Chlamydia trachomatis Prevalence and Risk Behaviors in Parturient Women Aged 15 to 24 in Brazil : Sexually Transmitted Diseases

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Chlamydia trachomatis Prevalence and Risk Behaviors in Parturient Women Aged 15 to 24 in Brazil

Pinto, Valdir Monteiro MD, MSc*†; Szwarcwald, Célia Landmann PhD; Baroni, Carla BSc; Stringari, Lorenzo Lyrio BSc; Inocêncio, Lilian Amaral BSc*; Miranda, Angélica Espinosa MD, PhD

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Sexually Transmitted Diseases 38(10):p 957-961, October 2011. | DOI: 10.1097/OLQ.0b013e31822037fc
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Chlamydia trachomatis (CT) is one of the sexually transmitted infections (STI), and has great effect on sexual and reproductive health.1,2 CT and Neisseria gonorrhoeae (NG) are responsible for genitourinary infections, pelvic inflammatory disease, chronic pelvic pain, fallopian tube infertility, ectopic pregnancy, and are also associated with cervical cancer.3,4 CT most frequently affects people <20 years of age.1 Infection during pregnancy-childbirth cycle can result in premature labor, premature rupture of the membranes, and low birth weight.5–7 CT also have repercussions for the fotus, which may be infected through the vaginal tract and suffer conjunctivitis and pneumonia.8

In women, diagnosis of CT infection is difficult in developing countries because of inadequate infrastructure laboratories to perform diagnostic tests. CT is asymptomatic in approximately 70% to 80% of cases, and remains undetected and thus untreated. This represents one of the principal difficulties for its control.9 One of the most important risk factors identified in previous studies is being young, that is, less than 25 years of age.9–17

In Brazil, the national prevalence of CT infection has not been estimated before. Previous local studies in Brazil have shown high frequency of CT in young women.16,17 The scarcity of data is due to several factors: the lack of clinical symptoms that influences the identification of infected individuals and the problems of access to laboratory tests. These tests are expensive and rarely performed in Brazilian public health services. In private healthcare services, CT investigation is only undertaken in symptomatic cases or when a sexual partner reports the diagnosed infection. Prenatal care coverage in the country is about 96.5% and screening for STI is performed routinely only to diagnose HIV and syphilis.18

The purpose of this study was to estimate the national prevalence of CT infection and its association with NG in parturient women aged 15 to 24 years attending Brazilian public maternity units. This study provides useful information for the elaboration of public health policies on CT screening and the building of indicators for monitoring the strategies to prevent this infection in young women.


A cross-sectional study was conducted in 2009 among parturient women attending Brazilian public hospitals. Parturient women attending selected maternity units in 5 geographic macro-regions of Brazil from March to November 2009 were invited to take part in the study.

Data Collection

Each participant was interviewed face-to-face by a trained health professional A face-to-face questionnaire was used for collection of sociodemographic data (age, race/color, schooling, marital status, and family income); clinical data (gestational age, number of pregnancies, number of childbirths, number of miscarriages/abortions, antenatal examinations performed); sexual data (age at first sexual intercourse, prior history of STI, gynecological complaints, number of sex partners in the last year and since their first sexual intercourse); and STI/HIV risk behavior (drug use, sex in exchange for money/goods, and information about sex partners regarding a history of blood transfusions, injecting drug use, bisexual practices, and history of imprisonment). Family income was measured in minimum Brazilian wages (MBW); 1 MBW in 2009 was approximately US$250.

Laboratory Tests

A 20-mL urine sample was obtained from the first amount of urine passed, with the recommendations of no prior genital cleansing and a minimum period of two hours without urinating before sample collection. Samples were analyzed in a semiautomated system called COBAS Amplicor CT/NG (Roche Molecular Systems, Branchburg, NJ) for qualitative in vitro detection of CT and NG, as per the manufacturer's instructions at the Molecular Biology Laboratory of the Infectious Diseases Unit of the Federal University of Espírito Santo.

Calculation of the Sample Size

The sample size was calculated to estimate the national and regional prevalence rate in parturient women aged 15 to 24 years, with a 95% confidence interval (CI) for 1.5% bilateral size. A 10% prevalence rate was taken as the basis for calculating the sample size.17 The calculated sample size was 1536 and, considering a 20% loss and a sampling design effect of 1.3, a final sample size of 2400 parturient women was obtained.


