Pregnancy reshapes the immune system in complex ways that heighten susceptibility to certain infectious diseases while simultaneously blunting early clinical warning signs. This immunologic shift, characterized by altered cell-mediated immunity, modulated inflammatory responses, and physiologic adaptations that support fetal development, creates a paradox in prenatal care: Infections that are mild or self-limited outside pregnancy can progress more rapidly and cause serious maternal, fetal, or neonatal complications.1-3
The American College of Obstetricians and Gynecologists (ACOG) emphasize this physiology as a key reason why prevention counseling, early screening, and evidence- based vaccination must be integrated into the earliest prenatal encounters.4 Yet many pregnant patients underestimate their vulnerability and remain unclear about which exposures — respiratory, foodborne, environmental, or bloodborne — carry the greatest risk. These gaps in real-world counseling contribute to preventable morbidity, delayed diagnoses, and missed opportunities for timely intervention.
This disconnect shows up frequently in routine obstetric practice, according to Sheema Khan-Simba, MD, an obstetrician-gynecologist (OB-GYN) at Marietta OB-GYN Affiliates in Marietta, Georgia. “Patients often assume they will handle infections the same way they did before pregnancy, but their physiologic response is completely different now,” according to Dr Khan-Simba. “That is why we make prevention, screening, and vaccination such central parts of early prenatal visits — it changes the trajectory of care.”
Together, these physiologic changes and communication gaps highlight the need for consistent, guideline-aligned strategies to reduce infectious-disease-related complications during pregnancy.
Prevention and Lifestyle Counseling: The First Line of Defense
Since vulnerability increases early in pregnancy, ACOG designates preventive counseling as a core component of the initial prenatal visit. Effective counseling prioritizes exposures that meaningfully influence maternal and fetal outcomes, particularly, foodborne pathogens, cytomegalovirus (CMV), toxoplasmosis, and respiratory viruses, and addresses the misconceptions that commonly shape patient behavior.4
Food Safety and Listeria Prevention
Although listeriosis remains uncommon, pregnancy confers a heightened risk for severe illness and fetal loss, making food-safety counseling essential. ACOG advises avoiding unpasteurized dairy products, soft cheeses made from unpasteurized milk, refrigerated pâtés, and deli meats unless reheated until steaming; all meats, poultry, and leftovers should be cooked thoroughly.5
Dr Khan-Simba finds that many patients focus on the wrong foods. “Patients come in terrified of a long list of foods,” she said. “They will worry about a bite of soft cheese but will not think twice about eating deli meats or old leftovers. Helping them sort myth from meaningful risk makes the biggest difference.”
Toxoplasmosis and Environmental Exposures
Preventing toxoplasmosis requires a combination of household and environmental strategies. Current guidance and expert reviews recommend several practical strategies: avoiding cat litter when possible; having another household member handle litter box changes; using gloves if handling is unavoidable; changing litter daily to prevent oocyst maturation; wearing gloves while gardening; and carefully washing fruits and vegetables.6-8
“A lot of pregnant patients assume the family cat is the biggest problem,” Dr Khan-Simba said. “But most exposures come from soil or food. Once we explain that simple steps — washing produce, wearing gloves, avoiding old litter — are what really matter, they feel relieved rather than restricted.”
CMV Risk Reduction for Pregnant Patients: Childcare, Household, and Health Care Exposures
CMV is one of the most common congenital infections in the United States, yet few pregnant patients are aware of it.9 Current guidance recommends reinforcing hand hygiene, avoiding saliva exposure, and not sharing cups, utensils, or toothbrushes, especially for pregnant patients with toddlers or those working in childcare and health care settings.10,11
“In our practice, many patients work in schools, daycares, or health care settings,” Dr Khan-Simba said. “Teaching simple hygiene strategies makes a real difference to these populations — and it is often precautions they have never considered before.””
Occupational and Seasonal Respiratory Exposures
Given the increased severity of influenza and COVID-19 in pregnancy, ACOG recommends discussing occupational exposures for patients working in health care, childcare, or crowded environments.12,13Even routine respiratory illnesses can worsen more rapidly in pregnancy, making prevention strategies and early evaluation essential.
