Many sexually transmitted infections are associated with adverse pregnancy outcomes. The Centers for Disease Control and Prevention recommends screening all pregnant women for human immunodeficiency virus infection as early as possible. Treatment with highly active antiretroviral therapy can reduce transmission to the fetus. Chlamydia screening is recommended for all women at the onset of prenatal care, and again in the third trimester for women who are younger than 25 years or at increased risk.

Azithromycin has been shown to be safe in pregnant women and is recommended as the treatment of choice for chlamydia during pregnancy. Screening for gonorrhea is recommended in early pregnancy for those who are at risk or who live in a high-prevalence area, and again in the third trimester for patients who continue to be at risk.

The recommended treatment for gonorrhea is ceftriaxone 125 mg intramuscularly or cefixime 400 mg orally. Hepatitis B surface antigen and serology for syphilis should be checked at the first prenatal visit. Benzathine penicillin G remains the treatment for syphilis. Screening for genital herpes simplex virus infection is by history and examination for lesions, with diagnosis of new cases by culture or polymerase chain reaction assay from active lesions. Routine serology is not recommended for screening. The oral antivirals acyclovir and valacyclovir can be used in pregnancy. Suppressive therapy from 36 weeks’ gestation reduces viral shedding at the time of delivery in patients at risk of active lesions. Screening for trichomoniasis or bacterial vaginosis is not recommended for asymptomatic women because current evidence indicates that treatment does not improve pregnancy outcomes. (Am Fam Physician 2007;76:265-70, 272. Copyright © 2007 American Academy of Family Physicians.)

Infections during pregnancy affect the mother and often the child, either in utero or at the time of delivery. Many infections have been linked with increased risks of premature delivery and low birth weight, and associated morbidity and mortality. Because of these risks, the Centers for Disease Control and Prevention (CDC) has recommended screening for some sexually transmitted infections (STIs) at the first prenatal visit, then again in the third trimester for mothers at high risk . The CDC has also published recommendations for the treatment of STIs during pregnancy.

Screening

All women in the United States should be screened for human immunodeficiency virus (HIV) infection as early as possible during pregnancy. If the patient declines testing, the physician should discuss her objections and continue to strongly encourage testing. Other screening tests that are recommended for all pregnant women include those for hepatitis B, syphilis, and Chlamydia trachomatis. Women at risk should be tested for Neisseria gonorrhea and hepatitis C. Evidence does not support routine screening for bacterial vaginosis.

Women younger than 25 years and those who are at risk of chlamydia (e.g., those who have multiple sex partners) should be rescreened in the third trimester.1 Women who continue to be at risk of gonorrhea should also be rescreened in the third trimester.

When infection is detected, the physician must inform the mother, ensure adequate and safe treatment, and advise partner notification and treatment. In many states, cases of STI must be reported to the health department. Physicians should counsel the patient to use condoms and avoid sexual contact until her partner has been treated.

Chlamydia

C. trachomatis is the most common sexually transmitted bacterial pathogen in the United States, and as many as 5 to 15 percent of pregnant women are infected. Mother-to-child transmission of C. trachomatis can occur at the time of birth and may result in ophthalmia neonatorum or pneumonitis in the newborn, or postpartum endometritis in the mother. Some reports have linked chlamydia to low birth weight and preterm birth, but one study found no such association.

The nucleic acid amplification test (NAAT) is the preferred test for chlamydia because of its high sensitivity and specificity and its use on specimens obtained noninvasively. It can be performed using cervical or urine specimens. Nonamplified nonculture tests, such as the DNA probe test, remain an option when the NAAT is not available or is too expensive. Repeat testing three weeks after completion of therapy is recommended for pregnant women.

Tetracyclines are contraindicated in pregnancy because of the risk of bone and tooth abnormalities. Amoxicillin (500 mg orally three times per day for seven days) appears to be effective for microbiologic cure, but there are few data on its long-term effectiveness for neonatal infection.4 A randomized trial comparing azithromycin (Zithromax) in a single 1-g dose to erythromycin in a dosage of 500 mg every six hours for seven days found enhanced compliance, fewer gastrointestinal side effects, and equivalent effectiveness with azithromycin.5 No long-term safety studies on azithromycin in pregnancy have been published; however, azithromycin is U.S. Food and Drug Administration pregnancy category B and is recommended as first-line treatment for chlamydia in pregnancy. The single 1-g oral dose can be given in the office when compliance is a concern.

Gonorrhea

N. gonorrhea can be transmitted to the newborn from the mother’s genital tract at the time of birth and can cause ophthalmia neonatorum, systemic neonatal infection, maternal endometritis, or pelvic infection. The risk of transmission from an infected mother to her infant is between 30 and 47 percent.

Screening can be performed with a culture on Thayer-Martin media, which is recommended in a population with a low prevalence of infection.3 Nucleic acid hybridization tests of cervical specimens and NAATs of cervical specimens or urine are also used, with NAATs being the most sensitive and specific. Culture is the most widely available test and has the advantage of providing antimicrobial susceptibility. A repeat test is recommended in the third trimester for those at continued risk.

A Cochrane review of treatment for gonorrhea in pregnancy concluded that ceftriaxone (Rocephin) 125 mg intramuscularly and spectinomycin (Trobicin) 2 g intramuscularly have similar cure rates to oral amoxicillin plus probenecid. One randomized trial found cefixime (Suprax) 400 mg orally to be as effective as ceftriaxone 125 mg intramuscularly for the treatment of gonorrhea in pregnancy. The CDC recommends either of these as the treatment of choice for gonorrhea. There have been times when cefixime has been in short supply. Spectinomycin is rarely used because of the high volume required for the intramuscular dose.

Syphilis

Treponema pallidum, the cause of syphilis, is highly transmissible, even in the absence of any specific symptoms or clinical findings. Maternal syphilis has been associated with complications such as hydramnios, spontaneous abortion, and preterm delivery. Fetal complications such as fetal syphilis, fetal hydrops, prematurity, fetal distress, and stillbirth also occur. Neonatal complications can include congenital syphilis, neonatal death, and late sequelae.

Screening is performed with a blood test-the rapid plasma reagin or Venereal Disease Research Laboratories test-and confirmed with a fluorescent treponemal antibody serology and T. pallidum particle agglutination. A single serologic test is insufficient because false-positives occur with other illnesses.

If syphilis is diagnosed after 20 weeks’ gestation, ultrasonography should be performed to evaluate for fetal syphilis. Although fetal infection can be cured by treating the mother, treatment failure is much higher in the presence of fetal hepatomegaly, ascites, hydrops, polyhydramnios, and placental thickening, which are signs of fetal syphilis detected on ultrasonography.

Treatment has been with benzathine penicillin G. A Cochrane review concluded that although penicillin is effective for the treatment of syphilis in pregnancy and the prevention of congenital syphilis, the optimal treatment regimen is uncertain.20 The CDC recommends benzathine penicillin G, 2.4 million units intramuscularly, with desensitization in patients who are allergic to penicillin.

BARBARA A. MAJERONI, MD, and SREELATHA UKKADAM, MBBS
State University of New York at Buffalo, Buffalo, New York

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