Published: July 2025 | Last updated: April 2026
Planning a pregnancy or already expecting? You are probably tracking ovulation, scanning prenatal vitamin labels, and rethinking caffeine. One thing that gets quietly skipped on the prep list is sexually transmitted infection screening. It is not about suspicion. It is about timing. Several of the infections that matter most during pregnancy are silent in their early stages, and the window to treat them safely is widest before delivery, not after.
This guide pulls together what current public-health guidance from the CDC, WHO, NHS, and the American College of Obstetricians and Gynecologists says about STI risk before conception, during prenatal care, and in the third trimester. It covers which infections threaten a pregnancy, why itching or unusual discharge during pregnancy deserves a second look, and how at-home rapid screening fits alongside prenatal care without replacing it.
Should I get tested for STIs before or during pregnancy?
Yes. The CDC recommends that all pregnant people are screened at the first prenatal visit for HIV, syphilis, hepatitis B, and chlamydia, with gonorrhea and hepatitis C added based on risk factors. Higher-risk patients are retested in the third trimester. Treating an infection before delivery cuts the risk of mother-to-baby HIV transmission to under 1%, prevents nearly all cases of congenital syphilis, and protects against neonatal eye infections, pneumonia, and preterm birth caused by chlamydia and gonorrhea.
Why pregnancy does not shield you from STIs
Pregnancy changes a lot in the body, but it does not change exposure risk. If you are sexually active during pregnancy, especially with a new or untreated partner, the same infections that mattered last year still matter now. The CDC reports that rates of chlamydia, gonorrhea, and syphilis have been rising in pregnant people in the U.S., with congenital syphilis cases reaching record highs in recent surveillance years.
Many STIs are also silent. Up to 70% of women with chlamydia have no obvious symptoms, per CDC screening guidance. Syphilis can cycle through stages where there is no rash, no fever, and no clear sign anything is wrong. Herpes can stay dormant for months and then reactivate under the hormonal and immune shifts of pregnancy. Feeling fine is not the same as being clear, which is why screening is built into routine prenatal care rather than triggered by symptoms.
U.S. cases of congenital syphilis have risen sharply over the past decade. Per <a href="https://www.cdc.gov/syphilis/about/about-congenital-syphilis.html">CDC surveillance</a>, nearly 4,000 cases were reported in 2024, the highest number reported in a single year since 1994, with case counts more than tripling in recent years. Early prenatal syphilis screening combined with a course of benzathine penicillin G can prevent congenital infection when treatment is completed before delivery.
The STIs that matter most before and during pregnancy
Not every infection carries the same risk to a developing baby. The list below covers the ones that come up most often in CDC and ACOG screening guidance, what they can do during pregnancy, and what treatment looks like.
Chlamydia and gonorrhea. Bacterial infections that often have no symptoms in women. Untreated, they can scar the fallopian tubes (causing pelvic inflammatory disease, or PID) and damage fertility before pregnancy. During pregnancy, they raise the risk of preterm rupture of membranes, premature birth, low birth weight, and newborn eye infections (ophthalmia neonatorum) or pneumonia transmitted during vaginal delivery. Both are treatable with antibiotics that are safe in pregnancy.
Syphilis. A bacterial infection that can cross the placenta as early as the second trimester. Untreated maternal syphilis causes miscarriage, stillbirth, neonatal death, or congenital syphilis with bone deformities, blindness, deafness, and neurologic damage. Missed or late screening is the single biggest driver of rising case counts. A simple blood test plus benzathine penicillin G during pregnancy (administered at least 30 days before delivery) is highly effective at preventing congenital infection.
HIV. Without treatment, HIV can transmit during pregnancy, delivery, or breastfeeding. With current antiretroviral therapy taken consistently, that risk falls to less than 1 percent per NIH HIVinfo guidance. HIV-positive parents can and do have HIV-negative babies; the medication and the timing of when it starts are what make the difference.
Hepatitis B and hepatitis C. Both can pass to the baby at delivery. Hepatitis B vertical transmission is largely preventable with maternal antiviral therapy in late pregnancy when viral loads are high, plus hepatitis B vaccine and immunoglobulin given to the newborn within hours of birth. Hepatitis C transmission is lower (around 5 to 6 percent without treatment) and there is no vaccine, but newer direct-acting antivirals can clear hepatitis C in most adults; treatment is generally deferred until after pregnancy.
