Infections in Pregnancy and How They Affect the Baby

Pregnancy is a beautiful biological project: one tiny roommate, one very busy body, and approximately 4,000 things people suddenly tell you not to eat. Somewhere between prenatal vitamins and the great deli-meat debate sits a serious topic that deserves clear, calm attention: infections in pregnancy.

The good news is that most infections during pregnancy do not cause major problems for the baby. A basic cold, a small skin infection, or a short-lived stomach bug often passes without drama. The less fun news is that certain bacteria, viruses, and parasites can affect pregnancy, fetal development, birth timing, or newborn health. Some can cross the placenta. Some can spread during labor and delivery. Others can make the pregnant person seriously ill, which indirectly affects the baby by increasing the risk of complications such as preterm birth or low birth weight.

This guide explains the most important infections in pregnancy, how they may affect the baby, warning signs to take seriously, and practical prevention steps. No panic, no doom scrolling, no “one grape touched soft cheese, is everything over?” energy. Just useful information, served with a side of common sense.

Why Infections Matter More During Pregnancy

During pregnancy, the immune system changes so the body can support the growing baby. That does not mean pregnant people are fragile glass ornaments. It means some infections may be easier to catch, harder to fight, or more likely to cause complications.

Infections can affect a baby in several ways. Some germs can move through the placenta and infect the fetus directly. Others can inflame the placenta or amniotic fluid, making the uterus a less peaceful place to grow. Some infections trigger fever or inflammation in the pregnant person, which can increase the chance of contractions or early labor. A few infections spread mainly during vaginal birth, when the baby passes through the birth canal.

Timing matters, too. Infection early in pregnancy may interfere with organ development. Infection late in pregnancy may be more likely to pass to the baby, depending on the germ. This is why prenatal screening, vaccines, safe food habits, and early treatment are not “extra credit.” They are the pregnancy version of wearing a seat belt: simple, boring, and incredibly useful.

Common Infections in Pregnancy That Can Affect the Baby

1. Cytomegalovirus (CMV)

Cytomegalovirus, usually called CMV because nobody wants to say “cytomegalovirus” before coffee, is a common virus spread through body fluids such as saliva and urine. Many healthy adults have mild symptoms or none at all. The concern during pregnancy is congenital CMV, which happens when the virus passes to the developing baby.

Congenital CMV can cause hearing loss, vision problems, small head size, seizures, low birth weight, liver or spleen enlargement, and developmental delays. Some babies look healthy at birth but develop hearing loss later, which is why follow-up testing matters when CMV is diagnosed.

Prevention focuses on hygiene, especially around toddlers and young children. Wash hands after changing diapers, wiping noses, or handling toys. Avoid sharing utensils, food, drinks, toothbrushes, or pacifiers with young children. It is not glamorous, but neither is catching a virus from a half-chewed cracker.

2. Listeria

Listeria is a foodborne bacterium that can live in refrigerated foods. Pregnant people are more vulnerable to listeriosis than the average healthy adult, and symptoms may be mild: fever, fatigue, muscle aches, nausea, or diarrhea. Unfortunately, the infection can be much more serious for the baby.

Listeria during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection in the newborn. Foods commonly associated with risk include unpasteurized milk, soft cheeses made with unpasteurized milk, deli meats, refrigerated smoked seafood, and ready-to-eat foods that have not been handled safely.

Helpful habits include heating deli meats until steaming hot, avoiding unpasteurized dairy, washing produce well, keeping the refrigerator cold, separating raw foods from ready-to-eat foods, and cooking meat, poultry, seafood, and eggs thoroughly. Food safety may not sound thrilling, but neither does a bacterium that treats your fridge like a vacation rental.

3. Toxoplasmosis

Toxoplasmosis is caused by the parasite Toxoplasma gondii. It can spread through undercooked meat, contaminated soil, unwashed produce, or cat feces. Cats are not villains; they are just very committed to being mysterious. The real issue is exposure to contaminated litter or soil during pregnancy.

If toxoplasmosis is first acquired during pregnancy, it can pass to the baby. Some infected babies appear normal at birth but later develop eye disease, learning problems, seizures, or developmental delays. In more severe cases, babies may have brain or eye damage at birth.

