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Potentially Unsafe Antibiotics Prescribed to Pregnant Women with Urinary Tract Infections

Urinary Tract Infections (UTI) are a common condition during pregnancy. As a woman’s uterus expands to accommodate a growing baby, the extra pressure and weight can interfere with the ability to fully empty the bladder, causing bacteria to multiply and lead to infection. UTIs can have serious implications for a fetus, including pre-term labor. As part of routine prenatal care, obstetricians are advised to obtain a urine culture at every prenatal appointment to ensure that bacteria indicative of a UTI is not present in a pregnant mother’s urine.

Last month the CDC issued a ‘Morbidity and Mortality Weekly Report” about the high number of prescriptions filled by pregnant women for sulfonamides and nitrofurantoin, two common types of drugs to treat UTIs. The report advises health care providers that treat pregnant or potentially pregnant women to use formulations of these two types of drugs with caution due to a 2009 study that indicated a relationship between birth defects and their use during the first trimester.

More Than a Third of Pregnant Women with UTI Filled Sulfonamide or Nitrofurantoin Prescription  
After a CDC review of insurance claims from 2014, researchers found that nitrofurantoin and trimethoprim-sulfamethoxazole were frequently prescribed to pregnant women in their first trimester. Their research found that 34.7% of women with UTIs in their first trimester filled a prescription for nitrofurantoin in 2014. That same year, 7.6% filled a trimethoprim-sulfametoxazole prescription. This means that 4 in 10 women, or 42.3%, filled a prescription for one of these potentially harmful drugs.

Guidelines published in 2011 from the Infectious Diseases Society of America advise the two medications as drugs of choice for treating UTIs in NON pregnant women. A September 2017 opinion from the American College of Obstetricians and Gynecologists (ACOG) said that studies regarding a link to birth defects and use of sulfonamides or nitrofurantoin during early pregnancy as “mixed,” but recommends that physicians treating pregnant women in their first trimester should first consider other appropriate antibiotics before using the 2 potentially-harmful types of drugs. ACOG’s conclusion is that the drugs are “still considered approrpiate when no other suitable alternative antibiotics are available.”

It seems surprising that 42% of women with UTIs in early pregnancy were not able to take alternative antibiotics that could treat a urinary tract infection. Other traditionally suitable drugs used to treat UTIs include cephalosporins, erythromycin, and penicillins. Furthermore, the intent of the CDC’s weekly report regarding the frequency of 1st trimester use of sulfonamides and nitrofurantoin was to caution not only providers knowingly treating pregnant women, but also for any provider who treats a woman of childbearing years for a UTI.

While studies have not definitively proven that these drug types cause birth defects, all studies involving pregnant women are limited by an unwritten code of ethics which discourages researchers from exposing fetuses to harm. While a pregnant woman could legally consent to a study or trial, a fetus cannot. According to ACOG, one of the main limitations of studies involving sulfonamides and nitrofurantoin is that they are relying on postpartum women to recall whether or not they took one of these types of drugs while pregnant.

While ACOG has decided that the connection between sulfonamides and nitrofurantoin hasn’t been fully proven, when it comes to the health of an unborn child, it seems wise to always ask your healthcare provider about the safety of any medication you’re taking while pregnant.