Chlamydia is a common sexually transmitted infection that can cause long-term complications and, in pregnancy, may cause adverse maternal and neonatal outcomes. Antenatal care provides opportunities for testing women from population groups with a high prevalence of the infection.
8.5.1 BackgroundChlamydia is caused by the bacterium Chlamydia trachomatis. Genital chlamydial infection remains asymptomatic in at least 70% of women and the majority of infections probably clear spontaneously without morbidity (Geisler et al 2008; Rogers et al 2008). Complications that may arise for women include chronic pelvic pain, pelvic inflammatory disease, infertility and ectopic pregnancy.
Prevalence of chlamydia
- Rates of diagnosis of chlamydia — Chlamydia is the most common bacterial sexually transmitted infection in developed countries and the most frequently reported notifiable diagnosis in Australia, with over 62,000 diagnoses in 2009 (AIHW 2010). The rate of diagnosis of chlamydia continues to rise in both the non-Indigenous and Aboriginal and Torres Strait Islander populations, with increases between 2005 and 2009 of 59% and 10%, respectively (NCHECR 2010).
- Geographical distribution — Diagnoses of chlamydia in 2009 (NNDSS 2010) varied considerably by State/Territory, ranging from 210.5 per 100,000 population in NSW to 940.6 per 100,000 in the NT. Rates of diagnosis also vary considerably at the regional level (eg rates of diagnoses of between 740.9 and 2121.1 per 100,000 population have been reported in some areas of the Queensland, WA and the NT [NCHECR 2010]). The rate of diagnosis of chlamydia among the Aboriginal and Torres Strait Islander population resident in major cities in SA, Victoria and WA in 2009 was 3.5 times that among non-Indigenous people. Among Aboriginal and Torres Strait Islander people resident in remote and very remote areas in the NT, SA, Tasmania, Victoria and WA, the rate of diagnosis of chlamydia was at least 7 times that among non-Indigenous people (NCHECR 2010).
- Risk factors — Chlamydia is highly prevalent among younger people, with around 80% of all diagnoses being in young people (NCHECR 2010). Recent change in sexual partner is also a risk factor for chlamydia infection.
Risks associated with chlamydia in pregnancyChlamydia infection during pregnancy has been associated with adverse outcomes including higher rates of preterm birth (OR 1.6; 90% CI 1.01–2.5) and intrauterine growth restriction (OR 2.5; 90% CI 1.32–4.18) (John Hopkins Study Team 1989). Left untreated, it has also been associated with increased low birth weight and infant mortality (Ryan et al 1990).
Babies born to mothers who have cultured positive to C. trachomatis, may subsequently also culture positive (approximately 25%) and have been reported to have higher rates of neonatal conjunctivitis, lower respiratory tract infections and pneumonia (Schachter et al 1986; Preece et al 1989).
However, the NICE guidelines note that the causal link between chlamydia infection and adverse outcomes of pregnancy has not been established and the evidence remains difficult to evaluate in relation to neonatal morbidities (NICE 2008).
8.5.2 Chlamydia screening in pregnancy
Summary of the evidenceThe NICE guidelines reviewed the evidence on diagnostic accuracy and effectiveness of screening methods in identifying genital chlamydia and found no good evidence to support routine antenatal screening.
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Diagnostic accuracyThe evidence on diagnostic accuracy was limited to prospective cohort studies. The accuracy of antigen detection tests using endocervical specimens (Stamm et al 1984; Baselski et al 1987; Smith et al 1987) and of nucleic acid amplification tests using first-void urine and endocervical specimens (Thejls et al 1994; Andrews et al 1997; Garland et al 2000; Macmillan et al 2003; Renton 2006) was supported. While nucleic acid hybridisation test (DNA probe test) may be accurate the evidence is limited and of moderate quality (Yang et al 1991; Hosein et al 1992). Based on limited evidence, Gram staining (Asbill et al 2000) and Pap smear (Spence et al 1986) had insufficient accuracy to detect chlamydia.
