Prescription drugs may impact the fetus through several mechanisms. They can directly damage the fetus by crossing the placenta, alter the functioning capacity of the placenta so that the fetus’ oxygen and nutrient supply is reduced, induce forceful uterine contractions which can injure the fetus, or indirectly harm the fetus by affecting the internal environment of the mother.
The CDC reports that prescription and over-the-counter medication use during pregnancy has increased by 70% over the past 3 decades. Less than 10% of all medications approved by the FDA since 1980 have been studied well enough to assess their risk for birth complications, and, pregnant women are not included in drug safety trials because of liability concerns. Furthermore, only 2 out of the 54 most commonly used prescription and over-the-counter medications have enough data available to determine how they can impact a pregnancy.
There have been many studies conducted over the years that have examined how specific prescription medications taken during pregnancy may affect the health outcomes of children. Prescription medications that have been associated with an increased risk of birth defects or other childhood health complications include antidepressants, hypertension medications, mycophenolate mofetil (for treating autoimmune diseases), anti-epileptic medications, clomiphene citrate (to treat infertility), sulfonamide and nitrofurantoin (to treat infections), and opioids.
A study from JAMA found that taking antidepressants during the second or third trimester of a pregnancy increased the risk of having a child with autism by 87%, and that selective serotonin reuptake inhibitors (SSRIs) taken at any point during the pregnancy were associated with an even greater risk of having a child with autism. These researchers note that SSRIs can cross the placenta and impact the development of the fetus. There is also evidence that autistic individuals have high levels of serotonin in their blood platelets and that their brains synthesize serotonin atypically. Another study found that the asthma drugs- beta-2 adrenergic receptor (B2AR) agonists taken 90 days before pregnancy or during pregnancy increase the risk of having a child with autism.
Antibiotic use both medically and agriculturally is a major health concern. The CDC states that approximately 29% of antibiotic prescriptions in the United States in 2015 for children 0-19 years of age were unnecessary. Excessive antibiotic use puts the recipients at risk for adverse reactions or infection and can result in long-term alterations to the recipient’s microbiome. A healthy microbiome is essential for regular metabolism, vitamin production, and homeostasis regulation. Furthermore, babies born vaginally receive their mother’s microbiome as they pass through the birth canal. A mother’s microbiome will be altered when she takes antibiotics before or during pregnancy and can pass this altered microbiome to her child during childbirth.
One study has found that the antibiotics amoxicillin and clavulanate specifically may be contributing to the rise of autism. According to the study, after the introduction of these antibiotics in 1987, the state of California reported an increase in the rate of autism by 273% in a single year. The study proposes that the production of these antibiotics may yield high levels of urea/ammonia in the child. Another study found evidence that taking antibiotics during pregnancy can induce neurodevelopmental changes in the fetus in utero.
Agricultural antibiotics account for approximately 80% of all antibiotic usage in the United States. Animals are treated with low dose antibiotics to prevent the spread of disease and to promote growth. These antibiotics are transferred to humans through the meat we consume, as well as through the crops that were fertilized with the animals’ waste. Consumption of food contaminated with antibiotics can induce the same health consequences as prescribed antibiotics.
Specific over-the-counter medications have also been found to impact the health of the fetus. The commonly used drugs Ibuprofen, ketoprofen, and naproxen are some examples. Acetaminophen has long been considered relatively safe to take during pregnancy, however, acetaminophen use during pregnancy was associated with a 50% increase in the risk of having a child with autism and hyperkinetic disorder. Also, a longer duration of acetaminophen use resulted in a 2-fold increase in the risk of having a child with autism.
Since pregnant women are excluded from trials, some drugs are tested on pregnant animals instead. However, animal studies should not be considered reliable in determining the safety of a drug, as exemplified by the thalidomide incident in the 1950s. Thalidomide was a drug that was intended to treat morning sickness in pregnant women. Although it did not have any adverse effects on the pregnancy outcomes of rats during animal studies, it was found to cause severe and often fatal birth defects in infants and is now recognized as one of the most hazardous known human teratogens.
Although many studies have found associations between medications taken during pregnancy and poor childhood health outcomes, researchers state in their discussions that the exact mechanism through which the drug impacts the fetus remains uncertain.