The STIs That Matter Most in Pregnancy

Which STIs matter most in pregnancy

The STIs that matter most in pregnancy are the ones that can pass to the baby: syphilis, HIV, and hepatitis B before or around birth; herpes at delivery; and chlamydia and gonorrhea, which can affect a newborn. Because most cause no symptoms in the mother, they are found by screening rather than by how she feels.

This is exactly why guidelines fold an STI panel into routine prenatal care. Standard recommendations call for testing every pregnant woman for syphilis, HIV, and hepatitis B, and for screening younger or higher-risk women for chlamydia and gonorrhea as well 1Ref 1Centers for Disease Control and Prevention (2021).STI Screening Recommendations.CDC population-specific STI screening recommendations, including screening every pregnant woman for syphilis, HIV, and hepatitis, and screening younger or higher-risk pregnant women for chlamydia and gonorrhea.. The tests are ordinary blood draws and a urine sample, usually taken at the first prenatal visit alongside everything else. None of them is a judgment; they are as routine as checking a blood type or a blood pressure.

In pregnancy, screening is not about suspicion — it is a standard step that lets a treatable infection be handled before it can reach the baby.

The prenatal STI panel most women can expect looks like this:

Understanding this prenatal sti screening panel is the backbone of everything that follows.

Syphilis: the one that can be passed before birth

Syphilis is the infection that makes universal prenatal screening non-negotiable, because it can cross the placenta and infect the fetus directly — a condition called congenital syphilis. Untreated, it can cause miscarriage, stillbirth, a baby born too early, or severe, lasting damage to a newborn's bones, brain, and organs 2Ref 2Centers for Disease Control and Prevention (2024).About Congenital Syphilis.Syphilis can pass to a fetus during pregnancy causing congenital syphilis, with outcomes including stillbirth and severe damage, and penicillin during pregnancy is the only effective treatment to prevent it.. It is also one of the most preventable of these outcomes.

What makes syphilis both dangerous and manageable is that it responds to a single, well-established treatment. Penicillin given during pregnancy is the only therapy proven to treat the mother and prevent the infection from reaching the baby, and it works best the earlier in pregnancy it is given 2Ref 2Centers for Disease Control and Prevention (2024).About Congenital Syphilis.Syphilis can pass to a fetus during pregnancy causing congenital syphilis, with outcomes including stillbirth and severe damage, and penicillin during pregnancy is the only effective treatment to prevent it.. That is why a positive syphilis test at any point in pregnancy is treated promptly rather than watched, and it is the reasoning behind screening for it more than once. For many parents, this is the reassuring part of an otherwise frightening diagnosis: the treatment is old, well understood, and reliable, and it works.

Because a woman can acquire syphilis after her first prenatal test, many providers screen again later in pregnancy and at delivery, particularly where local rates are high. Syphilis is also one of the reportable STIs, meaning a diagnosis is shared with the health department so partners can be reached and the baby monitored — part of a public-health effort to bring congenital syphilis back down. The takeaway is simple: found and treated in time, syphilis in pregnancy is almost entirely preventable in the baby.

Chlamydia and gonorrhea: silent, common, and treatable

Chlamydia and gonorrhea are the most common bacterial STIs in pregnancy, and like elsewhere they are usually silent 3Ref 3Centers for Disease Control and Prevention (2024).About Chlamydia.Chlamydia is a common, frequently asymptomatic bacterial STI that is curable with antibiotics.. In pregnancy the concern is twofold: both can affect the pregnancy itself, and both can pass to the baby during delivery, where they can cause a newborn eye infection. Both are also curable during pregnancy with antibiotics chosen for their safety record 3Ref 3Centers for Disease Control and Prevention (2024).About Chlamydia.Chlamydia is a common, frequently asymptomatic bacterial STI that is curable with antibiotics..

Timing of treatment is a common worry — many women fear that any antibiotic could harm the baby — but the antibiotics used for chlamydia and gonorrhea in pregnancy are chosen precisely because they have a long record of safe use, and leaving the infection untreated carries the greater risk. Screening is recommended at the first prenatal visit for women under 25 and for older women with risk factors such as a new or additional partner, and repeated later when risk continues 1Ref 1Centers for Disease Control and Prevention (2021).STI Screening Recommendations.CDC population-specific STI screening recommendations, including screening every pregnant woman for syphilis, HIV, and hepatitis, and screening younger or higher-risk pregnant women for chlamydia and gonorrhea.. Because reinfection undoes treatment, a partner's treatment is part of the plan, not an afterthought.

The risks, the screening, and the safe treatment window for one of these are covered in a dedicated guide on chlamydia in pregnancy. The short version is reassuring: caught on a routine prenatal test, chlamydia and gonorrhea are among the easiest of the pregnancy STIs to treat, and treating them removes most of the risk they carry.

Hepatitis B and hepatitis C in pregnancy

Hepatitis B and hepatitis C are bloodborne infections that can be sexually transmitted, and both can pass from mother to baby — which is why both are now part of prenatal screening. Hepatitis B is checked at the first visit in every pregnancy, because it can be transmitted to a baby around the time of birth, and knowing a mother carries it lets a newborn be protected right after delivery 4Ref 4Centers for Disease Control and Prevention (2024).Clinical Overview of Hepatitis B.Hepatitis B transmission routes include perinatal (mother-to-child around the time of birth), which is why it is part of prenatal screening..