Effectiveness of screeningReview of the effectiveness of screening in reducing adverse outcomes for the pregnancy and the neonate found limited evidence (one RCT [Martin et al 1997] and five cohort studies [Macmillan et al 1985; Black-Payne et al 1990; Cohen et al 1990; Ryan et al 1990; Rivlin et al 1997]) to indicate that treating chlamydia infection during pregnancy is effective in reducing the incidence of premature rupture of the membranes, preterm birth and low birth weight babies. There was no significant evidence to show that treating chlamydia infection during pregnancy leads to decreased incidence of adverse neonatal outcomes (conjunctivitis, pneumonia).
The literature review conducted to inform these Guidelines found no additional systematic reviews or RCTs to support or refute the findings presented in the NICE guidelines. However, there is additional information from systematic reviews and prevalence studies from 2008–2010 to suggest a specific population-based screening program (eg for those at highest risk). This evidence is discussed below.
Groups at higher riskThe Second National Sexually Transmitted Infections Strategy 2010–13 (DoHA 2010) identifies young people as a priority population for chlamydia screening, noting that in 2008, slightly more than 25% of all chlamydia infections were in the 15 to 19–year–old age group and nearly a further 65% were in 20 to 29–year–olds (NCHECR 2009).
Antenatal care provides an opportunity to discuss chlamydia testing with young women. Other considerations before testing is offered include whether the pregnancy is unplanned, the number of recent male sexual partners and antibiotic use in the previous 3 months (Chen et al 2009).
In the United Kingdom and the United States, chlamydia screening is recommended for pregnant women younger than 25 years (NICE 2008) and younger than 24 years (USPSTF 2007), respectively. Screening of young women in Australia is supported by:
- the known high prevalence of chlamydia in young people in Australia (Vajdic et al 2005; NCHECR 2009) and modelling that predicts a rapid reduction in prevalence through screening of people aged 25 years or younger (Regan et al 2008);
- estimates of the prevalence of chlamydia during pregnancy in young Australian women, which range from 3.2% (95% CI 1.8–5.9) among women aged 16–24 (n=403) (Chen et al 2009) to 13.7% among women aged 20 years or younger (n=212) (Cheney & Wray 2008); and
- qualitative research conducted as part of a prospective, cross-sectional study of pregnant women aged 16–25 years, which found a high level of acceptability of screening (Bilardi et al 2010).
Recommendation - Grade C16. Do not routinely offer chlamydia testing to all women as part of antenatal care. Routinely offer chlamydia testing at the first antenatal visit to pregnant women younger than 25 years.
While data are lacking to support routine screening, the prevalence of chlamydia is regionally variable and, in some areas, high prevalence may occur with that of other sexually transmitted infections, such as gonorrhoea. While screening of young women should take place in all areas, it is also important for health professionals to be aware of the rates of sexually transmitted infection in their community and develop local protocols accordingly.
Practice pointq. Testing for chlamydia and other sexually transmitted infections regardless of age should be considered for women who live in areas where their prevalence is high. An understanding of local prevalence will inform planning for population screening when this is indicated.
Type and timing of testAs discussed above, antigen detection (eg nucleic acid amplification tests) are accurate in diagnosing chlamydia. Study of the acceptability of these tests to young women found a preference for non-invasive methods. Both urine and vulval swab methods were highly sensitive, acceptable, and not affected by pregnancy status (Macmillan et al 2003). However, women may be unable to produce urine on demand and unrefrigerated transport time has been reported to influence sensitivity of testing. There is also preliminary evidence that urine has the lowest organism load when compared to endocervical, self-collected vaginal, and urethral specimens.
8.5.3 Practice summary — chlamydia screeningWhen — At the first contact with women younger than 25 and women in high prevalence areas
Who — Midwife; GP; obstetrician; Aboriginal and Torres Strait Islander health worker; multicultural health worker
- Discuss chlamydia — Explain the association between chlamydia and preterm birth and low birth weight, that tests for the infection are available and that it is easily treated with antibiotics.
