Drugs in pregnancy

Pregnancy categories

Categorization of drug safety in pregnancy differs by country. Until 2014, the U.S. Code of Federal Regulations required certain drugs and biological products to be labelled with a pregnancy category (A, B, C, D, or X), enforced by the FDA, based on study results. In 2014, the FDA replaced this with the Pregnancy and Lactation Labeling Rule (PLLR), which mandates product labels include specific safety and effectiveness information for pregnant and lactating women, removing the requirement for pregnancy categories on prescription drug labels. Australia's system considers birth defects, effects around birth, and later-life problems, placing drugs into categories based on the severity of consequences when the drug crosses the placenta.

Medications

Medication use during pregnancy requires careful evaluation of risks and benefits. Healthcare professionals can help weigh these factors, as some medications are necessary for maternal and fetal health, while others may pose risks that are sometimes outweighed by benefits. Short-term use of acetaminophen as directed is one of the few recommended pain and fever treatments in pregnancy, with no established link to birth defects; however, maternal overdose can cause fetal liver toxicity.

Ibuprofen and naproxen have not been extensively studied in pregnancy; recent studies show no increased risk of spontaneous abortion in the first six weeks, but all NSAIDs are associated with structural cardiac defects when used early in pregnancy. Use in the third trimester significantly raises the risk of premature closure of the ductus arteriosus with primary pulmonary hypertension in the newborn. Pregnant women are advised to avoid these medications or use them sparingly per physician advice.

Aspirin is not recommended for pain relief during pregnancy; while it does not increase early spontaneous abortion risk, use during organogenesis and the third trimester can elevate risks of intrauterine growth retardation and maternal hemorrhage. Low-dose aspirin is used to prevent preeclampsia and fetal growth restriction in patients with prior risk factors such as previous preeclampsia, multiple pregnancies, hypertension, and diabetes.

Dietary supplements

Dietary supplements like folic acid and iron are important for a healthy pregnancy, but some can cause harm. Pregnant women should discuss all supplements with their healthcare professional to determine safe dosages. Dietary supplements are classified as foods rather than medications and are not regulated for safety and efficacy by the FDA. Many countries, including the USA, Canada, Chile, and Costa Rica, have fortified foods with folic acid, resulting in reduced neural tube defect (NTD) incidence.

The CDC recommends 400 μg of folic acid daily for all women of childbearing age, even if not planning pregnancy. Women who have had an NTD-affected pregnancy and plan to become pregnant again should take 4000 μg daily for one month before and the first three months of pregnancy. In that study, 6 out of 593 infants (1%) in folic acid groups had NTD recurrence, versus 21 out of 602 (3.5%) in groups without folic acid; no significant benefit was found from other vitamins.

Iron deficiency is common in pregnancy, especially in the third trimester, due to increased demand for the placenta, fetal development, and infant iron stores. Low iron can cause fatigue, reduced work capacity, cardiovascular stress, lower infection resistance, and iron deficiency anemia, which raises risks of premature delivery, low birth weight, and perinatal mortality.

Illicit and recreational drugs

Substance abuse, as defined by the World Health Organization, involves damaging or risky consumption of psychoactive substances including alcohol and illegal drugs. When pregnant women use psychotropic substances, whether prescribed or not, adverse effects on the developing fetus can include birth defects, delayed development, and intrauterine growth restriction. It also raises the likelihood of pregnancy complications such as spontaneous miscarriage, preterm birth, and maternal issues like postpartum bleeding and placental abruption.

Alcohol should not be consumed during pregnancy, as even small amounts are not known to be safe. Alcohol passes easily from the mother's bloodstream through the placenta to the fetus, where it remains longer due to the fetus's smaller size and immature liver, increasing the risk of harm. The severity of effects depends on the amount and frequency of alcohol consumed, maternal weight, age, alcohol metabolism, and stage of pregnancy. Heavy and binge drinking are closely linked to fetal alcohol spectrum disorders (FASDs), with fetal alcohol syndrome (FAS) being the most severe form.

FAS is characterized by slower physical growth, distinct facial abnormalities (smooth philtrum, thin vermilion, short palpebral fissures), neurological deficits, and smaller head circumference. Other FASD problems include delayed motor skills, hearing or vision issues, learning disabilities, behavior problems, and poor social skills. Affected individuals are more likely to have trouble in school, legal problems, engage in high-risk behaviors, and develop substance use disorders. Alcohol consumption is also a risk factor for miscarriage.