Two Antibiotics Linked to Birth Defects
Most antibiotics used during pregnancy are safe, but researchers have found a link between two commonly prescribed drugs and birth defects.
The study, part of the National Birth Defects Prevention Study and published in the November issue of Archives of Pediatrics and Adolescent Medicine, is the first analysis of antibiotic use in pregnancy. Researchers analyzed data from 13,155 mothers in 10 states whose infants had birth defects and compared them to mothers in the same region who had healthy babies.
It found that mothers of babies with birth defects were more likely to report taking two types of antibiotics used to treat urinary tract infections during the first three months of pregnancy – sulfa drugs such as Bactrim and Septra, and nitrofurantoins, a urinary germicide that includes the brand names Furadantin, Macrobid, and Macrodantin.
Penicillin, the most commonly prescribed antibiotic in early pregnancy, was found to be safe, but was linked to a slightly increased risk for limb defects. Also found to be safe were cephalosporins and quinolones.
Lead author of the study, Krista Crider, a geneticist with the Centers for Disease Control and Prevention said that this was the first study to find an association with the drugs and birth defects and additional studies are need to confirm the findings.
Sulfa drugs are the oldest antibiotics and some animal studies have found harm during pregnancy. The study found this group of drugs to be associated with six birth defects, more than any other class of antibiotic. Defects linked to sulfa drugs included rare brain and heart defects and shortened limbs. Anencephaly, a fatal brain and skull malformation linked to sulfa drugs, affects about 1 in 10,000 births in the United States per March of Dimes data.
Doctors have previously viewed nitrofurantoins as safe to treat urinary tract infections during pregnancy. The four defects most commonly linked with these medications included hypoplastic left heart syndrome, atrial septal defect, eye defects, and cleft lip and palate. Cleft palate occurs in about 20 births out of 10,000 and was twice as likely to occur with women who had taken the nitrofurantoins.
It is unclear whether the birth defects were caused by the drugs or by the infections being treated. Bacterial infections themselves can cause problems for the fetus if left untreated, including preterm birth, low birth weight and blindness, so pregnant women shouldn't avoid antibiotics entirely. Instead, women should discuss antibiotics choices with their doctors.
Additional Sources Include: The Centers for Disease Control and Prevention and the March of Dimes