Many people know that developing fetuses are especially vulnerable to toxic chemicals — this is why during pregnancy doctors advise you not to eat fish high in mercury as it affects the fetus’ rapidly growing brain. But ask anyone who has been pregnant, and they’ll tell you their bodies also underwent radical changes. To better understand what the science says about pregnancy and health, we conducted a comprehensive review on chemical exposures and adverse health outcomes, including pregnancy-induced hypertensive disorders, gestational diabetes, and breast cancer. We found that it’s not just about the fetus, pregnancy can be a risk factor for major lifelong health vulnerabilities.
Major changes to basic body systems
During pregnancy, a number of biological changes occur to accommodate the developing and growing fetus, such as changes to blood flow, how the body processes sugar, and how the breasts enlarge and prepare for milk production. These changes can heighten one’s vulnerability to a wide range of stressors, including chemical stressors and can be taxing on the pregnant body, especially if a pregnant person is already at high risk for certain conditions like diabetes or hypertension, which can increase risk for health complications later in life (see Figure 1).
Blood flow changes and pregnancy-induced hypertensive disorders
The placenta is a powerful new organ that forms from the outer layer of the embryo, protecting it after fertilization. The placenta invades and remodels uterine blood vessels to redirect blood flow towards what’s known as the “maternal-fetal interface”, where it then filters toxic compounds and provides nutrients for fetal growth. Blood supply increases to ensure enough oxygen/nutrients reach both pregnant person and fetus, requiring blood vessels to expand and blood pressure to decrease (initially and then increase later). While these changes are critical to fetal health, they leave pregnant people susceptible to chemical exposures that contribute to pregnancy-related health complications like gestational hypertension, preeclampsia (a dangerous systemic disorder for which delivery–often too early–is the only known cure), and other hypertensive disorders. For example, lead and other heavy metals can induce hypertension and preeclampsia during pregnancy.
Changes to metabolism and gestational diabetes
During pregnancy, the metabolism shifts to breakdown fats in order to preserve glucose (sugar) for the fetus, resulting in prediabetic high blood sugar and insulin levels. While the body requires a 200% increase on average in the production of insulin to counter high blood glucose levels, gestational diabetes can develop when pregnant people are unable to produce enough insulin to meet the new demand. This is even more difficult for people who already struggle with keeping their insulin or glucose levels in check. Chemicals like PBDEs and PFAS which promote insulin resistance, high blood sugar, and/or problems breaking down fats or sugars may contribute to the risk of gestational diabetes.
Preparing for milk production and breast cancer
Pregnancy is a transformative stage of breast development, displacing the fatty tissue of the “immature” adult breast with a dense network of milk-producing buds to make breast milk after delivery (Figure 1). These changes to breast tissue are largely driven by hormones like estrogen, making them vulnerable to endocrine disrupting compounds (EDCs) like BPA, which can interfere with the body’s natural estrogen activity.
Influence of Endocrine Disrupting Chemicals
Because the endocrine system is responsible for coordinating major biological changes during pregnancy, EDCs can also contribute to preeclampsia, hypertension, and diabetes during pregnancy. As pregnancy moves a person closer to disease thresholds, increasing health risks, it can also heighten sensitivity to chemical exposures that contribute to these diseases, creating a vicious cycle. This combination of biological and environmental exposures is referred to as the exposome. Therefore, pregnancy should be considered a vulnerable period for health, just like puberty, with lifelong health implications for the pregnant person (Figure 2).
Our review of the science showed that pregnancy should be treated as a critical stage for health and that chemical exposures during this time should be minimized to protect the health of both pregnant person and baby. Researchers should consider more than just fetal health outcomes, healthcare providers should educate patients on the impact of pregnancy for health across the life span, and policy makers should pass regulations to protect pregnant people. After all, while I agree with Johnny (in one of my favorite 80s movies of all time) that nobody puts baby in a corner–we need to acknowledge the impact of pregnancy on health too!
Note: While our study is about pregnant women, it is important to acknowledge that not all who are pregnant identify as women (and not all who are pregnant are parents).
My co-authors on this study were Anna Smith, Aolin Wang, Elizabeth Hom, Monika Izano, Hongtai Huang, Amy Padula, and Tracey Woodruff.