STD Treatment During Pregnancy: What's Safe?

Most STIs can be safely treated during pregnancy, and treating them protects the baby as much as the parent. Chlamydia, gonorrhea, syphilis, trichomoniasis, herpes, and HIV all have pregnancy-safe regimens. The key change is the drug list: a few antibiotics, like doxycycline, are swapped for safer alternatives, and penicillin allergy is managed with desensitization rather than avoidance.

Why treating STIs in pregnancy protects the baby

Untreated infections during pregnancy don't just stay with the parent, many cross the placenta or pass to the newborn during delivery. Syphilis can cause stillbirth, bone deformities, and neurological damage in the baby; gonorrhea and chlamydia can cause eye infections and pneumonia after vaginal birth; HIV can transmit to the infant during pregnancy, labor, or breastfeeding. That's why everyone who is pregnant is screened for HIV and syphilis (and hepatitis B) early on, catching and treating these protects the baby USPSTF syphilis in pregnancy.

The other reason screening matters in pregnancy: most of these infections are silent. You can carry chlamydia or syphilis with no symptoms and still pass serious harm to a newborn. Screening is testing when you feel fine: it's how silent infections get caught, and how often you test is driven by your risk, not how you feel. If you're unsure when an exposure would even show up on a test, see when to test after exposure.

Chlamydia and gonorrhea: pregnancy-safe regimens

Chlamydia

Chlamydia in pregnancy is treated with azithromycin, an oral antibiotic considered safe across all trimesters. It's usually given as a single dose, which makes it easy to complete: important, since a half-finished course can leave the infection active at delivery. After treatment, clinicians typically retest later in the pregnancy to confirm the infection cleared and to catch reinfection from an untreated partner. Both partners need treatment, or the cycle repeats.

Gonorrhea

Gonorrhea is treated with ceftriaxone, given as a single injection. Cephalosporins like ceftriaxone are safe in pregnancy, and because gonorrhea and chlamydia often travel together, treatment frequently covers both at once. Untreated gonorrhea at delivery can cause ophthalmia neonatorum, a serious eye infection in the newborn that can threaten sight, which is exactly why screening sexually active women under a certain age every year is standard, even when nothing feels wrong USPSTF chlamydia & gonorrhea.

Syphilis: penicillin is the only recommended treatment

Syphilis is the one infection where the treatment really has no equal in pregnancy: penicillin, given by injection, is the only regimen proven to treat both the parent and the developing fetus. The alternatives used in non-pregnant adults, like doxycycline, are either unsafe in pregnancy or don't reliably cross the placenta to treat the baby.

So what happens if you're allergic to penicillin? You're not turned away, you're desensitized. Penicillin desensitization is a controlled, monitored process (usually in a hospital) where tiny, gradually increasing doses are given until your body tolerates a full treatment dose. It's done because no safe substitute treats congenital syphilis, the form passed to the baby, which can cause miscarriage, stillbirth, or lifelong damage to bones, brain, and organs. Timing matters: the earlier in pregnancy syphilis is found and treated, the more harm is prevented, which is part of why universal syphilis screening in pregnancy is recommended.

Trichomoniasis and bacterial vaginosis: metronidazole in pregnancy

Trichomoniasis (a common parasitic infection that causes itching, discharge, and irritation) is treated with metronidazole, an oral antibiotic that's considered safe in pregnancy. Bacterial vaginosis (BV), an imbalance of vaginal bacteria rather than a true STI, is also treated with metronidazole when symptomatic. Both conditions are linked to higher risk of preterm birth, so treating symptoms is worthwhile. Older worries about metronidazole early in pregnancy have largely not held up in newer evidence, and it remains the standard choice.

Herpes: antivirals late in pregnancy to prevent neonatal transmission

Genital herpes (HSV) is a lifelong virus, so the goal in pregnancy isn't a cure: it's preventing transmission to the newborn during delivery, which can cause severe, sometimes fatal neonatal herpes. Antiviral medications like acyclovir and valacyclovir are used and are considered safe in pregnancy. Clinicians often start suppressive antiviral therapy in the final weeks before the due date to reduce the chance of an active outbreak at delivery. If active genital lesions are present when labor begins, a cesarean delivery is usually recommended to avoid exposing the baby to the virus in the birth canal.

HIV: antiretroviral therapy throughout pregnancy

HIV in pregnancy is managed with antiretroviral therapy (ART) taken throughout the pregnancy. With consistent treatment that suppresses the virus, the risk of passing HIV to the baby drops dramatically, to very low levels. Additional steps, including medication for the newborn after birth and decisions about delivery and feeding, are layered on based on the parent's viral load. Because of how effective early treatment is, USPSTF recommends everyone aged 15 to 65 be tested for HIV at least once, and pregnant people are screened as a matter of routine USPSTF HIV screening. Starting treatment promptly doesn't only protect the infant: earlier hiv treatment can help prevention more broadly, by lowering the chance of passing the virus to anyone.

What's avoided in pregnancy

The biggest single rule is doxycycline. It's a first-line antibiotic for chlamydia and an alternative for syphilis in non-pregnant adults, but it's avoided in pregnancy because tetracyclines can affect fetal bone growth and stain developing teeth. This is the most common swap in pregnancy STI care, and it's why pregnant patients get azithromycin or penicillin instead. Here's how the standard choices line up:

Never stop or start a medication during pregnancy based on a chart alone: dosing, timing, and trimester all shape the actual prescription, and that's a conversation with your clinician.

When to see a clinician

If you're pregnant or planning to be, get screened early, and again later in pregnancy if you have ongoing risk. Make it routine: tie testing to a new partner, your prenatal intake, or any change in your relationship. Reasons to test sooner rather than wait for a routine visit include a new or multiple partners, a partner who tested positive, inconsistent condom use, or any genital symptoms. How often you screen should follow your risk, not your symptoms CDC STI screening. If exposure to the throat or rectum applies to you, ask specifically for those swabs, since a urine test alone misses them. You can get tested before or during pregnancy, and bring any positive result to your prenatal provider right away.

Keep exploring on EasySTD: confidential testing by state, STD incubation periods and Chlamydia testing.