CDC study finds two antibiotics linked to birth defects

Prescription bottles (photo by Penywise)

Researchers from the Centers for Disease Control and Prevention (CDC) have linked the prenatal use of two types of antibiotics to an increased risk of birth defects. The antibiotics in question are nitrofurantoins and sulfonamides, also known as sulfa drugs. These antibiotics are used to treat urinary tract infections, bronchitis, pneumonia, and other types of bacterial infections.

The researchers analyzed the antibiotic usage of 13,155 women whose babies had one of more than 30 birth defects and 4941 women whose babies did not have these birth defects. All the women had used antibiotics during the period of one month before pregnancy and the end of the first trimester.

The results showed women who took sulfonamides had a greater risk of having babies with anencephaly (a fatal defect involving the brain and skull), hypoplastic left heart syndrome (a deformation of the heart), coarctation of the aorta (narrowing of the aorta), choanal atresia (narrowing or blockage of the nasal airways), transverse limb deficiency (malformation of the limbs), and diaphragmatic hernia (an abnormal opening in the diaphragm). Nitrofurantoins increased the risk of anophthalmia and microphthalmos (malformation of the eyes), hypoplastic left heart syndrome, atrial septal defects (an opening in the wall between the left and right sides of the heart) and cleft lip with cleft palate.

The abstract of the study states, “Reassuringly, penicillins, erythromycins, and cephalosporins, although used commonly by pregnant women, were not associated with many birth defects.” The risk from these antibiotics was considered low when compared to overall usage of the drugs during pregnancy.

Dr. Jennifer Wu, an obstetrician-gynecologist at Lenox Hill Hospital in New York City, warns women against avoiding all antibiotics during pregnancy.

"Untreated infections during pregnancy can lead to severe consequences, such as maternal sepsis [blood infection] and preterm labor," said Dr. Wu.

Dr. Wu continued by saying the study "supports the evidence that antibiotics are safe for pregnant women.”

"The most important message is that most commonly used antibiotics do not seem to be associated with the birth defects we studied," said Krista Crider, a geneticist with the National Center on Birth Defects and Developmental Disabilities, part of the U.S. Centers for Disease Control and Prevention and lead author of the study.

Crider warns women should avoid taking nitrofurantoins and sulfonamides during their pregnancy and speak to their doctors about other treatment options.

Common brand names for nitrofurantoin antibiotics are Furadantin, Macrobid, Macrodantin. Common brand names for sulfonamides include Bactrim and Septra.

The study was published in the November issue of Archives of Pediatrics & Adolescent Medicine.

For more info: For more information on the birth defects mentioned in this article, please visit the website of the National Center on Birth Defects and Developmental Disabilities.

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