Sampling was performed in 2 stages. In the first stage, 24 public health system maternity units were randomly chosen, with probability proportional to size, established by the number of childbirths in the year before the study. The choice of the maternity units was stratified by geographic macroregion (North, Northeast, Midwest, Southeast, and South) with proportional allocation to the number of childbirths in the year before the commencement of the study of the year 2009. A total of 100 women were selected in each health establishment. At the time of their admission for childbirth, an interview was performed with regard to filling a designed questionnaire and providing urine samples.

Statistical Analysis

Data were analyzed using the SPSS—data entry statistical program (Statistical Package for the Social Sciences) version 17.0. The data collected were weighted using the number of live births in each geographical region in the year 2008. A preliminary analysis was performed using exploratory techniques on the data, to check the distribution patterns and trends of the principal variables. Bivariate analysis was then performed to check for the presence of association between the variables. χ2 tests were used for proportion differences and Student t tests and variance analysis were used for testing differences between mean values. To estimate associations with the presence of CT infection, the odds ratio (OR) was used as a measure of association, estimated with a 95% CI. Multivariate analysis was performed to estimate joint effects of independent variables, through the use of logistic regression models.

Ethical Aspects

This project was submitted to the Research Ethics Committee of the Health Sciences Centre of the Federal University of Espírito Santo (Committee approval number 112/07) and to the ethical committee of each maternity unit taking part in the study. All selected women were invited to take part voluntarily in the study and those who accepted signed a written consent form. Those who were diagnosed as being infected received treatment in accordance with the Brazilian guidelines for Sexually Transmitted Diseases Control.18


Of the sample of 2400 parturient women, a total of 2071 (86.3%) were included in the study. No specific information was gathered about nonrespondents. Some of them presented with bleeding during sample collection and were excluded (3.7%), some declined to participate because they were in pain (2.0%), and some accepted to participate but samples were lost during transportation (unfrozen, shed, and/or mixed) (8.0%). The mean age was 20.2 years (standard deviation [SD] = 2.69) and mean of formal education was 8 years (SD = 2.4).

The prevalence rate of CT infection was 9.8% (95% CI: 8.5%–11.1%) and NG was 1.0% (95% CI: 0.6%–1.4%). Four percent of women with CT had a positive test results for NG. Table 1 shows the distribution of CT prevalence rates in the macroregions of Brazil. The highest rate was found in the Northern region (14.1%) and the lowest rate in the Southern region (6.9%).

Prevalence of Chlamydia trachomatis Infection in Brazilian Parturient Women, by Geographical Region (N = 2071)

Table 2 shows CT results by sociodemographic characteristics. Women with positive test results were younger (15–19 years) (54.0% vs. 38.1%, P = 0.046); reported not living maritally with their partners (38.6% vs. 26.6%, P = 0.000), and were poorer (had income less than 4 MBW) (97.0% vs. 92.9%, P = 0.025).

Sociodemographic Characteristics of Parturient Women Attending Brazilian Public Maternity Units and Association With C. trachomatis (N = 2071)

The age of onset of sexual activity ranged from 9 to 24 years, with the mean of 15.6 years (SD = 2.7). As shown in Table 3, women with Chlamydia diagnosis reported to be sexually active earlier—before 15 years of age (41.6% vs. 31.9%, P = 0.007), have more than 1 sexual partner in the last year (8.9% vs. 4.7%, P = 0.016), and more than 1 sexual partner in their lifetime (72.8% vs. 63.1%, P = 0.007). They also reported illicit drug use more frequently (10.4% vs. 5.6%, P = 0.012), including injecting drug use (2.0% vs. 0.5%, P = 0.040). No differences were found in terms of prior history of STI (P = 0.393) or prostitution (P = 0.665).

Behavioral Characteristics of Parturient Women Attending Brazilian Public Maternity Units and Association With C. trachomatis (N = 2071)

Table 4 describes CT prevalence rate by clinical characteristics. Parturient women with a positive CT test result gave birth prematurely more frequently (21.8% vs. 16.1%, P = 0.046) and had a higher number of positive NG tests (4.0% vs. 0.6%, P < 0.001) when compared to the women without CT. Attending to 6 or more antenatal care appointments were significantly less among women with CT (3.7% vs. 54.6%, P = 0.016). Pap smear screening during the preceding year was also significantly less in women with CT (37.1% vs. 47.8%, P = 0.004).