Genital herpes (HSV-1 and HSV-2). Recurrent outbreaks during pregnancy carry low transmission risk, but a primary (first-ever) infection acquired in the third trimester is dangerous. The mother has not yet developed antibodies that cross to the baby, so neonatal herpes risk at delivery is significantly higher. Antiviral suppression with acyclovir or valacyclovir from around 36 weeks reduces lesion frequency at delivery, and active genital lesions at the time of labor are an indication for cesarean delivery.
Trichomoniasis. A parasitic infection linked with preterm rupture of membranes and low birth weight. It is the most common cause of itching and yellow-green frothy discharge in pregnancy that gets mistaken for a yeast infection. Treatable with metronidazole.
HPV. Most genital HPV infections do not directly affect pregnancy, but high-risk types can change cervical screening management. Routine vaccination is recommended through age 26, with shared clinical decision-making available through age 45 per ACIP guidance.
| STI | Main pregnancy or neonatal risk | Pregnancy-safe treatment |
|---|---|---|
| Chlamydia | Preterm birth, neonatal eye infection, pneumonia | Azithromycin (single dose) or amoxicillin |
| Gonorrhea | Preterm birth, neonatal eye infection | Ceftriaxone intramuscular |
| Syphilis | Miscarriage, stillbirth, congenital syphilis | Benzathine penicillin G (≥30 days before delivery) |
| HIV | Mother-to-child transmission in pregnancy, delivery, or breastfeeding | Combination antiretroviral therapy |
| Hepatitis B | Vertical transmission at birth | Maternal antiviral late in pregnancy + newborn vaccine and HBIG |
| Genital herpes | Neonatal herpes, especially with primary infection late in pregnancy | Acyclovir or valacyclovir suppression from ~36 weeks; cesarean if active lesions at labor |
| Trichomoniasis | Preterm rupture of membranes, low birth weight | Metronidazole (after first trimester) |
When pregnancy symptoms are not really pregnancy symptoms
A lot happens in the genital area during pregnancy. Discharge increases as estrogen and blood flow rise. Skin stretches. Tissues become more sensitive. Persistent itching, burning, color changes, foul smell, or visible sores are different. Those are signals worth checking, not waving off as hormones.
Use this rough guide to tell normal apart from worth-investigating:
- Normal pregnancy discharge (leukorrhea): thin, milky white, with a mild or neutral smell. Increases gradually through pregnancy.
- Trichomoniasis: yellow-green, often frothy, with a strong unpleasant odor and intense itching.
- Bacterial vaginosis (frequently coexists with chlamydia): thin gray discharge with a strong fishy smell, especially after sex.
- Gonorrhea or chlamydia: sometimes thick, sometimes yellow, sometimes accompanied by burning during urination or spotting; often has no symptom at all.
- Genital herpes: tingling, itching, or burning followed by clusters of small painful blisters or shallow ulcers.
- HPV-related warts: painless flesh-colored bumps around the vulva, anus, or cervix.
If you are itching and over-the-counter yeast treatment is not helping in a few days, that is a strong reason to test rather than retreat. Yeast and trichomoniasis can look similar from the outside but require completely different medication, and trich raises preterm-birth risk if it is left to grow.
| Likely cause | Discharge appearance | Itching or burning | Odor |
|---|---|---|---|
| Normal pregnancy (leukorrhea) | Thin, milky white | Usually none | Mild or neutral |
| Yeast infection | Thick white, cottage-cheese-like | Intense itching, often burning | Mild or yeasty |
| Trichomoniasis | Yellow-green, often frothy | Intense itching | Strong, unpleasant |
| Bacterial vaginosis | Thin gray | Mild or none | Strong fishy, especially after sex |
| Chlamydia or gonorrhea | Thick or yellow when present; often none | Burning during urination | Variable; often none |
| Genital herpes (outbreak) | Usually none; clear blister fluid possible | Tingling then sharp pain | Usually none |
Testing before you try to conceive
Preconception screening sits in the same category as folic acid and vaccine boosters: a few small tasks that do a lot of work. Knowing your status before pregnancy gives you and your provider time to treat any infection, retest for cure, and make sure both partners are clear before conception. It also surfaces fertility-relevant findings (like prior PID from undetected chlamydia) before you spend months wondering why conception is not happening.