- Take a holistic approach — If a woman tests positive for chlamydia, other considerations include counselling, contact tracing, partner testing, testing for other sexually transmitted infections and follow-up.
- Learn about locally available resources — Available testing services and support organisations will vary by location.
8.5.4 ResourcesSIGN (2009) Management of Genital Chlamydia Trachomatis Infection. A National Clinical Guideline. Edinburgh: Scottish Intercollegiate Guideline Network.
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8.5.5 ReferencesAIHW (2010) Australia’s Health 2010. Australia’s health series no. 12. Cat. no. AUS 122. Canberra: Australian Institute of Health and Welfare.
Andrews WW, Lee HH, Roden WJ et al (1997) Detection of genitourinary tract Chlamydia trachomatis infection in pregnant women by ligase chain reaction assay. Obstet Gynecol 89(4): 556–60.
Asbill KK, Higgins RV, Bahrani-Mostafavi Z et al (2000) Detection of Neisseria gonorrhoeae and Chlamydia trachomatis colonization of the gravid cervix including commentary by Mammel JB with author response. Am J Obstet Gynecol 183(2): 340–46.
Baselski VS, McNeeley SG, Ryan (1987) A comparison of nonculture-dependent methods for detection of Chlamydia trachomatis infections in pregnant women. Obst Gynecol 70(1): 47–52.
Bilardi JE, De Guingand DL, Temple-Smith MJ et al (2010) Young pregnant women’s views on the acceptability of screening for chlamydia as part of routine antenatal care. BMC Public Health 10: 505.
Black-Payne C, Ahrabi MM, Bocchini JA Jr et al (1990) Treatment of Chlamydia trachomatis identified with Chlamydiazyme during pregnancy. Impact on perinatal complications and infants. J Reproductive Med 35(4): 362–67.
Chen MY, Fairley CK, De Guingand D et al (2009) Screening pregnant women for chlamydia: what are the predictors of infection? Sex Transm Infect 85: 31–35.
Cheney K & Wray L (2008) Chlamydia and associated factors in an under 20s antenatal population’, Aust NZ J Obstet Gynaecol 48(1): 40–43.
Cohen I, Veille J-C, Calkins BM (1990) Improved pregnancy outcome following successful treatment of chlamydial infection. JAMA 263: 3160–63.
DoHA (2010) Second National Sexually Transmitted Infections Strategy 2010–13. Department of Health and Ageing. Commonwealth of Australia.
Garland SM, Tabrizi S, Hallo J et al (2000) Assessment of Chlamydia trachomatis prevalence by PCR and LCR in women presenting for termination of pregnancy. Sex Transm Infect 76(3): 173–76.
Geisler WM, Wang C, Morrison SG et al (2008) The natural history of untreated Chlamydia trachomatis infection in the interval between screening and returning for treatment. Sex Transm Dis 35(2): 119–23.
Hosein IK, Kaunitz AM, Craft SJ (1992) Detection of cervical Chlamydia trachomatis and Neisseria gonorrhoeae with deoxyribonucleic acid probe assays in obstetric patients. Am J Obstet Gynecol 167(3): 588–91.
John Hopkins Study Team (1989) Association of chlamydia trachomatis and mycoplasma hominis with intrauterine growth restriction and preterm delivery. The John Hopkins Study of Cervicitis and Adverse Pregnancy Outcome. Am J Epidemiol 129: 1247–51.
Macmillan JA, Weiner LB, Lamberson HV et al (1985) Efficacy of maternal screening and therapy in the prevention of chlamydia infection of the newborn. Infection 13(6): 263–66.
Macmillan S, McKenzie H, Templeton A (2003) Parallel observation of four methods for screening women under 25 years of age for genital infection with Chlamydia trachomatis. Eur J Obstet Gynecol Reprod Biol 107(1): 68–73.