“I tell patients that even if they did not follow certain precautions before, pregnancy is when their susceptibility is higher,” Dr Khan-Simba said. “Their risk profile truly changes.”
Together, these prevention strategies establish the foundation for safe prenatal care and prepare patients for the role of screening and vaccination later in pregnancy.
Patients often assume they will handle infections the same way they did before pregnancy, but their physiologic response is completely different now. That is why we make prevention, screening, and vaccination such central parts of early prenatal visits — it changes the trajectory of care.
Early Screening and Detection: Aligning Practice With Guideline Standards
Evidence-based infectious-disease screening remains one of the most effective tools for preventing maternal and neonatal morbidity. ACOG recommends universal first- trimester screening for several high-impact infections, emphasizing that early identification enables timely treatment, reduces vertical transmission, and decreases severe maternal illness.14
Universal First-Trimester Screening
ACOG’s recommended first-trimester laboratory panel includes:14
- HIV;
- Syphilis serology;
- Hepatitis B surface antigen;
- Hepatitis C;
- Chlamydia and gonorrhea (universally for patients ≤24 years; risk-based for older patients);
- Urine culture for asymptomatic bacteriuria; and,
- Tuberculosis screening when indicated by risk.
Several of these tests, particularly HIV, syphilis, hepatitis B, hepatitis C, and urine culture, are recommended for all pregnant patients because many infections are asymptomatic yet carry substantial fetal risk.14
Dr Khan-Simba notes that this is where patients often question the need for universal testing. “Many people in stable monogamous relationships ask why they need sexually transmitted infection (STI) testing,” she said. “I explain that most of these infections are silent but can severely harm the baby if missed. Once they understand screening is about protecting the pregnancy — not making assumptions about their personal life — the conversation shifts.”
Repeat Screening in Later Pregnancy
Rising national rates of congenital syphilis have led ACOG to strengthen recommendations: serologic syphilis testing should occur at the first prenatal visit, again during the third trimester, and again at delivery.15 Repeat HIV and STI screening is advised when ongoing risk is present or local epidemiology warrants it.15-17
This approach mirrors local patterns in Georgia. “We routinely repeat HIV and syphilis at 28 weeks,” Dr Khan-Simba said. “Our health system also performs universal admission screening because rates are increasing. We catch cases we would have otherwise missed.”
Recognizing Red-Flag Symptoms
Laboratory shifts in pregnancy can obscure early signs of infection. Physiologic leukocytosis, baseline nausea, and mild dyspnea make early diagnoses more challenging, so clinicians are encouraged to escalate evaluation when patients present with the following:18
- Fever, especially if persistent;
- Rash or mucocutaneous findings;
- New or worsening respiratory symptoms;
- Gastrointestinal illness with systemic signs; and,
- Neurologic changes, such as severe headache or confusion.
“Pregnancy changes the baseline,” Dr Khan-Simba emphasized. “We cannot rely on white blood cell counts alone. It has to be a clinical diagnosis supported by labs — not the other way around.”
Vaccination in Pregnancy: Timing, Safety, and Counseling
Vaccination remains one of the most effective strategies for reducing infectious-disease morbidity in pregnancy. Current guidance emphasizes that immunization protects both the pregnant individual and the fetus, with maternal antibodies providing early neonatal immunity. Despite extensive safety data, vaccine hesitancy persists, particularly regarding COVID-19, which makes clear, evidence-based counseling essential.