A reasonable preconception checklist:
- Screen at least 3 months before trying to conceive, so there is time for treatment, retesting, and clearance.
- Test together with your partner, not just yourself. Reinfection from an untreated partner is one of the most common reasons chlamydia or gonorrhea recurs.
- Catch up on adult vaccines (hepatitis B, HPV if eligible, MMR, varicella) per current ACIP guidance.
- Disclose any past STIs to your OB-GYN, even cleared ones; previous chlamydia or gonorrhea matters for fertility evaluation.
At-home rapid tests can shorten the time from suspicion to clarity, especially when clinic access is limited. They are lateral-flow chemistry, useful for screening, and a positive result is worth confirming with a clinic so treatment can be prescribed and dosed correctly. A negative result during a window period is not the same as cleared infection, so timing relative to exposure matters.
The three-month buffer covers two things people commonly skip: completing a full antibiotic course (most regimens for chlamydia or gonorrhea are single-dose or one-week, but reinfection from an untreated partner can stretch the cycle out), and a test of cure to confirm the infection actually cleared. Conceiving with active untreated bacterial STI raises miscarriage and preterm-birth risk, while conceiving immediately after one round of treatment without retesting carries similar risk if the partner reinfects you. Three months gives both partners time to test, treat, and reconfirm before trying.
What prenatal STI screening actually looks like
Most OB-GYNs run a panel at the first prenatal visit. Per CDC guidance, that universal panel covers HIV, syphilis, hepatitis B, and chlamydia, with gonorrhea added for patients under 25 or with risk factors, and hepatitis C added universally in many U.S. settings. Sample collection is straightforward and safe in pregnancy: a blood draw for HIV, syphilis, and hepatitis serology; a urine sample or vaginal swab for chlamydia and gonorrhea NAAT testing.
One catch worth knowing about: that first-visit panel is often a one-time test unless your OB orders a retest. New exposure later in pregnancy will not show up unless you ask for it. ACOG specifically recommends repeat third-trimester screening for syphilis, HIV, and gonorrhea/chlamydia in patients with ongoing risk factors or in geographic areas with high syphilis rates.
Clinic chlamydia and gonorrhea testing uses NAAT (nucleic acid amplification testing), the lab gold standard for analytical sensitivity. At-home rapid kits use lateral-flow chemistry, which trades a small amount of sensitivity for speed and privacy. They work best as screening alongside, not in place of, prenatal-care testing. A negative home result with ongoing symptoms is still worth a clinic confirmation.
Treating STIs safely during pregnancy
Most STIs that show up in pregnancy are treatable, and the medications used are chosen for compatibility with fetal development. A short summary of standard regimens per CDC STI treatment guidelines:
- Syphilis: benzathine penicillin G. Penicillin is the only treatment proven to prevent congenital syphilis. Penicillin allergy in pregnancy is managed by desensitization rather than substitution.
- Chlamydia: azithromycin (single dose) or amoxicillin. Doxycycline is avoided in pregnancy.
- Gonorrhea: ceftriaxone intramuscular injection.
- Trichomoniasis: metronidazole, considered safe in pregnancy after the first trimester per current CDC guidance.
- HIV: combination antiretroviral therapy throughout pregnancy, intrapartum, and for the newborn after delivery; regimen choice depends on prior treatment history and resistance profile.
- Hepatitis B: tenofovir in late pregnancy for high viral loads, plus newborn vaccine and HBIG within 12 hours of birth.
- Genital herpes: acyclovir or valacyclovir suppression starting around 36 weeks for patients with a history of outbreaks; cesarean delivery if active genital lesions are present at labor.
The pattern across all of these: treatment works, and it works best when there is time. Late-trimester diagnosis still helps a lot, but earlier is better.
