Four in five pregnant women in the United States have a prescription drug dispensed, and nearly half are given drugs that may be harmful to the fetus, a study of Medicaid records has found. In the study Kristin Palmsten, of the University of California, SanDiego and colleagues reviewed outpatient pharmacy records from 2000 to 2007 on 1 106 757 pregnant women who were covered by Medicaid, the health insurance plan for low income earners and disabled people. They found that 82.5% of the cohort had received one or more prescription drugs during pregnancy. The most commonly dispensed drug classes were antibacterials, dispensed to 49.7% of the women; analgesics and antipyretics (29.6%); skin and mucous membrane anti-infectives (28.7%); urinary anti-infectives (21.7%); and first generation antihistamines (18.6%). The most commonly dispensed drugs were nitrofurantoin, metronidazole, amoxicillin, azithromycin, and promethazine. Excluding fertility treatments, 42% of the women were given a drug that had been designated by the US Food and Drug Administration as potentially harmful to fetuses—receiving either a D classification, indicating positive evidence of risk but also of benefits that may warrant use; or an X classification, meaning that the drug is contraindicated in pregnancy. The most commonly dispensed category D drugs were codeine, dispensed to 11.9%, and hydrocodone, dispensed to 10.2%. The most commonly dispensed category X drugs were hormonal contraceptives, which were dispensed to 4.9% of the women during their pregnancy. The other four most commonly dispensed category X drugs were temazepam, atorvastatin, simvastatin, and warfarin. (As of 30 June 2015 the FDA’s letter classification system has been replaced by a narrative risk summary based on available data.) The researchers noted that, of the 20most commonly dispensed drugs, nine were rated by the Teratogen Information System as having limited to fair data quality and quantity to inform human teratogenic risk assessments, and the other 11 received fair to good ratings. “Lack of unambiguous safety information may lead to the use of medications with potential to cause adverse pregnancy outcomes, whereas beneficial medications may be avoided,” the researchers concluded.