COVID-19 during pregnancy: Effects on the placenta and stillbirth risk

Why the placenta matters so much

The placenta is a temporary organ with a full-time job and absolutely no vacation days. It attaches to the uterus, connects with the fetus through the umbilical cord, and manages the exchange of oxygen, nutrients, antibodies, carbon dioxide, and waste products.

Maternal and fetal blood normally remain separate. Oxygen and nutrients move across specialized placental tissue into the fetal circulation, while waste products travel in the opposite direction. The placenta also produces hormones, helps regulate maternal metabolism, and forms part of the immune barrier protecting the developing baby.

Because the placenta functions partly like the fetus’s lungs, kidneys, digestive system, and hormone factory, widespread placental damage can become dangerous quickly. If blood flow or gas exchange is significantly reduced, the fetus may receive less oxygen even when the virus never enters the fetal bloodstream.

How COVID-19 can affect the placenta

COVID-19 may influence placental health through several overlapping pathways. The effects vary considerably according to the severity and timing of infection, the viral variant, vaccination history, maternal health conditions, and individual immune response.

Maternal inflammation

SARS-CoV-2 can trigger a strong inflammatory response. In severe disease, inflammatory chemicals circulating in maternal blood may affect blood vessels throughout the body, including the vessels supplying the uterus and placenta. This can contribute to endothelial injury, abnormal clotting, or reduced placental perfusion.

Vascular malperfusion

Researchers examining placentas after maternal COVID-19 have sometimes identified signs of maternal or fetal vascular malperfusion. In plain English, blood may not have moved through parts of the placenta as efficiently as expected. These findings can include small clots, damaged vessels, infarcts, or areas receiving inadequate blood.

Importantly, these abnormalities are not unique to COVID-19. Similar findings can occur with high blood pressure, preeclampsia, diabetes, fetal growth restriction, smoking, and other pregnancy complications. Some studies have found more vascular lesions after COVID-19, while others have found no distinctive placental pattern, particularly after mild infection. In one prospective U.S. cohort, no placental SARS-CoV-2 infection was detected, although vascular abnormalities became more likely as maternal disease severity increased.

Direct placental infection

Direct infection of placental tissue is possible but uncommon. The placenta appears to possess several biological defenses that make viral entry difficult. Maternal virus circulating in the blood, known as viremia, is also relatively uncommon in typical COVID-19 cases.

This helps explain why vertical transmission from mother to fetus is rare. A positive maternal test does not automatically mean the placenta is infected, and an infected placenta does not automatically mean the fetus has contracted COVID-19.

What is SARS-CoV-2 placentitis?

SARS-CoV-2 placentitis is a specific form of severe placental injury associated with direct infection of placental cells. Pathologists commonly identify it through a combination of three microscopic findings:

• Chronic histiocytic intervillositis: inflammatory immune cells accumulate in spaces involved in maternal-fetal exchange.
• Perivillous fibrin deposition: fibrin-like material builds up around placental villi and blocks exchange surfaces.
• Trophoblast necrosis: cells forming the placenta’s protective outer barrier become damaged or die.

Together, these changes can replace functioning placental tissue with inflammation, dead cells, and fibrin. It is a little like covering an air filter with glue: the system may still be physically present, but oxygen exchange becomes severely restricted. This recognized triad distinguishes true SARS-CoV-2 placentitis from the milder, nonspecific abnormalities occasionally reported after infection.

When damage becomes widespread, placental insufficiency may develop rapidly. The fetus can experience oxygen deprivation, also called hypoxia, even without direct viral infection. Reviews of placentitis-associated losses indicate that fetal death may result primarily from placental destruction and hypoxic-ischemic injury rather than the virus attacking fetal organs.

This condition is serious, but it is also rare. Most placentas examined after maternal COVID-19 do not show catastrophic SARS-CoV-2 placentitis.

Does COVID-19 during pregnancy increase stillbirth risk?

Evidence indicates that maternal COVID-19 can increase stillbirth risk, particularly when infection is severe or occurred during periods dominated by more virulent variants. A stillbirth in the United States generally means pregnancy loss at or after 20 weeks and before birth.

A major CDC analysis examined more than 1.2 million U.S. delivery hospitalizations between March 2020 and September 2021. Stillbirth occurred in 1.26% of deliveries involving a documented COVID-19 diagnosis, compared with 0.64% of deliveries without one. After adjustment, the relative risk was approximately 1.9 times higher.

The difference was especially pronounced during the Delta period. The adjusted risk was approximately four times higher among deliveries with COVID-19 than among those without it. Stillbirth remained uncommon overall, but the increase was medically meaningful.

These historical numbers should not be treated as a prediction for every infection today. The study largely reflects the pre-vaccine and early-vaccine eras, and it could not account for individual vaccination status. Viral variants, immunity, treatment availability, and population behavior have changed. Delta-era percentages should therefore not be pasted onto every modern case like an outdated price tag.

