effects on pregnancy and fetal health, more research is needed to explore other environmental exposures and guide recommendations for effective clinical interventions. Still, clinical counseling toward reduction, when possible, of exposures that are known or considered to be potentially toxic can be included in care while more evidence is gathered regarding the clinical efficacy of specific interventions and questions of causation.
Toxic environmental agents can range from population-based exposures such as air pollution and water contamination to specific individual exposures such as personal care products and food packaging 6. Exposures may be the result of an acute environmental crisis, such as the 2014 lead-contaminated water in Flint, Michigan. They also may result from chronic, often undetected, periods of continued pollution, such as the widespread mercury poisoning from methylmercury bioaccumulation in local fish and shellfish after decades of industrial wastewater being dumped in Minamata Bay, Japan 7. Notably, this environmental crisis laid the groundwork for global regulation on mercury pollution and identified seafood as a potential source of heavy metal exposure 7.
Unlike pharmaceuticals, most environmental chemicals have entered the marketplace without comprehensive and standardized information regarding their reproductive or other long-term toxic effects 8. Given that intrauterine gestation is a critical and particularly susceptible window of human development, obstetrician–gynecologists and other obstetric health care clinicians can be effective in reducing prenatal exposure to environmental health threats because they are uniquely positioned to educate patients about the effects of environmental exposure before and during pregnancy. Therefore, it is important for obstetric care clinicians to be knowledgeable about toxic environmental agents in relation to environmental health risk assessment, exposure reduction, and clinical counseling. Clinical encounters offer an opportunity to screen and counsel patients during the prepregnancy and prenatal periods—particularly individuals most disproportionately affected—about opportunities to reduce toxic environmental health exposures. The guidance in this document comes with the understanding that some individuals and communities may have limited control over such exposures and may need to balance competing risks; therefore, recommendations are intended to guide counseling on reducing exposure where possible and to advocate for policies that will protect all populations.
Although exposure to toxic environmental agents is widespread across populations, many environmental factors that are harmful to reproductive health disproportionately affect underserved populations and are subsumed in issues of environmental justice 9. In the United States, individuals in communities of color are more likely to live in counties with the highest levels of outdoor air pollution 10 11 and to be exposed to a variety of indoor pollutants, including lead, allergens, and pesticides, than white populations 12. In addition, the effects of exposure to environmental chemicals can be exacerbated by injustice, racism, poverty, neighborhood quality, housing quality, psychosocial stress, and nutritional status 12 13 14.
Individuals with occupational exposure to toxic chemicals are additionally vulnerable to adverse reproductive health outcomes because of the risk of higher exposures in the workplace 15. For example, levels of organophosphate pesticides and phthalates (often used in plastics) measured in occupationally exposed populations are far greater than levels measured in the general population 16 17. Immigrant populations working low-wage labor disproportionately work in occupations associated with a hazardous workplace environment in relation to toxic chemical exposures 18 19.
A 2009 report by the National Academy of Sciences underscores that the effects of low-dose exposure to an environmental contaminant may be quite different based on characteristics such as the underlying health status of the population and the presence of additional or background environmental exposure 20.
Environmental Exposures and Outcomes
There is emerging evidence that links exposure to toxic environmental agents and adverse reproductive and developmental health outcomes 4 21 22 23 24. However, more research is needed to understand whether these associations are linked to causality and, if so, to determine the levels of exposure to guide recommendations for clinical interventions. Toxic exposures related to reproductive and developmental health primarily have been associated with infertility and miscarriage, obstetric outcomes such as preterm birth and low birth weight, neurodevelopmental delay such as autism and attention deficit hyperactivity disorder, and adult and childhood cancer 25 Table 1. Although there is substantial overlap in the type of exposure and the associated health outcomes, for the purposes of this document, exposures generally can be grouped into the following categories: toxic chemicals, air pollution, and climate change-related exposures 6.
Chemicals can be found in a wide range of consumer products, personal care products, food packaging, and household materials, as well as in air and water 26. Chemicals can cross the placenta and, in some cases, such as with methylmercury, can accumulate in the fetus, which results in higher fetal concentrations than maternal levels 27 28 29. Prenatal exposure to specific toxic environmental chemicals is associated with various adverse neonatal and childhood health consequences, and exposure at any point in gestation may lead to harmful reproductive and developmental health outcomes. For example, scientific consensus among a group of expert scientists, health professionals, and patient advocates called Project TENDR (Targeting Environmental Neuro-Developmental Risk) identified toxic chemical exposures that may contribute to neurodevelopmental disorders, including learning disabilities, attention deficit hyperactivity disorder, autism, and behavioral or intellectual delay 4 30 Table 1 , Table 2.
