Most common maternal infections (eg, UTIs, skin and respiratory tract infections) are usually not serious problems during pregnancy, although some genital infections (bacterial vaginosis and genital herpes) affect labor or choice of delivery method. Thus, the main issue is usually use and safety of antimicrobial drugs. However, certain maternal infections can damage the fetus (for congenital cytomegalovirus or herpes simplex virus infection, rubella, toxoplasmosis, hepatitis, or syphilis, see Infections in Neonates; for HIV infection, see Human Immunodeficiency Virus (HIV) Infection in Infants and Children).

Listeriosis is more common during pregnancy. Listeriosis increases risk of spontaneous abortion, premature labor, and stillbirth. Neonatal transmission is possible.

Bacterial vaginosis and possibly genital chlamydial infection predispose to premature rupture of the membranes and preterm labor. Tests for these infections are done during routine prenatal evaluations or if symptoms develop.

Genital herpes can be transmitted to the neonate during delivery. Risk is high enough that cesarean delivery is preferred in the following situations:

• When women have visible herpetic lesions
• When women who have a known history of infection develop prodromal symptoms before labor
• When herpes infection first occurs during the late 3rd trimester (when the virus is likely to be excreted from the cervix at delivery)

If visible lesions or prodrome is absent, even in women with recurrent infections, risk is low, and vaginal delivery is possible. If women are asymptomatic, serial antepartum cultures do not help identify those at risk of transmission. If women have recurrent herpes infections during pregnancy but no other risk factors for transmission, labor can sometimes be induced so that delivery occurs between recurrences. When delivery is vaginal, cervical and neonatal herpesvirus cultures are done. AcyclovirSome Trade Names
ZOVIRAX
Click for Drug Monograph
(oral and topical) appears to be safe during pregnancy.

Antibacterials: Not giving antibacterials to pregnant patients without strong evidence of a bacterial infection is particularly important. Generally, penicillins, cephalosporins, and macrolides are considered safe. Use of any antibacterial during pregnancy should be based on whether benefits outweigh risk, which varies by trimester (see Table 2: Drugs in Pregnancy: Some Drugs With Adverse Effects During Pregnancy for specific adverse effects). Severity of the infection and other options for treatment are also considered.

Aminoglycosides may be used during pregnancy to treat pyelonephritis and chorioamnionitis, but treatment should be carefully monitored to avoid maternal or fetal damage.

Chloramphenicol, even in large doses, does not harm the fetus; however, neonates cannot adequately metabolize chloramphenicolSome Trade Names
CHLOROMYCETIN
Click for Drug Monograph
, and the resulting high blood levels may lead to circulatory collapse (gray baby syndrome). ChloramphenicolSome Trade Names
CHLOROMYCETIN
Click for Drug Monograph
is rarely used in the US.

Metronidazole use during the 1st trimester is controversial, but the drug is routinely used to treat bacterial vaginosis and trichomoniasis during the 2nd and 3rd trimesters.

Fluoroquinolones are not used during pregnancy; they tend to have a high affinity for bone and cartilage and thus may have adverse musculoskeletal effects.

Sulfonamides are usually safe during pregnancy. However, long-acting sulfonamides cross the placenta and can displace bilirubin from binding sites. These drugs are often avoided after 34 wk gestation because neonatal kernicterus is a risk.

Tetracyclines cross the placenta and are concentrated and deposited in fetal bones and teeth, where they combine with Ca and impair development (see Table 2: Drugs in Pregnancy: Some Drugs With Adverse Effects During Pregnancy); they are not used from the middle to the end of pregnancy.

Last full review/revision December 2008 by Sean C. Blackwell, MD

Content last modified February 2012