The fertility angle: STIs and PID
If pregnancy is the goal but it is not happening, untreated STIs are worth ruling out before deeper fertility workup. Chlamydia and gonorrhea are the leading infectious causes of female-factor infertility globally. The mechanism is pelvic inflammatory disease: bacteria ascend from the cervix into the uterus and fallopian tubes, trigger inflammation, and leave scar tissue behind. Scarred tubes block egg-and-sperm meeting, raise the risk of ectopic pregnancy when conception does happen, and create chronic pelvic pain.
Damage is often done before any symptoms appear. By the time someone notices pelvic pain or trouble conceiving, the structural changes can be permanent. Each repeat chlamydia infection raises the risk of tubal-factor infertility further, which is why test-and-retest after treatment matters as much as initial screening.
Other long-term risks of unaddressed STIs include:
- Ectopic pregnancy, where a fertilized egg implants outside the uterus; a medical emergency.
- Chronic pelvic inflammation that can persist after the original infection has been cleared.
- Higher risk of miscarriage in subsequent pregnancies if intrauterine inflammation has changed the endometrial environment.
Chlamydia-driven pelvic inflammatory disease is a leading infectious cause of female-factor infertility worldwide. Each repeat infection compounds tubal-factor risk, and once fallopian-tube scarring forms it can be permanent. Most women with chlamydia have no symptoms, so the damage often happens before there is any reason to suspect it. Screening and treatment before trying to conceive is the most reliable prevention.
What to do if you test positive while pregnant
A positive STI test during pregnancy is not a verdict on you or on the pregnancy. It is information you now have time to act on. The order of operations:
- Confirm with your OB-GYN. Bring the at-home result or clinic report. They will run a confirmatory test where indicated and prescribe pregnancy-safe treatment.
- Start treatment as prescribed. Complete the full course even if symptoms improve sooner; partial treatment is the most common reason an infection persists or comes back.
- Notify partners. Reinfection from an untreated partner is the most common reason a treated infection recurs. Many clinics can help with partner notification if that conversation is hard.
- Schedule a test of cure. Especially for chlamydia, gonorrhea, and trichomoniasis. CDC currently recommends repeat testing roughly 3 weeks after treatment in pregnancy, plus an additional retest 3 months after treatment to catch reinfection.
- Coordinate delivery planning if relevant. Active genital herpes lesions at term, high HIV viral load, or untreated syphilis affect labor and delivery decisions; your OB will work this through with you.
Millions of pregnancies per year include an STI diagnosis somewhere along the way and end with healthy babies when screening, treatment, and retesting happen in time.
Maternal syphilis treated with benzathine penicillin G at least 30 days before delivery prevents the great majority of congenital syphilis cases per CDC guidance. HIV viral suppression with consistent antiretroviral therapy reduces mother-to-child transmission to under 1% per NIH HIVinfo. Hepatitis B vaccine plus immunoglobulin given to the newborn within 12 hours of birth blocks most vertical transmission. Each of these interventions depends on the diagnosis being made early enough to act on.
Why retesting in the third trimester matters
One negative test in the first trimester is reassurance for that point in time, not for the rest of pregnancy. Risk profiles can change across nine months: a new partner, a partner who tested positive, fresh symptoms, or living in a high-prevalence area can all reset the clock on screening. ACOG specifically recommends repeat third-trimester screening for several patient groups.
The third-trimester window also drives antiviral suppression decisions for genital herpes. If a primary genital herpes outbreak happens late in pregnancy, the highest-risk scenario, knowing about it before labor starts is what allows for cesarean planning and reduces neonatal herpes risk.
Prevention basics that actually work
Prevention during pregnancy is not very different from prevention outside of it. The few habits that have the most evidence behind them:
- Condom use during pregnancy reduces exposure to HIV, syphilis, gonorrhea, chlamydia, trichomoniasis, and hepatitis B from a partner whose status is unknown or known positive. Skin-to-skin infections (herpes, HPV) are partially but not fully blocked.
- Mutual screening with partners before unprotected sex, especially in new relationships, catches asymptomatic carriers.
- Hepatitis B and HPV vaccination are routine adult interventions per ACIP. Hepatitis B is given to all newborns at birth; HPV is recommended through age 26 with shared decision-making to age 45.
