MONDAY, Nov. 2 (HealthDay News) -- Taking antibiotics during pregnancy does not raise the risk for most birth defects, though there are some exceptions, new research has found.
Penicillin, which is the most commonly used antibiotic during pregnancy, as well as erythromycin, cephalosporins and quinolones, other widely prescribed antibiotics, were not associated with increased risk for about 30 different birth defects.
However, the study found that two types of antibiotics were linked with a higher risk for several birth defects: nitrofurantoins and sulfonamides, sometimes called "sulfa drugs," which are prescribed for urinary tract and other infections.
Women whose children had anencephaly, a fatal malformation of the skull and brain, were three times more likely to have taken sulfonamides, the study found. Sulfonamides were also tied to an increased risk for such heart defects as hypoplastic left heart syndrome and coarctation of the aorta, choanal atresia (a blockage of the nasal passage), transverse limb deficiency and diaphragmatic hernia, an abnormal opening in the diaphragm that results in severe breathing difficulties.
Nitrofurantoins were also associated with multiple birth defects, including anophthalmia and microphthalmos (eye defects) and several congenital heart defects. Mothers whose children were born with a cleft lip or cleft palate were twice as likely to have taken nitrofurantoins, the study found.
But pregnant women should not be overly worried if they need an antibiotic to treat an infection during pregnancy, stressed the study's lead author, 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.
"The most important message is that most commonly used antibiotics do not seem to be associated with the birth defects we studied," Crider said.
The findings are published in the November issue of Archives of Pediatrics & Adolescent Medicine.
Crider and her colleagues analyzed data on more than 13,000 women whose babies had one of more than 30 birth defects, including cleft palate, heart or limb defects and anencephaly. They compared the women's rates of antibiotic usage, from the month leading up to pregnancy through the end of the first trimester, with that of almost 5,000 women whose children did not have a birth defect. The data was culled from the National Birth Defects Prevention Study, which began in 1997 and includes about 30,000 women from 10 states.
Information on the impact of many prescription drugs on developing fetuses is sorely lacking, Crider pointed out. Much of that stems from the fact that ethical considerations preclude conducting drugs trials in pregnant women, she said.
Though many antibiotics have been used safely for decades, resistant strains of bacteria are forcing doctors to use a wider array of antibiotics. For some, little data exist.
The researchers found that about 30 percent of women took an antibiotic between the three months prior to conception and the end of the pregnancy.
Even antibiotics that generally were safe were found to be associated with a few specific birth defects. Women whose babies were born with a certain type of limb malformation were three times more likely to have taken penicillin. Erythromycin, cephalosporins and quinolones were also associated with an increased risk for one or two specific birth defects.