Clinical Characteristics of Parturient Women Attending Brazilian Public Maternity Units and Association With C. trachomatis (N = 2071)

The factors associated with CT in the multivariate logistic regression analysis were as follows: age ranging from 15 to 19 years (OR = 1.6 [95% CI: 1.15–2.17]); onset of sexual activity before 15 years old (OR = 1.4 [95% CI: 1.04–6.24]); more than 1 sexual partner in their lifetime (OR = 1.6 [95% CI: 1.13–2.26]); Pap smear screening more than 1 year ago (OR = 1.5 [95% CI: 1.08–2.05]); and NG coinfection (OR = 7.6 [95% CI: 3.05–19.08]) (Table 5).

Multivariate Analysis of Factors Associated With C. trachomatis Infection in Parturient Women Attending Brazilian Public Maternity Units, 2009


This is the first population-based study at the national level in Brazil to determine the prevalence of CT in young pregnant women. We identified a prevalence rate of 9.8%.

Previous local studies in Brazil have shown similar results regarding the prevalence of CT in pregnant and adolescent women. A study performed in the city of Vitória, Espírito Santo, identified CT in 12.2% of sexually active female adolescents.19 Menezes et al.20 found 7.8% of CT in pregnant women in Recife, Pernambuco, and a study of female adolescents in Goiânia, Goiás, reported a 19.6% of CT.16 A study performed in 6 cities using a convenience sample reported a 9.4% of CT among pregnant women.17

Our findings are also in agreement with other studies performed among asymptomatic young women in other countries. Rates from 1.7% to 17% were described in different European countries12,13 and from 4.4% to 15.5% in United States.9,21 Other studies reported 10.1% of CT in pregnant women in China,22 8% in Botswana,14 and 7.7% in Venezuela.15

In agreement with other authors, our results also showed an association between CT and age, with higher frequency among the youngest group of women,9,10,13–17,23–25 as well as among women who reported having had more than 1 sex partner in their lifetimes,10,16,17 and in those with NG coinfection.9,24 These observations highlight that a systematic evaluation needs to be performed concerning risk factors related to sexual behavior in this group. Clinical studies of behavioral interventions, services for sex partners, and treatment services have shown promising results in reducing the risk of bacterial infection, duration of infection, and number of sexual partners.25

We found that Chlamydia infection showed an association with lack of yearly Pap smear screening. This may be explained by the fact that women who take care of their own health have a greater chance of having infections diagnosed and treated earlier, as suggested by Wilson et al.,12 than women who do not seek healthcare.

Although a cross-sectional study is not ideal for determining risk factors, its application is justified. CT prevalence and risk factors in young women at child-bearing age is important to demonstrate the susceptibility of this population group to complications caused by this infection during the pregnancy-childbirth cycle and puerperium. Given the low prevalence of some risk factors in this sample, it is possible that the number of women studied was not sufficient to find statistical association between some independent variables and Chlamydia infection. The possibility of biased answers cannot be rule out because of the general tendency to give socially acceptable replies in face-to-face interviews. Also, we only included public hospitals and therefore cannot draw conclusions on private ones; however, it is important to say that about 70% of the childbirths take place in public hospitals.

Bacterial STI have been neglected in recent times due to an increase of viral STI epidemic, especially HIV, which can lead to the misguided suggestion that these agents are diseases of the past, of less importance, and of limited interest to professionals providing healthcare. On the contrary, as demonstrated recently, these infections are a huge burden for health and the economy accounting for 17% of economic losses, mainly in developing countries, caused by the health-disease binomium.26

Nevertheless, great progress has been achieved in STI prevention by using, in the majority of cases, multiple approaches such as, for example, adding a screening program to prevention strategies for risk populations, which has been shown to be cost effective.27 Thus enabling early diagnosis and timely treatment and, therefore, reducing morbidity caused by highly asymptomatic diseases such as Chlamydia infections.

Given the well-established association between Chlamydia infection and pelvic inflammatory disease, fallopian tube damage and scarring, infertility, ectopic pregnancy, as well as conjunctivitis and pneumonia in newborn babies, efforts to reduce this infection among teenagers and young adults can produce an important effect on morbidity arising from this disease. A recent US Preventive Services Task Force publication on measures to prevent STIs emphasized the importance of introducing the investigation of Chlamydia infection in all pregnant women aged <24 years.28

Our results show high CT prevalence in young parturient women in Brazil. This suggests that diagnostic tests for this infection should be included in screening programs for young pregnant women. Timely diagnosis and treatment could provide peace of mind to women worried about the outcome of their current pregnancy and the future of their sexual and reproductive health. As most cases are asymptomatic, a screening program is one of the important means for identifying undiagnosed infection and to provide earlier treatment to these women and their sexual partners.


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