Can Chlamydia Cause Miscarriage in Early Pregnancy?
Explore the link between chlamydia and early pregnancy loss, including its impact on reproductive health and the importance of screening for prevention.
Chlamydia is one of the most common sexually transmitted infections (STIs) and can have serious health consequences if left untreated. While it is often linked to infertility and pelvic inflammatory disease, its impact on early pregnancy is a growing concern.
Understanding how chlamydia contributes to miscarriage is crucial for prevention and treatment during pregnancy.
How It Spreads
Chlamydia trachomatis, the bacterium responsible for chlamydia infections, spreads primarily through sexual contact, including vaginal, anal, and oral intercourse. It thrives in the mucosal linings of the reproductive and urinary tracts, often without causing symptoms. This asymptomatic nature allows the infection to spread unknowingly. According to the Centers for Disease Control and Prevention (CDC), an estimated 70–80% of infected women and 50% of infected men experience no symptoms, increasing the risk of transmission.
Once in the reproductive tract, Chlamydia trachomatis adheres to epithelial cells and invades them, initiating intracellular replication. The bacterium exists in two forms: the infectious elementary body, which spreads the infection, and the replicative reticulate body, which multiplies within host cells. This intracellular lifestyle enables it to evade immune detection and persist for extended periods. Studies published in The Lancet Infectious Diseases indicate that untreated infections can last for months or even years.
Beyond sexual transmission, vertical transmission from mother to child during childbirth is another risk. A newborn can contract the bacterium while passing through the birth canal, leading to neonatal conjunctivitis or pneumonia. Research in JAMA Pediatrics has shown that up to 50% of infants born to infected mothers develop conjunctivitis, while 5–30% develop pneumonia, emphasizing the need for early detection and treatment during pregnancy.
Mechanisms in Reproductive Tissues
Once Chlamydia trachomatis establishes an infection, it disrupts reproductive tissues. The bacterium primarily targets epithelial cells in the endocervix and upper reproductive tract, entering through receptor-mediated endocytosis. Inside, it resides in a membrane-bound vacuole called an inclusion, shielding itself from immune responses. Studies in Nature Reviews Microbiology show that chlamydial inclusions manipulate host cell signaling, delaying apoptosis and prolonging bacterial survival.
As the infection progresses, chlamydia weakens the protective barrier of the endocervix and fallopian tubes by degrading tight junctions between epithelial cells. This increases the risk of bacterial spread and ascending infections into the uterus. Research in The Journal of Infectious Diseases has found that chronic chlamydial infections damage epithelial cells through bacterial secretions that degrade extracellular matrix components. This damage exposes underlying tissues to inflammation, worsening tissue injury.
Chlamydia also alters the extracellular matrix, leading to excessive collagen deposition and fibrosis. This fibrotic remodeling, particularly in the endometrium and fallopian tubes, can impair implantation and early pregnancy. A meta-analysis in Human Reproduction Update found that women with a history of chlamydial infection had higher rates of endometrial fibrosis, which may interfere with embryo attachment and placental development.
Potential Contribution to Miscarriage
The presence of Chlamydia trachomatis in reproductive tissues has been linked to pregnancy complications, including early miscarriage. Infection-induced changes in the uterine environment can disrupt implantation and embryonic development. Research in Human Reproduction has shown that women with a history of chlamydial infection have higher rates of implantation failure and early pregnancy loss.
The bacterium also affects vascular remodeling in the uterus, which is critical for placental development. Proper transformation of maternal spiral arteries supports fetal growth, but chlamydial infections have been associated with impaired trophoblast invasion, a key step in placental formation. Studies in Placenta suggest that insufficient remodeling of uterine blood vessels can create a hostile intrauterine environment, increasing the risk of miscarriage.
Chronic infections can also lead to long-term endometrial dysfunction. Persistent chlamydia exposure may alter gene expression related to embryo implantation and uterine receptivity. A retrospective analysis in Fertility and Sterility found a higher prevalence of past chlamydial infections in individuals with recurrent pregnancy loss, reinforcing the link between infection and miscarriage risk.
Testing and Screening Methods
Detecting Chlamydia trachomatis during pregnancy requires accurate screening methods. Nucleic acid amplification tests (NAATs) are the most sensitive diagnostic tools, detecting bacterial DNA or RNA in urine samples or cervical and vaginal swabs. According to the CDC, NAATs have a sensitivity exceeding 95%, making them effective for identifying asymptomatic infections.
Routine chlamydia screening is recommended during the first prenatal visit, especially for individuals under 25 or those with risk factors such as multiple sexual partners or a history of STIs. Repeat testing in the third trimester may be advised for those at continued risk to prevent perinatal transmission. The U.S. Preventive Services Task Force (USPSTF) supports these guidelines, emphasizing that early detection and antibiotic treatment with azithromycin or amoxicillin can significantly reduce pregnancy complications.
Preventive Measures
Preventing chlamydia-related pregnancy complications starts with limiting exposure to the infection. Consistent condom use is one of the most effective ways to reduce transmission. While not foolproof, studies in Sexually Transmitted Diseases indicate that condoms lower chlamydia transmission rates by 50–60%. Regular STI screening, particularly before pregnancy, is also essential. The American College of Obstetricians and Gynecologists (ACOG) recommends routine testing for sexually active individuals, particularly those under 25 or with multiple partners.
For pregnant individuals, early prenatal care is crucial. Screening in the first trimester allows for timely antibiotic treatment, which effectively clears the infection and reduces adverse pregnancy outcomes. Azithromycin and amoxicillin are considered safe during pregnancy and eliminate Chlamydia trachomatis in over 95% of cases. Partner treatment is equally important to prevent reinfection. The CDC advises that both partners complete the full course of antibiotics and abstain from sexual activity until treatment is finished. These measures help reduce the risk of chlamydia-related pregnancy complications.