To reduce risk, cook meat thoroughly, wash fruits and vegetables, wear gloves while gardening, wash hands after handling raw meat, and ask someone else to change the litter box if possible. If that is not possible, use gloves and wash hands afterward. Also, change litter daily because the parasite needs time to become infectious.

4. Group B Strep (GBS)

Group B strep is a type of bacteria that can live in the vagina or rectum without causing symptoms. It is common and usually harmless in adults, but it can cause serious illness in newborns if passed during delivery.

GBS can lead to newborn sepsis, pneumonia, or meningitis, especially in the first week of life. That sounds scary, but this is one of the best examples of how prenatal care prevents problems. Pregnant patients are usually screened for GBS late in pregnancy, and those who test positive receive IV antibiotics during labor to reduce the baby’s risk.

A positive GBS test does not mean the pregnant person did anything wrong, and it does not mean the baby will be sick. It means the care team gets a heads-up and can act before the bacteria has a chance to cause trouble.

5. Syphilis and Other Sexually Transmitted Infections

Some sexually transmitted infections can affect pregnancy and newborn health. Syphilis is especially important because it can pass through the placenta and cause congenital syphilis. Untreated syphilis in pregnancy may lead to miscarriage, stillbirth, premature birth, low birth weight, newborn death, bone problems, blindness, deafness, or developmental delays.

Chlamydia and gonorrhea can spread to the baby during birth and cause newborn eye infections or, in some cases, more serious illness. Genital herpes is usually passed during delivery if active lesions or a new infection are present near birth; neonatal herpes can be severe and may affect the brain, eyes, skin, or organs.

HIV can pass during pregnancy, birth, or breastfeeding, but early testing and consistent antiretroviral treatment greatly reduce the chance of transmission. Hepatitis B can also pass from parent to baby; newborn vaccination and hepatitis B immune globulin for exposed infants are key prevention tools.

The practical takeaway is simple: prenatal STI screening is not about judgment. It is about catching treatable infections early. Medicine cannot help with what it does not know about, so testing is a power move.

6. Rubella, Chickenpox, Parvovirus B19, and Zika

Rubella infection during pregnancy, especially early pregnancy, can cause miscarriage, stillbirth, or congenital rubella syndrome. Babies with congenital rubella syndrome may have hearing loss, heart defects, cataracts, developmental delays, or other lifelong complications. The MMR vaccine protects against rubella, but it is not given during pregnancy, so immunity is best checked before conception or addressed after delivery.

Chickenpox, caused by varicella-zoster virus, can be serious for pregnant people and newborns. If infection occurs around delivery, the newborn may be at risk for neonatal varicella. If infection happens earlier in pregnancy, rare congenital complications may occur. People who are not immune should call their healthcare provider promptly after exposure.

Parvovirus B19, also known as fifth disease, usually causes a mild rash illness in children, but infection during pregnancy can sometimes pass to the fetus. In rare cases, it may cause severe fetal anemia, hydrops, miscarriage, or other complications, especially when infection occurs in the first half of pregnancy.

Zika virus infection during pregnancy can cause serious brain and eye birth defects, including microcephaly. Zika is spread mainly by mosquitoes and can also be sexually transmitted. Pregnant people or those planning pregnancy should check travel guidance before visiting areas with Zika risk and take mosquito-bite prevention seriously.

7. Flu, COVID-19, and RSV

Respiratory infections can be more than “just a bad cold” during pregnancy. Flu is more likely to cause severe illness and hospitalization in pregnant people, and high fever or severe illness can affect pregnancy. COVID-19 during pregnancy has been linked with increased risk of severe maternal illness and complications such as preterm birth. RSV is especially important for newborns because infants can become very sick from it in the first months of life.

Vaccination during pregnancy helps protect both the pregnant person and the baby. Flu vaccination can be given during any trimester. COVID-19 vaccination has been shown to help protect pregnant people and may pass protective antibodies to the baby. Maternal RSV vaccination during the recommended pregnancy window can help protect infants after birth. Tdap vaccination during each pregnancy also protects newborns from pertussis, better known as whooping cough.

Think of maternal vaccines as sending the baby to the outside world with a tiny immune-system welcome basket.

