Antibiotic use in pregnancy

Infections are common during pregnancy, and a significant number of pregnant women are exposed to antibiotics. Urinary tract infections such as bacteriuria, cystitis, and pyelonephritis are among the most common, occurring in 2% to 7% of all pregnant women.(32) Other frequently encountered infections include community acquired pneumonia, chorioamnionitis, and sexually transmitted diseases. Ln addition, metritis and mastitis may complicate the postpartum period. Virtually all antibiotics cross the placenta and thus have the potential to affect the fetus adversely. Most are excreted into breast milk and may affect the neonate as well. There are no large scientific studies of the safety of antibiotics in pregnancy. Many agents, however, such as the penicillins and erythromycin, have been used for many years in pregnancy (out of necessity) without apparent adverse fetal effects. Timing the treatment of an infection during pregnancy depends somewhat on its nature and severity. A serious infection such as acute pyelonephritis should be treated as soon as the diagnosis is made. On the other hand, treatment of vaginitis might be delayed until after the first trimester. When giving an antibiotic to a pregnant woman, it is important to be cognizant of the physiologic changes that may alter its pharmacodynamics. The marked increases in blood volume and creatinine clearance that occur in pregnancy typically lead to lower serum concentrations. For example, a given dose of ampicillin or gentamicin will result in lower serum levels in pregnant versus nonpregnant women.(15, 31, 41, 56)