Chlamydia trachomatis is an obligate intracellular bacterium that has several serotypes, including those that cause lymphogranuloma venereum (LGV). The most commonly encountered strains are those that attach only to columnar or transitional cell epithelium and cause cervical infection.

MATERNAL INFECTIONS.
Genital infection with C trachomatis is one of the most common sexually transmitted bacterial diseases in women of reproductive age (Miller and colleagues, 2004). They are also common in pregnant women, and their incidence depends on the demographical makeup of the population. In 2002, the median chlamydial infection rate among young women screened at prenatal clinics in 28 states was 10.1 percent (Centers for Disease Control and Prevention, 2003b). Risk factors for infection in pregnant women include age younger than 25 years, presence or history of other STD(s), multiple sexual partners, and a new sexual partner within 3 months (Centers for Disease Control and Prevention, 2002d).

Diagnosis. Cultures are expensive and less accurate than newer nucleic acid amplification tests, including PCR. Andrews and associates (1997) reported that a ligase chain reaction assay was both sensitive and specific for genitourinary infection in pregnant women.

Symptomatic Infection. Most pregnant women have asymptomatic infection, but some present with urethral syndrome, urethritis, or Bartholin gland infection (Peipert, 2003). Although mucopurulent cervicitis may be due to either chlamydial or gonococcal infection, or both, it may also result from the normal, hormonally stimulated endocervical glands with abundant mucus production. Other chlamydial infections not usually seen in pregnancy are endometritis, salpingitis, peritonitis, reactive arthritis, and Reiter syndrome.

Asymptomatic Infection and Pregnancy Outcome. Many investigators have examined the effects of asymptomatic chlamydial infection on pregnancy outcome, and its role remains controversial. Sozio and Ness (1998) found no association with increased abortion. Some investigators, but not all, have found that untreated cervical infection increases the risk of preterm delivery, prematurely ruptured membranes, and perinatal mortality.

Chlamydial infection appears to be associated neither with an increased risk of chorioamnionitis nor with pelvic infection after cesarean delivery (Blanco and colleagues, 1985; Gibbs and Schachter, 1987). Conversely, delayed postpartum uterine infection with C trachomatis has been described by Hoyme and associates (1986). The syndrome, which develops 2 to 3 weeks postpartum, is distinct from early postoperative metritis. It is characterized by vaginal bleeding or discharge, low-grade fever, lower abdominal pain, and uterine tenderness.

NEONATAL INFECTIONS.
There is vertical transmission to 30 to 50 percent of neonates delivered vaginally from infected women. Perinatal transmission to neonates can cause pneumonia, and C trachomatis is the most common identifiable infectious cause of ophthalmia neonatorum.

Conjunctivitis. Chlamydial eye infections are one of the most common causes of preventable blindness in developing countries. Symptomatic conjunctivitis tends to appear later (5 to 12 days) than disease caused by N gonorrhoeae (2 to 5 days). Tissue culture, direct fluorescent antibody tests, enzyme immunoassays, and nucleic amplification tests are sensitive and specific. None of the neonatal conjunctivitis prophylaxis regimens for gonococcal infection (e.g., silver nitrate, erythromycin, or tetracycline) is effective in the prevention of chlamydial conjunctivitis or pneumonia (Centers for Disease Control and Prevention, 2002d). When eye infection is identified, oral erythromycin, 50 mg/kg/day in four divided doses, is given for 10 to 14 days.

Pneumonitis. C trachomatis is a relatively common cause of afebrile pneumonia in infants at 1 to 3 months of age (Centers for Disease Control and Prevention, 2002d). Bilateral pulmonary infiltrates and chronic cough are often associated with poor weight gain.

PRENATAL SCREENING.
Routine antepartum screening for C trachomatis is a complex issue, although there is little evidence of its effectiveness in asymptomatic women who are not in high-risk groups (Kohl and colleagues, 2003; Peipert, 2003). Identification and treatment of infected pregnant women may prevent neonatal infections, but evidence of prevention of adverse pregnancy outcome is lacking. Therefore, neither the American College of Obstetricians and Gynecologists (2002), the American Academy of Pediatrics, nor the U.S. Preventive Services Task Force (2001) recommend routine screening of all pregnant women. However, these organizations do suggest routine screening for young women at increased risk. The Centers for Disease Control and Prevention (2002d) have recommended screening at the first prenatal visit and again in the third trimester for women younger than 25 years of age or for those who have new or multiple sex partners. In a study of 149 pregnant women with lower genital tract chlamydia, Miller (1998) found that 17 percent had recurrent chlamydial colonization after treatment. Accordingly, a second culture in the third trimester would seem reasonable in women with positive initial culture results or for those at high risk.

TREATMENT.
Currently recommended regimens for the treatment of chlamydial infection in pregnant women are shown in

Table 59-3. Erythromycin base, 500 mg orally four times daily for 7 days, is the primarily recommended regimen. For women who cannot tolerate erythromycin, the dose can be reduced by half and the duration of therapy doubled. Alternatively, the amoxicillin regimen may be given. In a randomized trial of treatment of C trachomatis in pregnancy, Silverman and associates (1994) reported cure rates of 82 percent for amoxicillin and 85 percent for erythromycin.

There have been a number of trials demonstrating the efficacy of azithromycin for chlamydial infection in pregnancy (Jacobson, 2001; Kacmar, 2001; Wehbeh, 1998, and all their colleagues). Comparable efficacy was reported by Adair and associates (1998) in a group of 106 women treated with erythromycin (93-percent cure) or azithromycin (88-percent cure). Of concern, Cooper and co-workers (2002b) noted an increased incidence of hypertrophic pyloric stenosis in neonates of mothers treated with nonerythromycin macrolides, however, there was no similar association with erythromycin exposure. These data are very limited, and azithromycin currently remains an alternative regimen (Adimora, 2002). Tetracyclines are avoided because of concerns regarding fetal dental discoloration. Erythromycin estolate is also avoided because of risks for maternal hepatic toxicity.