8. Urinary Tract Infections and Bacterial Vaginosis

Urinary tract infections are common during pregnancy. When treated early, they often resolve without major issues. Untreated UTIs can move to the kidneys and may be associated with preterm birth or low birth weight. Symptoms may include burning while urinating, frequent urination, pelvic discomfort, fever, chills, back pain, or urine that smells unusual.

Bacterial vaginosis, or BV, happens when the usual balance of vaginal bacteria changes. BV may cause thin discharge, odor, itching, or burning, though some people have no symptoms. During pregnancy, BV has been associated with premature birth and low birth weight. Symptomatic BV should be discussed with a healthcare provider because treatment is available.

How Infections Can Affect the Baby

Not every infection harms the baby, and even infections known to carry risk do not always cause complications. Still, the possible effects include:

• Miscarriage or stillbirth: Certain infections can affect the placenta, fetus, or pregnancy environment severely enough to cause pregnancy loss.
• Preterm birth: Infection and inflammation can trigger early labor or lead doctors to recommend early delivery for safety.
• Low birth weight: Infection may affect fetal growth or cause early delivery before the baby has had enough time to gain weight.
• Birth defects: Rubella, CMV, Zika, toxoplasmosis, and some other infections can affect the brain, eyes, ears, heart, or other organs.
• Newborn infection: GBS, herpes, gonorrhea, chlamydia, hepatitis B, HIV, and other infections may affect the baby during birth or shortly after.
• Long-term developmental issues: Hearing loss, vision problems, seizures, learning delays, or motor challenges can occur after some congenital infections.

The key phrase is “can occur,” not “will occur.” Prenatal care, testing, treatment, vaccination, and safe habits dramatically reduce risk.

Warning Signs: When to Call a Healthcare Provider

Pregnancy comes with enough weird symptoms to make anyone wonder whether their body has installed experimental software. Still, some signs deserve a call to a healthcare provider right away:

• Fever of 100.4°F or higher
• Flu-like symptoms, especially after eating high-risk foods
• Burning or pain with urination
• Severe headache, stiff neck, rash, or confusion
• New genital sores, blisters, or unusual discharge
• Exposure to chickenpox, rubella, parvovirus B19, or Zika
• Decreased fetal movement after the baby’s movement pattern is established
• Persistent vomiting, dehydration, chills, or back pain
• Any symptom that feels intense, unusual, or frightening

Calling is not “being dramatic.” It is using the medical team exactly as intended. Obstetric offices hear questions all day. You will not win a trophy for silently worrying at 2 a.m.

How to Prevent Infections During Pregnancy

Keep Prenatal Appointments

Prenatal care includes screening for infections that may not cause symptoms. These may include HIV, hepatitis B, hepatitis C, syphilis, chlamydia, gonorrhea, urine infections, and GBS. Screening schedules vary by risk factors, state requirements, and healthcare practice, so follow your provider’s plan.

Stay Current on Recommended Vaccines

Vaccines recommended during pregnancy may include flu, Tdap, COVID-19, and RSV, depending on timing and individual circumstances. Some vaccines, such as MMR and varicella, are not given during pregnancy but may be recommended before pregnancy or after delivery if you are not immune.

Practice Smart Food Safety

Wash hands, cutting boards, and produce. Cook meat and seafood thoroughly. Avoid unpasteurized milk and cheeses. Heat leftovers until steaming. Keep cold foods cold and hot foods hot. When in doubt, throw it out. Your refrigerator is not a courtroom; suspicious leftovers do not need a fair trial.

Use Gloves for Soil, Gardening, and Litter

Soil and cat litter can carry toxoplasmosis. Wear gloves when gardening or handling litter, wash hands well afterward, and avoid changing litter when someone else can do it. This is one chore pregnancy can absolutely delegate.

Reduce Exposure to Saliva and Urine from Young Children

CMV often spreads through young children. Wash hands after diaper changes, do not share utensils or cups, and clean toys and surfaces. Loving a toddler does not require finishing their applesauce.

Practice Safer Sex

Use condoms if STI exposure is possible, make sure partners are tested, and tell your provider about new partners or symptoms. STI testing is routine healthcare, not a character review.

Ask Before Traveling

Before international or mosquito-heavy travel, ask about Zika, malaria, dengue, and other infection risks. Use EPA-registered insect repellent approved for pregnancy, wear long sleeves when practical, and stay in places with screens or air conditioning.

