Prevalence of Chlamydia trachomatis in Pregnant Iranian Women: A Systematic Review and Meta-Analysis

Pregnancy is a serious period in women´s lives, which is related to physiological changes, such as weakening the immune system (1, 2). Reproductive tract infections are one of the most serious public health issues in developed and developing countries (3). Chlamydia trachomatis is one of the most common sexually transmitted diseases worldwide (4). Colonization of Chlamydia trachomatis in the reproductive tract of pregnant women causes complications such as infertility, chronic pelvic pain, ectopic pregnancy, premature rupture of membranes (PROM), prematurity, spontaneous abortion, and perinatal mortality (5, 6). The prevalence of Chlamydia trachomatis infection is currently increasing throughout the world. The treatment costs of Chlamydia trachomatis infection is estimated to be more than 2 million US dollars. Diagnostic costs are much lower than treatment costs. Therefore, timely diagnosis and screening can decrease the prevalence of reproductive tract infections and reduce treatment costs of this disease (7).

The level of immunity in the body decreases during pregnancy (2). A weak immune system increases the risk factor for the entrance of infectious agents into the vagina. Ureaplasma urealyticum and Mycoplasma hominis are genital mycoplasmas that can be detected in the lower genitourinary tract of sexually active women as a result of colonization of the genital tract through sexual contact (5). These microorganisms can affect each part of the urogenital system and cause infection (8).

These microorganisms have an important role in infections and potential complications during pregnancy. Therefore, it is necessary to be aware of prevalence patterns to plan and screen pregnant women for these microorganisms. Several studies have been conducted in Iran to determine the prevalence of Chlamydia trachomatis, Mycoplasma hominis, and Ureaplasma urealyticum in pregnant Iranian women (9-21). Combining the previous results to present a general assessment seems necessary. A review of all relevant documents and presenting a general assessment based on systematic review and meta-analysis studies can provide a more detailed picture of the dimensions of this problem in pregnant women (22-24). Therefore, we have conducted the present meta-analysis women from Iran.

Awareness of the prevalence pattern and screening for diseases that affect the health of the mother and fetus is necessary during pregnancy. The present study is the first systematic review to assess the prevalence of Chlamydia trachomatis, Mycoplasma hominis, and Ureaplasma urealyticum in pregnant Iranian women.

We have determined the prevalence of Chlamydia trachomatis in 11 surveyed articles that had a sample size of 2864 pregnant Iranian women to be 8.74% (95% CI: 5.40-13.84). The prevalence of this disease is 10.1% in China (31), 10.5% in Saudi Arabia (32), and 35% in India (33). However, the results of the present study are similar to those reported in Scotland (34).

The prevalence of Chlamydia trachomatis in some studies was higher than the present study (35, 36). On the other hand, the results of other studies were in the same range as the present study (37, 38), though not exactly identical. Inconsistent results with the present study might be due to cultural differences, social and religious norms, and mean age of the studied populations. The high prevalence of this infection in women age 20 and above might be due to early onset of sexual intercourse, numerous pregnancies, and the use of oral contraceptives (39, 40). Women with vaginal secretions and inflammatory changes in cervical cytology are more prone to infection and should be examined by their gynecologists (41). Several documents have demonstrated that dysuria, vaginal discharge, and lower abdominal pain may be clinical symptoms of this infection (41, 42), which are more common in pregnant women.

Age (particularly 18-27 years) and socioeconomic conditions such as an urban residence or low income (43) are among the risk factors for Chlamydia trachomatis in pregnant women. A study in Japan has reported a significantly high prevalence of Chlamydia trachomatis in primiparous pregnant women (44).

Recent studies report a significant relationship between Chlamydia trachomatis infection to preterm delivery (5, 45). The importance of Chlamydia trachomatis for midwives is due to the ability of this microorganism to cause urethritis, cervicitis, preterm births, PROM, and neonatal infections as the baby passes through the birth canal, in addition to abortion, maternal mortality, and stillbirth. Repeated screening tests in the first prenatal examination and during the third trimester of pregnancy, along with successful treatment with erythromycin can reduce the complications of pregnancy according to the American College of Obstetricians and Gynecologists (5, 6, 45, 46).

