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Study Examines Associations Between Antibiotic Use During Pregnancy, Birth Defects

CHICAGO -- November 2, 2009 -- Penicillin and several other antibacterial medications commonly taken by pregnant women do not appear to be associated with many birth defects, according to a study published in the November issue of Archives of Pediatrics & Adolescent Medicine.

However, other antibiotics, such as sulfonamides and nitrofurantoins, may be associated with several severe birth defects and require additional scrutiny.

Although some classes of antibiotics appear to have been used safely during pregnancy, no large-scale studies have examined safety or risks involved with many classes of antibacterial medications.

Krista S. Crider, PhD, Centers for Disease Control and Prevention, Atlanta, Georgia, and colleagues analysed data from 13,155 women whose pregnancies were affected by 1 of more than 30 birth defects (cases). The information was collected by surveillance programs in 10 states as part of the National Birth Defects Prevention Study.

The researchers compared antibacterial use before and during pregnancy between these women and 4,941 randomly selected control women who lived in the same geographical regions but whose babies did not have birth defects.

Antibacterial use among all women increased during pregnancy, peaking during the third month. A total of 3,863 mothers of children with birth defects (29.4%) and 1,467 control mothers (29.7%) used antibacterials sometime between 3 months before pregnancy and the end of pregnancy.

"Reassuringly, penicillins, erythromycins and cephalosporins, although used commonly by pregnant women, were not associated with many birth defects," the authors wrote. Two defects were associated with erythromycins (used by 1.5% of the mothers whose children had birth defects and 1.6% of controls); 1 with penicillins (used by 5.5% of case mothers and 5.9% of controls); 1 with cephalosporins (used by 1% of both cases and controls); and 1 with quinolones (used by 0.3% of both cases and controls).

Two medications -- sulfonamides and nitrofurantoins (each used by 1.1% of cases and 0.9% of controls) -- were associated with several birth defects, suggesting that additional study is needed before they can be safely prescribed to pregnant women.

"Determining the causes of birth defects is problematic," the authors wrote. "A single defect can have multiple causes, or multiple seemingly unrelated defects may have a common cause. This study could not determine the safety of drugs during pregnancy, but the lack of widespread increased risk associated with many classes of antibacterials used during pregnancy should be reassuring."

SOURCE: Archives of Pediatrics & Adolescent Medicine

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