Core Vaccines Recommended in Pregnancy
- Influenza (any trimester): Recommended because pregnant individuals are more likely to experience severe complications such as pneumonia and respiratory failure.12
- Tdap (27-36 weeks each pregnancy): Protects newborns from pertussis by maximizing maternal antibody production.19
- Respiratory syncytial virus (RSV) vaccine (32-36 weeks during RSV season): Reduces severe RSV-associated lower respiratory tract infections in infants.19
- COVID-19 vaccine and boosters: Strongly recommended by ACOG due to the increased risk for severe maternal illness, intensive care unit admission, and mechanical ventilation. This stance remains unchanged despite federal shifts in Centers for Disease Control and Prevention (CDC) policy, reflecting substantial maternal-fetal safety and efficacy data.13
Addressing Vaccine Hesitancy
Dr Khan-Simba sees hesitation rooted primarily in fear of harming the pregnancy. She begins this conversation by exploring the patient’s reasoning. “I ask patients, ‘What concerns are you weighing?’ Most think avoiding the vaccine protects the baby,” she said. “That opens the door to explaining that the vaccine does not cross the placenta — the antibodies do. And those antibodies are what protect their newborn.”
Her approach centers on transparency. “These vaccines have been extensively studied, and the evidence does not suggest adverse pregnancy outcomes. The risk is from the diseases themselves,” she emphasized.
Shared Decision-Making and Complex Infectious-Disease Scenarios
Many infectious risks in pregnancy can be managed with standard prevention, screening, and vaccination. Others require individualized counseling and coordinated care among obstetrics, infectious disease, and maternal-fetal medicine.
Balancing Treatment Risks and Disease Risks
Pregnancy often requires weighing the theoretical risks for a medication against the known risks for untreated illness. For influenza, ACOG recommends empiric oseltamivir treatment for suspected or confirmed disease because the maternal complications of untreated influenza far outweigh any medication concerns.12Similar urgency applies to infections such as HIV, syphilis, and hepatitis B, where vertical transmission risk is closely tied to viral load and treatment timing.15-17
Dr Khan-Simba described a recent case involving a pregnant patient with HIV whose severe hyperemesis disrupted adherence to antiretroviral therapy. “Her viral load started rising quickly, and suddenly we were approaching a threshold at which a vaginal delivery might not be safe,” she said. “We worked closely with infectious disease to find a regimen she could tolerate and aggressively treated her nausea. With coordinated care, we achieved an undetectable viral load by delivery.”
Communicating Uncertainty and When to Involve Specialists
Shared decision-making becomes especially important when navigating limited evidence or evolving guidance — for example, during emerging measles outbreaks or shifting COVID-19 policies. “I tell patients: ‘Here is what we know, here is what we do not know, and here is the recommendation based on current evidence,’” Dr Khan-Simba said. “Patients appreciate honesty and transparency more than certainty.”
In Dr Khan-Simba’s experience, certain clinical scenarios warrant earlier involvement of infectious disease or maternal-fetal medicine specialists. In her practice, she refers patients promptly when HIV viral loads rise, hepatitis B or C titers are elevated, respiratory infections are severe or atypical, congenital infections are suspected, or when patients report significant exposures to varicella, measles, or parvovirus B19.
Coordinated care ensures unified messaging, timely treatment, and consistent follow-up.
Integrating Evidence, Communication, and Shared Understanding
Across the prenatal timeline, the core elements of infectious disease management — early prevention, thoughtful screening, timely vaccination, and open communication — function as the backbone of maternal-fetal safety. But in practice, these components only work when patients understand why each recommendation matters.
“As patients come to understand how their physiology has changed, why certain infections pose greater risks, and how each recommendation fits into a larger protective plan, their mindset shifts,” said Dr Khan-Simba. “When patients grasp the why behind our advice, their perspective changes — they feel empowered rather than overwhelmed,” she added.
Clinicians and patients have several reliable resources to support this initiative. ACOG’s immunization and patient-education materials provide clear, evidence-based explanations for routine care.21 Society for Maternal-Fetal Medicine’s consult series offers more nuanced guidance for complex scenarios.22 Local public health updates help clinicians tailor risk discussions based on regional trends.23
When these tools are woven into routine care, they help clinicians deliver counseling that is evidence-based, guideline-aligned, and meaningfully centered on each patient’s lived reality. Ultimately, this approach strengthens outcomes across the prenatal continuum and reinforces the trust that anchors every effective patient-clinician partnership.
This article originally appeared on Infectious Disease Advisor
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