- Open conversation with your provider about your sexual history (partners, recent exposures, prior STIs) shapes which tests are ordered and when retesting happens.
A pregnant person who has an STI may pass the infection to their baby before, during, or after birth. Prenatal screening and treatment can prevent or reduce these risks for the baby and the pregnant person.
FAQs
- Can STIs really affect my ability to get pregnant?
- Yes. Untreated chlamydia and gonorrhea are the most common infectious causes of female-factor infertility worldwide because they trigger pelvic inflammatory disease, which scars the fallopian tubes. Each repeat infection raises the risk further. Screening and treating before trying to conceive prevents most of this.
- Which STIs are most dangerous during pregnancy?
- Syphilis, HIV, herpes acquired in the third trimester, hepatitis B, chlamydia, and gonorrhea carry the highest risk to the baby. All are screenable. All except primary herpes acquired late are highly treatable during pregnancy.
- Is STI testing part of routine prenatal care?
- Yes. CDC and ACOG recommend universal first-prenatal-visit screening for HIV, syphilis, hepatitis B, and chlamydia, with gonorrhea and hepatitis C added based on risk factors and local prevalence. Third-trimester retesting is recommended for higher-risk patients.
- Can I be treated for an STI safely while pregnant?
- Yes. Penicillin clears syphilis; azithromycin or amoxicillin clears chlamydia; ceftriaxone clears gonorrhea; metronidazole clears trichomoniasis after the first trimester. HIV is managed with antiretroviral therapy throughout pregnancy. All of these are chosen specifically for safety in pregnancy.
- If my first prenatal screen was negative, do I need to test again later?
- Sometimes yes. If your risk has changed (new partner, new symptoms, partner diagnosed), or if you live in an area with high syphilis or HIV rates, ACOG recommends repeat screening in the third trimester. A test from week 10 does not protect against an exposure at week 28.
- Can a baby get an STI from the mother?
- Yes, depending on the infection. Syphilis crosses the placenta. HIV can transmit during pregnancy, delivery, or breastfeeding. Hepatitis B and herpes typically transmit at delivery. Chlamydia and gonorrhea transmit through the birth canal. Treatment dramatically reduces or eliminates each of these risks.
- Is vaginal itching during pregnancy always hormonal?
- Often yes, but not always. Persistent itching paired with unusual discharge, odor, burning, or sores is worth testing. Trichomoniasis in particular causes itching that gets mistaken for a yeast infection but raises preterm-birth risk and needs different treatment.
- Where can I order a discreet at-home STI test during pregnancy?
- Rapid lateral-flow home kits cover the most common STIs and deliver results in roughly 15 minutes. They are useful for screening alongside prenatal care, not as a replacement. Confirm any positive result with your OB-GYN. For comprehensive preconception or pregnancy-context screening, see the <a href="https://www.stdrapidtestkits.com/the-10-most-common-std-complete-at-home-self-test-kit-for-women">10-in-1 women's panel</a> or the <a href="https://www.stdrapidtestkits.com/chlamydia-gonorrhea-syphilis-home-test-kit">3-in-1 chlamydia/gonorrhea/syphilis kit</a>.
- U.S. Centers for Disease Control and Prevention. Sexually transmitted infection treatment guidelines, including pregnancy-specific recommendations for syphilis, chlamydia, gonorrhea, herpes, and trichomoniasis, plus third-trimester retesting guidance.
- U.S. Centers for Disease Control and Prevention. Congenital syphilis surveillance data and trend reporting for U.S. case counts, including 2024 figures.
- World Health Organization. Sexually transmitted infections (STIs) global fact sheet covering prevalence, transmission, and pregnancy outcomes.
- U.K. National Health Service. Sexually transmitted infections overview, symptoms, testing, and treatment guidance.
- American College of Obstetricians and Gynecologists. Pregnancy-related clinical guidance, including third-trimester STI retesting recommendations.
- U.S. National Institutes of Health, HIVinfo. Preventing perinatal transmission of HIV during pregnancy and childbirth, including antiretroviral therapy and the under-1% transmission risk on consistent treatment.