Hepatitis C screening has broadened: current recommendations call for testing all adults at least once, and that now includes during pregnancy 5Ref 5US Preventive Services Task Force (2020).Hepatitis C Virus Infection in Adolescents and Adults: Screening.The 2020 USPSTF Grade B recommendation to screen all adults aged 18 to 79 for hepatitis C, which includes screening during pregnancy.. A mother who tests positive does not usually pass it, but knowing her status means her baby can be followed and tested rather than missed. For the mother, learning her hepatitis status also opens the door to her own care after delivery, which she might not otherwise have sought. A hepatitis result, positive or negative, is simply recorded and acted on like any other routine prenatal lab.

A positive hepatitis result in pregnancy is information, not an emergency — its whole value is that it lets a baby be protected or monitored from day one. Neither infection changes the plan for a healthy delivery; both simply need to be known, because the protection they enable only works if the infection is identified before, or right at, birth.

Herpes and delivery

Herpes matters in pregnancy mainly at one moment: delivery. Genital herpes is caused by the herpes simplex virus and cannot be cured, but the risk to a baby is not from the pregnancy itself — it is from contact with an active outbreak during a vaginal birth, which can cause a serious newborn infection 6Ref 6Centers for Disease Control and Prevention (2024).About Genital Herpes.Genital herpes is caused by HSV, has no cure but is managed with antivirals including suppressive therapy to reduce transmission, and can be transmitted even without visible symptoms.. The good news is that this risk is both uncommon and manageable.

Two things lower it. Antiviral medicine, which can be taken later in pregnancy, reduces outbreaks and the amount of virus present around the due date 6Ref 6Centers for Disease Control and Prevention (2024).About Genital Herpes.Genital herpes is caused by HSV, has no cure but is managed with antivirals including suppressive therapy to reduce transmission, and can be transmitted even without visible symptoms.. And if there is an active sore or warning symptoms when labor begins, a cesarean delivery avoids the birth-canal contact that carries the risk. Because herpes can be transmitted even without a visible sore, honesty about a herpes history — including a partner's — lets a provider plan for it well before labor.

The nuances of timing, testing, and delivery choices are covered in a dedicated guide on herpes in pregnancy. For most women with herpes, a plan set before labor means the overwhelming likelihood is a healthy vaginal birth and a healthy baby.

HIV in pregnancy

HIV in pregnancy is the clearest example of how much has changed. Every pregnant woman is recommended to be tested early, because HIV that is known and treated behaves completely differently from HIV that is not 1Ref 1Centers for Disease Control and Prevention (2021).STI Screening Recommendations.CDC population-specific STI screening recommendations, including screening every pregnant woman for syphilis, HIV, and hepatitis, and screening younger or higher-risk pregnant women for chlamydia and gonorrhea.. With treatment that keeps the virus suppressed, the chance of passing HIV to the baby drops to a very low level, and a healthy pregnancy and birth become the expected outcome rather than the exception.

The practical implications follow from testing early. A woman who already knows her status stays on or starts treatment; a woman who tests positive during pregnancy begins treatment and is supported through it; and where there is ongoing exposure risk, prevention options exist to keep an HIV-negative mother negative. What ties it together is that none of it can happen without the test.

The difference between an HIV diagnosis a generation ago and one today, in the context of pregnancy, is the difference between a feared outcome and a managed one. This is why HIV screening is offered to every pregnant woman, not only those who consider themselves at risk: the infection is not something a mother can feel, and the interventions that protect a baby all depend on knowing early. That early test is also the start of a mother's own long-term care, not only her baby's protection. A separate guide covers what an HIV diagnosis means today in full.

What screening and prevention look like across a pregnancy

Across a pregnancy, STI care follows a simple rhythm: screen early, treat what is found, and re-screen when risk continues. The first prenatal visit carries the main panel — syphilis, HIV, hepatitis B, hepatitis C, and, for many, chlamydia and gonorrhea — and for higher-risk pregnancies, syphilis and the others may be repeated in the third trimester and at delivery 1Ref 1Centers for Disease Control and Prevention (2021).STI Screening Recommendations.CDC population-specific STI screening recommendations, including screening every pregnant woman for syphilis, HIV, and hepatitis, and screening younger or higher-risk pregnant women for chlamydia and gonorrhea.. Most STIs cause no symptoms, so this schedule, not a set of warning signs, is what catches them.

Prevention during pregnancy is the same as outside it, with higher stakes. Consistent condom use lowers the risk of picking up a new STI, and it is worth continuing through pregnancy, especially with a new or non-monogamous partner. A new partner during pregnancy is itself a reason to retest, since an infection acquired after the first-visit panel is exactly what a third-trimester screen is designed to catch. For anyone planning a pregnancy, testing before conception is even simpler than testing during it, and it removes the question entirely.

If a test comes back positive, the response is treatment, not alarm: nearly every STI on the prenatal panel can be treated or managed in ways that protect the baby, and the reportable ones bring in a health department that helps reach partners. The message running through this whole hub is that the risks these infections carry in pregnancy are, in almost every case, the risks of an infection that went unfound — which is precisely what prenatal screening exists to prevent.