Treatment: What Happens If You Do Get an Infection?

Treatment depends on the infection, pregnancy stage, symptoms, and test results. Many bacterial infections can be treated safely with antibiotics during pregnancy. Antiviral medicines may be used for flu, herpes, HIV, hepatitis B, or other viral infections when appropriate. Some infections require extra ultrasounds, fetal monitoring, specialist care, or newborn testing after delivery.

The most important rule is not to self-treat with leftover antibiotics, herbal remedies, or internet-famous “immune boosters.” Pregnancy is not the season for mystery potions. Always ask a healthcare provider before taking medication, supplements, or alternative remedies.

Real-Life Experience Notes: What This Looks Like in Everyday Pregnancy

In real life, infections in pregnancy are rarely as neat as a textbook chart. They show up while someone is trying to work, care for older children, cook dinner, and remember whether the prenatal appointment is Tuesday or Wednesday. A pregnant person may feel fine one morning, then develop chills by evening and wonder whether it is a harmless bug or something worth calling about. The uncertainty is often the hardest part.

One common experience is the “food panic.” Someone eats a turkey sandwich before remembering that deli meat can carry listeria risk. Cue the mental courtroom: Was it heated? Was it fresh? Did it smell weird? Should I call? In most cases, one sandwich does not equal disaster, but symptoms such as fever, muscle aches, diarrhea, or flu-like illness after a risky food exposure should be discussed with a provider. The lesson is not to live in fear of lunch; it is to build safer habits going forward.

Another familiar situation is daycare exposure. A parent may hear that a child’s class has fifth disease, hand-foot-and-mouth disease, flu, or chickenpox. Suddenly, a cheerful preschool newsletter feels like a tiny public-health thunderstorm. The best move is to call the obstetric provider, explain the exposure, and ask whether testing or monitoring is needed. Many adults are already immune to infections like parvovirus B19 or chickenpox, but guessing is less helpful than checking.

Then there is the awkwardness of STI testing. Some people feel embarrassed when a provider recommends repeat screening for syphilis, HIV, chlamydia, or gonorrhea. But these tests are normal parts of prenatal safety. A positive result is not a moral failure. It is information. And in pregnancy, information can prevent blindness, pneumonia, liver disease, newborn infection, or pregnancy loss. That is not awkward; that is powerful.

GBS screening is another classic example. Many patients feel alarmed when they test positive, but GBS is common. It does not mean poor hygiene, risky behavior, or that the baby is destined for illness. It simply tells the labor team to give antibiotics during labor. In other words, the test turns an invisible risk into a manageable plan.

Parents also describe feeling overwhelmed by vaccine decisions. Flu, Tdap, COVID-19, RSVthe list can sound like alphabet soup. But maternal vaccination has a clear purpose: it protects the pregnant person and passes antibodies to the baby, especially during the early months when newborns are too young for certain vaccines. A good provider can explain timing, benefits, and individual considerations without pressure or judgment.

The emotional experience matters, too. Pregnancy already comes with heightened responsibility. Add infection warnings, and it is easy to feel as if danger is hiding in every salad, sandbox, sneeze, and shopping cart handle. That is not the goal. The goal is confidence: wash your hands, keep food safe, attend prenatal visits, get recommended tests, take symptoms seriously, and call when unsure. You do not need to control every germ on Earth. You need a smart plan, a trustworthy care team, and permission to ask questions before worry turns into a full-time job.

Conclusion

Infections in pregnancy can affect the baby in different ways, from mild newborn illness to serious complications such as preterm birth, low birth weight, hearing loss, vision problems, developmental delays, or pregnancy loss. But knowledge changes the story. Many risks can be reduced with prenatal screening, safe food practices, vaccination, hygiene, STI testing, early treatment, and quick communication with a healthcare provider.

The goal is not to make pregnancy feel like a nine-month obstacle course. It is to help you understand which infections matter, what symptoms deserve attention, and what steps actually protect the baby. Pregnancy may come with cravings, swollen ankles, and an impressive number of opinions from strangers, but it also comes with modern prenatal care. Use it. Ask questions. Get tested. Wash hands. Heat the deli meat. And when something feels off, call the professional humans who went to school for this.