How does chlamydia impact pregnancy?

The days of sexually transmitted infection (STI) scare campaigns have died down in recent years because most STIs are now easily treatable with antibiotics. But there is a particular danger in STIs that go untreated—which is more common than you'd think because many have vague symptoms or none at all. Not treating chlamydia can cause serious complications in both men and women. In women, it can cause infertility, preterm labor, and negative impacts on a newborn's health. 

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Chlamydia is an STI caused by the Chlamydia trachomatis bacterium. According to the Centers for Disease Control and Prevention (CDC), it's the most commonly reported bacterial STI in the United States. In 2018, the CDC estimates that four million chlamydia infections occurred. Many cases are not reported because most people infected with chlamydia have no symptoms and do not get tested. It's estimated that one in 20 sexually active young women aged 14–24 has chlamydia (CDC, 2021).

Chlamydia spreads through vaginal, oral, or anal sex, and ejaculation doesn't have to occur for it to be transmitted. Chlamydia can also be spread from mother to infant during childbirth.

Chlamydia is known as the "silent" STI. Most people infected with chlamydia, including pregnant women, have no symptoms and seem normal upon physical examination. According to the CDC, only 10% of men and 5% to 30% of women who test positive for a chlamydia infection will develop symptoms (CDC, 2021).

The symptoms of chlamydia are similar in pregnant or nonpregnant biological females. In most cases, chlamydia infects the cervix first, causing vaginal discharge. The bacteria can also irritate the urethra (the tube that allows urine to leave the body), resulting in urethritis, which is often signaled by pain while urinating. Untreated chlamydia can spread to the uterus, fallopian tubes, and ovaries, causing abdominal pain or pelvic pain and pelvic inflammatory disease (PID) (Hsu, 2019).

Some people develop an eye infection, called chlamydial conjunctivitis (a form of pinkeye). The symptoms include redness, infection, and discharge. Chlamydia can also infect the rectum, either through receptive anal sex or the spread of bacteria from the cervix or vagina. This might produce pain, discharge, or bleeding or cause no symptoms at all. Lastly, you can develop oral chlamydia if you come in contact with your partner’s infected vagina, anus, or penis; most of the time there are no symptoms (Hsu, 2019).

Untreated chlamydia can cause several complications in both pregnant and nonpregnant women, including pelvic inflammatory disease (PID), which is inflammation of the cervix, uterus, ovaries, and fallopian tubes. 

PID can cause scarring of the fallopian tubes, which increases the risk of future ectopic pregnancy (egg implantation outside of the uterus). If the scarring blocks the tube, the fertilized egg can’t get to the uterus and begins to grow in the fallopian tube. Since the fallopian tubes don’t have room for the embryo to grow, the tube can burst, causing internal bleeding, shock, and blood loss that can be fatal. 

Ectopic pregnancy is not the only potential complication from chlamydia. You can get a chlamydial infection at any time during pregnancy. Around 2–20% of pregnant women have a chlamydial infection, even though most don’t realize it. Unfortunately, if you have chlamydia while pregnant, you have an increased risk of premature rupture of the membranes (water breaking too soon), preterm (premature) delivery, and having a baby with a low birth weight (Hsu, 2019).

In 50–70% of cases, untreated chlamydia passes from the mother to the infant during childbirth. This can lead to conjunctivitis or pneumonia in the newborn (Hammerschlag, 2018).

Pregnant women in the U.S. are routinely screened for chlamydia and other STIs at their initial prenatal visit (Ghanem, 2020). If your cultures come back positive, your healthcare provider will recommend antibiotic treatment to decrease your risk of complications. 

Azithromycin (brand name Zithromax) is the recommended treatment for chlamydia infection while pregnant. Other antibiotics like amoxicillin and erythromycin are also options (Mohseni, 2021). Doxycycline, one of the first-line antibiotics for treating chlamydial infection in nonpregnant people, is not used in pregnancy because it may affect the growth and development of teeth, causing permanent discoloration (DailyMed, 2019). 

The only absolute way to avoid STIs is to avoid sexual contact. If you’re sexually active, you could be infected with chlamydia, even if you are pregnant. The best way to prevent chlamydia is to use condoms consistently or to have sex with a partner who's been tested and knows they're uninfected. All pregnant women should be screened for chlamydia to prevent complications. Talk to your health care provider about any questions or concerns you may have about chlamydia and your pregnancy. 

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

May 14, 2021

Written by

Mike Bohl, MD, MPH, ALM

Fact checked by

Chimene Richa, MD

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About the medical reviewer

Chimene Richa, MD

Dr. Richa is a board-certified Ophthalmologist and medical writer for Ro.