Other studies have produced somewhat different estimates because they examined different variants, populations, gestational periods, and definitions of infection. Some found the greatest danger in the first several weeks after infection, while others suggested that infections during early or middle pregnancy may have different effects from third-trimester disease. The overall message is more reliable than any single number: risk is elevated in some circumstances, but the absolute chance of stillbirth remains low for most infected pregnant patients.

Who may face a higher risk of complications?

No checklist can predict exactly whose placenta will be affected. Nevertheless, closer attention may be appropriate when COVID-19 occurs alongside other factors associated with severe maternal illness or placental dysfunction, including:

• Moderate, severe, or critical COVID-19 symptoms
• Low blood oxygen or significant breathing difficulty
• Maternal hospitalization or intensive care
• High blood pressure, chronic hypertension, or preeclampsia
• Diabetes, obesity, or certain cardiovascular conditions
• Placental abruption or abnormal bleeding
• Fetal growth restriction
• Multiple pregnancy, such as twins or triplets
• Lack of prior vaccination or immunity, especially during more severe variant waves

The CDC study found that severe maternal complicationsincluding respiratory distress, sepsis, shock, intensive care admission, and mechanical ventilationwere associated with a higher prevalence of stillbirth among deliveries involving COVID-19.

Can doctors detect placental damage during pregnancy?

Placental inflammation itself usually cannot be definitively diagnosed without examining placental tissue after delivery. Routine ultrasound does not provide a microscopic view of trophoblast necrosis or intervillositis. However, prenatal care can identify possible consequences of reduced placental function.

Ultrasound and fetal growth

An ultrasound may evaluate fetal growth, amniotic fluid volume, placental appearance, and blood flow. Doppler ultrasound can assess circulation in the umbilical cord or other fetal vessels when clinically indicated. Not everyone who recovers from mild COVID-19 needs repeated scans; follow-up should be individualized according to gestational age, symptoms, health history, and obstetric findings.

Nonstress tests and biophysical profiles

Later in pregnancy, clinicians may use a nonstress test to evaluate the fetal heart-rate response to movement. A biophysical profile combines ultrasound observations with heart-rate monitoring. These tests can offer useful information about current fetal well-being, but they cannot guarantee that complications will not develop later.

Fetal movement awareness

A noticeable reduction or change in the baby’s usual movement pattern deserves immediate attention. Do not spend hours drinking cold juice, poking your abdomen, or waiting for the baby to “wake up” while anxiety climbs the walls. Contact the obstetric care team or labor and delivery unit promptly and follow its instructions.

What to do after testing positive while pregnant

1. Contact your healthcare provider early. Report the positive test, symptoms, gestational age, vaccination history, medications, and underlying conditions.
2. Ask about antiviral treatment promptly. Some COVID-19 treatments must begin within the first few days of symptoms. Current guidance states that effective treatment should not automatically be withheld solely because a patient is pregnant or breastfeeding. Medication interactions and individual risks still require professional review.
3. Monitor breathing and overall condition. Seek urgent help for trouble breathing, persistent chest pain, confusion, fainting, bluish or pale lips, severe dehydration, or rapidly worsening symptoms.
4. Watch for obstetric warning signs. Urgent evaluation is warranted for decreased fetal movement, vaginal bleeding, leaking fluid, regular painful contractions, severe abdominal pain, a severe persistent headache, vision changes, or sudden swelling.
5. Keep prenatal appointments. The office may adjust timing or infection-control arrangements, but routine obstetric care remains important.
6. Avoid self-prescribing medications. “Natural” does not automatically mean pregnancy-safe, and somebody’s enthusiastic social-media comment is not a pharmacology degree.

Vaccination, placental health, and stillbirth prevention

Large studies have not found that COVID-19 vaccination during pregnancy increases the risk of miscarriage, birth defects, preterm delivery, or stillbirth. Vaccination lowers the likelihood of severe maternal disease and may reduce infection-related preterm birth and stillbirth. It also produces maternal antibodies that can cross the placenta and help protect infants during their first months of life.

CDC guidance for the 2025–2026 season uses individual clinical decision-making while emphasizing that vaccination offers substantial benefit to people at higher risk of severe illness, including pregnant patients. The Society for Maternal-Fetal Medicine also supports updated COVID-19 vaccination during pregnancy. Decisions should account for current recommendations, previous doses, recent infection, underlying conditions, exposure risk, and the stage of pregnancy.

Vaccination cannot prevent every infection or every placental complication. It is risk reduction, not an invisible force field. Even so, reducing the chance of severe disease is valuable because severe maternal illness is consistently linked with worse pregnancy outcomes.

Common misconceptions about COVID-19 and the placenta

“A positive test means the baby is infected.”