Many of these exposures, particularly among the toxic chemicals, share a common biological pathway that results in endocrine disruption 31 32. These endocrine disrupting chemicals represent a heterogeneous group of agents used in pesticides, plastics, industrial chemicals, and fuels.
Emerging evidence finds that that air pollution, especially fine particulate matter (PM2.5, or fine inhalable particles with diameters that are generally 2.5 micrometers and smaller), may be associated with adverse fetal outcomes, including preterm birth 33 34 35 36 37 38 39 and low birth weight 33 39 40 41 42. Supporting intervention studies show that reducing air pollution exposure may reduce the risk of preterm birth, as has been reported in populations surrounding retired coal power plants 43. Proximity to fracking sites also has been associated with low birth weight 44.
Climate Change and Regional Exposures
The American College of Obstetricians and Gynecologists recognizes that climate change is an urgent women’s health concern as well as a major public health challenge 45. Along with air pollution, extreme heat and extreme cold may be associated with adverse fetal outcomes, including preterm birth 33 34 35 36 37 38 and low birth weight 33 40 41 42 46.
Clinical Assessment and Counseling
Environmental Health History
Obstetrician–gynecologists and other obstetric care clinicians should consider including questions about environmental exposures in the patient history during prepregnancy visits and prenatal care Table 2. An environmental health history is the key first step in identifying specific types of potentially harmful exposures to the pregnant individual and fetus to tailor appropriate exposure reduction strategies. Typical elements of an environmental health history include assessment for exposures from the workplace, home, or recreational activities Table 2. For example, prepregnancy and prenatal counseling can include an assessment of lead exposure in these domains. Screening questions for lead exposure are further reviewed in ACOG Committee Opinion No. 533, “Lead Screening During Pregnancy and Lactation” 47.
After an environmental health history and assessment is completed, obstetrician–gynecologists and other obstetric care clinicians are encouraged to provide information regarding reducing exposure to toxic agents at home, in the community, and at work, being mindful of economic and other costs that reduction may entail. If an exposure is identified, patients can be educated regarding avoiding or reducing exposure to toxic agents where possible and, when necessary, referred to occupational medicine programs or to the United States Pediatric Environmental Health Specialty Units 48.
Counseling About Environmental Exposures
Obstetric care clinicians do not need to be experts in environmental health science to provide useful information to patients and to refer patients to appropriate specialists, if needed, when a hazardous exposure is identified. Existing clinical experience and expertise in communicating risks of treatment are largely transferable to environmental health. Many of the opportunities for counseling on environmental exposures occur during routine elements of prenatal and prepregnancy care when discussing topics such as food and water-related exposures, personal care products, and lifestyle modification Table 2.
The Precautionary Principle states that in cases of serious or irreversible threats to the health of humans or ecosystems, acknowledged scientific uncertainty should not be used to postpone preventive measures 22. This principle can help guide clinical counseling about reduction of exposures that are known or considered to be potentially toxic until more evidence is gathered regarding the clinical efficacy of specific interventions. Clinician contact time with a patient does not need to be the primary point of intervention. Information and resources about environmental hazards can be successfully incorporated into a childbirth class curriculum or provided to patients in the form of written materials to help parents identify opportunities to reduce exposure for themselves and their children 49.
Workplace and Occupational Exposures
Employment sectors at particular risk of potentially hazardous exposures during pregnancy include agriculture (pesticides), manufacturing (organic solvents and heavy metals), dry cleaning (solvents), custodial and cleaning services (organic solvents), beauty salons (solvents and phthalates), and health care (biologics and radiation) 48. In some cases, cleaning supplies containing chemicals can be replaced with less toxic options. By Occupational Safety and Health Administration (OSHA) standards, employers are required to ensure that exposures to workplace hazards do not harm workers’ health 51. Additionally, there are rights that employees have to a safe and healthy workplace, and obstetrician–gynecologists and other obstetric care clinicians can provide information and resources to their patients and partners that might help them better understand these rights. 51 52.
Patients should be advised that some large fish, such as shark, swordfish, king mackerel, and tilefish, are known to contain high levels of methylmercury, which is teratogenic 53. Individuals in the prepregnancy period and those who are pregnant or lactating should avoid these fish and be encouraged to eat a variety of other types of fish Box 1. Pregnant and lactating individuals also should check local advisories regarding the safety of fish caught in local lakes, rivers, and coastal areas 53.
Food preparation and storage can play a role in toxic exposure reduction. Patients can be advised to thoroughly wash raw produce to reduce bacterial contamination, even if it will be peeled or cut; however, it is unclear whether this will reduce all toxic chemical exposures (eg, perchlorate or pre- and polyfluoroalkyl substances [PFAS]) 54 55. Although there is limited evidence available, heating foods in plastic containers, including polystyrene, may increase exposure to plastic resins that may have endocrine-disrupting effects. Patients can be counseled that preparing and storing foods in glass or nonplastic containers may reduce their risk of exposure to these plastic resins. In addition, because consuming fast food has been associated with exposure to endocrine disruptors such as phthalates, recommendations to prepare meals at home or avoid fast food have the potential to reduce these exposures 56 57.