These bacteria can be easily detected by cell culture and serological methods that use micro-immunofluorescence techniques, ELISA, the complement fixation test (CFT), antigen detection methods, molecular methods (DNA hybridization, nucleic acid amplification techniques), and direct cytological methods (Giemsa, Gimenez, and hematoxylin stains) (25, 26). The best and most cost-effective method to determine whether the infection during pregnancy is acute or chronic the ELISA test (47, 48). In the present study, we have noted that the prevalence of Chlamydia trachomatis according to PCR results was not significantly more than ELISA (P=0.082).

The prevalence of Mycoplasma hominis in pregnant Iranian women from 4 studies was 2 to 22.8% (17-20). The prevalence of Ureaplasma urealyticum in Iranian pregnant women was 9.1 to 19.8% (16-18). Meta-analysis was not performed on the prevalence of Mycoplasma hominis and Ureaplasma urealyticum because of a scanty number of studies. Therefore, we recommend conducting more research in this area for future studies. Mycoplasma hominis had the following prevalence in other countries: 3.7% (Poland), 31.5% (Portugal), 11.2% (Japan). Ureaplasma urealyticum had the following prevalence in other countries: 29.8% (Poland), 27.8% (Portugal), and 8.7% (Japan) (49-51). These results did not agree with the present study, which might be due to cultural differences, social and religious norms, and the mean age of the studied populations.

Mycoplasma hominis is isolated from the vaginal secretions of 15-70% of women. Ureaplasma urealyticumis is isolated from the vaginal secretions of 40-95% of women (8, 52-56). Mycoplasma hominis and Ureaplasma urealyticumis are transferred to the fetus during pregnancy or normal vaginal delivery. They are often associated with cervicitis, vaginitis, pyelonephritis, pelvic inflammatory disease, postpartum septicemia, uterine infections, meningitis, PROM, postpartum fever, preterm delivery, and low weight premature birth (8, 57, 58). Most premature births for women with these two infections happen before the 34th week of pregnancy (59, 60). However, no significant relationship has been found between these infections and adverse effects on pregnancy in some studies (51). Studies conducted on Mycoplasma hominis have demonstrated that it caused adnexal lesions but not salpingitis (53). Ureaplasma urealyticum is the main cause of non chlamydial and nongonococcal urethritis, chorioamnionitis, cervicitis, vaginitis, sepsis and preterm delivery. Moreover, it may cause pneumonia, meningitis and even death of the infant as the baby passes through the birth canal (56). The role of Ureaplasma urealyticum has not been specified (54). PCR is often used to diagnose this infection in Iran. However, the molecular technique has also been used in some studies in Iran (61). Therefore, considering the fact that failure to diagnose, prevent, and treat these infections leads to dangerous complications, it is necessary to identify these bacteria, particularly in pregnant women (53, 62).

Factors that increase the prevalence of prenatal infections in women include young age (adolescents and young adults); use of an intrauterine device (IUD); low level of education, unemployment, and low income; multiple sex partners; not using a condom, diaphragm or spermicide; lack of attention to individual health care for both men; and women and smoking, alcohol consumption, and drugs (25, 63, 64).

Several meta-analysis studies in Iran have focused on other infections in pregnant women and reported the following results: prevalence of urinary tract infection (11.2%) (65), hepatitis B (2%) (66, 67), and Helicobacter pylori (45.9%) (68, 69). According to Ahmadi et al. (70), the prevalence of urogenital mycoplasmas in the male population was 11.1% (95% CI: 7.4-16.4) and 12.8% (95% CI: 9.8-16.5) in females, which was high. Hence, Chlamydia trachomatis is one of the most common infections in pregnant Iranian women. Determining the causes of these infections and methods of prevention should be among the medical priorities for pregnant Iranian women to ensure the health of the next generation.

The limitations of the study included the failure to search using a combination of words in internal databases due to low sensitivity and the inability to perform further subgroup analysis because of the limited number of studies.

Future case-control studies to determine the role of various risk factors in Iranian societies seems necessary.

The high prevalence of reproductive tract infections among pregnant Iranian women necessitates screening these women as a preventive measure. Therefore, timely recognition and treatment of this disease can prevent maternal and fetal complications.