False. Vertical transmission is possible but uncommon. Most maternal infections do not result in detectable placental or fetal infection.

“Any abnormal placenta after COVID-19 proves the virus caused it.”

False. Blood clots, inflammation, infarcts, and vascular abnormalities can have many causes. Confirmed SARS-CoV-2 placentitis requires a specific combination of pathological and virological evidence.

“Mild symptoms mean there is zero pregnancy risk.”

Not quite. Serious complications are much less likely after mild illness, but unusual symptoms or reduced fetal movement should never be ignored.

“COVID-19 vaccination causes stillbirth.”

Large observational studies do not support this claim. Available evidence shows no increased stillbirth risk from vaccination and suggests vaccination may help prevent poor outcomes related to maternal infection.

Experience-based lessons from pregnancy during COVID-19

The following composite situations reflect common concerns and care patterns rather than the experiences of one identifiable patient. They are educational examples, not substitutes for medical evaluation.

Experience 1: A mild infection can still feel emotionally enormous

A patient at 22 weeks develops nasal congestion, fatigue, a low fever, and a positive home test. Physically, the illness remains mild. Emotionally, every cough feels connected to the placenta, and every quiet moment creates another frightening question.

The most helpful first step is often a prompt conversation with the obstetric team. The clinician reviews symptoms, medications, risk factors, and eligibility for antiviral treatment. The patient receives clear instructions about hydration, fever management, breathing symptoms, and when to seek urgent care. A plan replaces endless internet searching, which is rarely known for its calming bedside manner.

The pregnancy continues normally. This is an important experience to remember: many pregnant people contract COVID-19, recover, and deliver healthy babies without evidence of placental injury.

Experience 2: Severe symptoms change the monitoring plan

Another patient develops shortness of breath, persistent fever, and falling oxygen levels during the third trimester. Hospital care focuses first on stabilizing maternal breathing because the health of the pregnant patient and fetus are tightly connected. Oxygen support, laboratory testing, antiviral therapy, fetal heart-rate monitoring, and obstetric consultation may all become part of care.

After recovery, clinicians may recommend additional fetal surveillance or growth assessment based on disease severity and the pregnancy’s overall condition. The lesson is not that every severe infection will damage the placenta. It is that severe maternal illness deserves active treatment and coordinated maternal-fetal care rather than a “let’s see what happens” approach.

Experience 3: Reduced fetal movement should override the fear of overreacting

A patient recovers from COVID-19 and later notices that the baby is moving much less than usual. She worries that calling the hospital will make her seem anxious. The better choice is to call.

Healthcare teams would rather evaluate ten reassuring movement concerns than miss one fetus in distress. Testing may show a healthy, active baby, allowing everyone to exhale. If a problem is present, early evaluation can create options for monitoring, treatment, or delivery. Fetal movement is not a perfect placental test, but a meaningful change is never something a patient must diagnose alone.

Experience 4: Placental pathology can provide answers after a loss

In the rare and devastating situation of stillbirth after maternal COVID-19, examination of the placenta may reveal extensive inflammation, fibrin deposition, trophoblast injury, or direct viral involvement. Families sometimes learn that the fetus was not infected; instead, the placenta could no longer deliver enough oxygen.

This information cannot undo the loss, but it may help explain what happened and guide counseling about a later pregnancy. It also matters emotionally: placental failure is not caused by a parent worrying too much, working one busy afternoon, sleeping in the wrong position once, or missing some imaginary perfect-pregnancy rule.

Experience 5: The next pregnancy deserves planning, not automatic panic

After a previous COVID-associated placental complication, a patient may enter another pregnancy expecting history to repeat itself. Current literature suggests that SARS-CoV-2 placentitis is not generally considered a predictably recurring placental disorder. Nevertheless, future care should be personalized according to the previous pathology report, maternal medical conditions, vaccination status, blood pressure, fetal growth, and other obstetric factors.

A preconception or early-pregnancy consultation can turn a vague fear into a concrete monitoring plan. That plan may include reviewing the previous loss, updating vaccinations, controlling chronic conditions, discussing medication, and identifying exactly whom to call when concerns arise.

Conclusion

COVID-19 during pregnancy can affect the placenta through inflammation, altered blood flow, vascular injury, orrarelydirect infection. Severe SARS-CoV-2 placentitis may destroy functioning placental tissue and reduce oxygen delivery enough to cause fetal injury or stillbirth, even when the fetus itself is not infected.

Stillbirth remains an uncommon outcome, and most pregnancies affected by COVID-19 do not end in loss. The greatest concerns have been associated with severe maternal disease, certain underlying conditions, lack of immunity, and more dangerous viral periods such as the Delta wave. Vaccination, early communication with an obstetric provider, timely treatment, appropriate monitoring, and immediate evaluation of reduced fetal movement offer a far more useful response than fear.