Individuals can take actions to reduce their exposures to toxic chemicals 58 59 60. For example, research has shown that when children’s diets change from conventional to organic, the levels of pesticides in their bodies decrease 59 60. Likewise, avoiding dietary sources of bisphenol A (BPA) (eg, some canned food) can reduce measured levels of the chemical in children and adult family members, and short-term changes in dietary behavior may substantially decrease exposure to phthalates 58 59. Although these data underscore the importance of selecting foods without pesticides, BPA, and phthalates whenever possible, it should be acknowledged that not all individuals will have ready physical or financial access to these food options. In addition, future research on the efficacy of implementing modifiable interventions to reduce these environmental exposures and effects is needed.
Personal Care Products
Personal care and cosmetic products may contain unrecognized toxins. Products marketed to individuals of color (particularly skin lighteners and hair straighteners) have been found to contain mixtures of endocrine-disrupting chemicals (eg, parabens and phthalates), but these chemicals often are not listed on the labels 62 63. Although there are reported associations between exposure to endocrine-disrupting chemicals and adverse obstetric outcomes, more research is needed to understand if there is causality and, if so, at what levels of exposure or use of a specific product. Of note, although studies are limited, there is no evidence suggesting that the use of hair dye in pregnancy is associated with adverse obstetric outcomes.
Selecting products labeled “fragrance-free” rather than “unscented” may help reduce exposure to endocrine-disrupting chemicals because unscented products may contain multiple scents, still bound by phthalates, that are mixed to cancel each other out. Patients can be counseled that selecting cosmetic and personal care products without phthalates, parabens, oxybenzone, and triclosan may lower their exposure 64.
Regional Environmental Exposures
It is important for obstetrician–gynecologists and other obstetric care clinicians to become knowledgeable about toxic environmental exposures that are endemic to their specific geographic areas, such as local water safety advisories (eg, lead-contaminated water), local air quality levels, and patients’ proximity to power plants and fracking sites. Clinical counseling can include recommending avoidance of outdoor exercise during peak times for air pollution and relaying key messages from local safety advisories. Obstetrician–gynecologists and other obstetric care providers in communities near coal power plants or fracking sites can stay apprised of potential adverse obstetric outcomes associated with proximity to these sites 43 44.
The Role of Obstetric Care Clinicians in Environmental Health Beyond the Clinical Setting
Reporting identified hazards is critical to prevention of further exposures and poor obstetric outcomes. Local and state health agencies and the Association of Occupational and Environmental Clinics serve as resources for reporting occupational and environmental illnesses.
More research is needed to confirm and better understand the mechanisms between specific environmental health exposures and adverse obstetric outcomes and to guide clinical recommendations. The American College of Obstetricians and Gynecologists fully supports rigorous scientific investigation into links between environmental hazards and adverse reproductive and developmental health outcomes. Systematic review methods based on best practices in clinical medicine (eg, Cochrane and GRADE) have been developed and used for evaluating environmental health science, and their application should be expanded to improve the evidentiary basis for decision making 65. Environmental health surveillance, including measuring and tracking chemicals in individuals and the environment, is critical to this effort 32.
Obstetrician–gynecologists and other obstetric care clinicians can be effective in reducing prenatal exposure by recognizing and responding to environmental exposures and counseling patients appropriately 66 67. Action at the individual level can reduce exposure to some toxic chemicals 58 59 60, but individuals alone cannot reduce many exposures. Evidence-based recommendations for preventing harmful environmental exposure ultimately must also include policy change 68 69. Policies to limit the manufacturing and use of harmful chemicals are effective in reducing exposures 71 72 73. Accordingly, many medical associations have taken steps in that direction. The American College of Obstetricians and Gynecologists and the American Society for Reproductive Medicine have joined the American Academy of Pediatrics and numerous other health professional organizations in calling for timely action to identify and reduce exposure to toxic environmental agents while addressing the consequences of such exposure 2 74 75.
Environmental health is an important consideration for healthy individuals, pregnancies, fetuses, and infants. Obstetrician–gynecologists can help to optimize the long-term and short-term health of the pregnant individual and the fetus by assessing for risks of toxic exposure and counseling about exposure reduction. Obstetrician–gynecologists and other obstetric care clinicians do not need be experts in environmental health science to provide useful information to patients and to refer patients to appropriate specialists, if needed, when a hazardous exposure is identified. It may be beneficial to integrate environmental health into obstetrics and gynecology training and practice. Advocating for policies that will reduce harmful exposures and protect the health of pregnant individuals and their children is encouraged.