Martin DH, Eschenbach DA, Cotch MF et al (1997) Double-blind placebo-controlled treatment trial of chlamydia trachomatis endocervical infections in pregnant women. Infect Dis Obstet Gynecol 5(1): 10–17.
NCHECR (2009) Annual Surveillance Report. National Centre for HIV Epidemiology and Clinical Research. Sydney: University of New South Wales.
NCHECR (2010) Bloodborne Viral and Sexually Transmitted Infections in Aboriginal and Torres Strait Islander People: Surveillance and Evaluation Report 2010. Sydney: National Centre in HIV Epidemiology and Clinical Research, The University of New South Wales.
NICE (2008) Antenatal Care. Routine Care for the Healthy Pregnant Woman. National Collaborating Centre for Women’s and Children’s Health. Commissioned by the National Institute for Health and Clinical Excellence. London: RCOG Press.
NNDSS (2010) Communicable Disease Surveillance: Preliminary Tables for 2009. For more information please visit Department of Health and Ageing website.
Preece PM, Anderson JM, Thompson RG (1989) Chlamydia trachomatis infection in infants: A prospective study. Arch Dis Childhood 64: 525–29.
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Regan DG, Wilson DP, Hocking JS et al (2008) Coverage is the key for effective screening of Chlamydia trachomatis in Australia. J Infect Dis 198(3): 349–58.
Renton A (2006) Chlamydia trachomatis in cervical and vaginal swabs and urine specimens from women undergoing termination of pregnancy. Int J STD AIDS 17(7): 443–47.
Rivlin ME, Morrison JC, Grossman JH (1997) Comparison of pregnancy outcome between treated and untreated women with chlamydial cervicitis. J Mississippi State Med Assoc 38(11): 404–07.
Rogers SM, Miller WC, Turner CF et al (2008) Concordance of chlamydia trachomatis infections within sexual partnerships. Sex Transm Infect 84(1): 23–28.
Ryan GM, Jr, Abdella TN, McNeeley SG et al (1990) Chlamydia trachomatis infection in pregnancy and effect of treatment on outcome. Am J Obstet Gynecol 162: 34–39.
Schachter J, Grossman M, Sweet RL et al (1986) Prospective study of perinatal transmission of Chlamydia trachomatis. JAMA 255: 3374–77.
Smith JW, Rogers RE, Katz BP et al (1987) Diagnosis of chlamydial infection in women attending antenatal and gynecologic clinics. J Clin Microbiol 25(5): 868–72.
Spence MR (1986) A correlative study of Papanicolaou smear, fluorescent antibody, and culture for the diagnosis of Chlamydia trachomatis. Obstet Gynecol 68(5): 691–95.
Stamm WE, Harrison HR, Alexander ER et al (1984) Diagnosis of Chlamydia trachomatis infections by direct immunofluorescence staining of genital secretions. A multicenter trial. Annals Int Med 101(5): 638–41.
Thejls H, Gnarpe J, Gnarpe H et al (1994) Expanded gold standard in the diagnosis of Chlamydia trachomatis in a low prevalence population: diagnostic efficacy of tissue culture, direct immunofluorescence, enzyme immunoassay, PCR and serology. Genitourin Med 70(5): 300–03.
USPSTF (2007) Screening for Chlamydial Infection: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med 147: 128–34.
Vajdic CM, Middleton M, Bowden FJ et al (2005) The prevalence of genital Chlamydia trachomatis in Australia 1997– 2004: a systematic review. Sex Health 2 (3): 169–83.
Yang LI, Panke ES, Leist PA et al (1991) Detection of Chlamydia trachomatis endocervical infection in asymptomatic and symptomatic women: comparison of deoxyribonucleic acid probe test with tissue culture. Am J Obstet Gynecol 165(5 Pt1): 1444–53.