Vertical Transmission

What is vertical transmission?

Vertical transmission is when a fetus or baby gets an infection during pregnancy or childbirth, or soon after birth through breastfeeding. Germs (pathogens) like viruses, bacteria and parasites can cause these infections.

It might seem like getting sick while pregnant is no big deal. But even if your symptoms are mild, the effects of an infection on a fetus or newborn can be serious. Vertical transmission can cause miscarriage, stillbirth and congenital (present-at-birth) conditions that last a lifetime.

Types of vertical transmission

Types of vertical transmission include:

• In utero/transplacental. This is when a germ moves through a pregnant woman’s bloodstream, across the placenta, to infect the fetus.
• Intrapartum. This is when your baby is infected during birth, while going through the birth canal.
• Postpartum. This is when your baby gets infected from breastfeeding — either through breast milk or blood from cracked nipples.

What’s the difference between vertical transmission and horizontal transmission?

Both vertical and horizontal transmission happen when a germ spreads from person to person.

Horizontal transmission is what we usually think of when something is contagious — you can get it from contact with another person through coughing, sneezing, sex or a shared item.

Vertical transmission is specifically when an infection spreads from a pregnant or breastfeeding woman to a fetus or baby.

Many vertically transmitted diseases can also spread horizontally.

What are the symptoms of vertical transmission?

Symptoms of vertically transmitted infections in babies include:

• Blindness or vision loss
• Hearing loss
• Heart disease
• Rash or blisters
• Seizures
• Yellowish skin and eyes (jaundice)
• Pink eye (conjunctivitis)
• Small, widely spaced teeth (notched teeth)
• Facial differences
• Enlarged liver (hepatomegaly) and/or spleen (splenomegaly)
• Small head size (microcephaly)
• Delays or differences in motor skill development

Some babies have symptoms at birth. Others develop them later in childhood.

What infections can spread through vertical transmission?

Many viruses, bacteria and parasites can spread through vertical transmission. People often use the acronym “TORCH” to remember them:

• Toxoplasmosis, Treponema pallidum (syphilis)
• Other
• Rubella
• Cytomegalovirus
• Herpes simplex viruses

Infections that can fall under “Other” include:

• Chagas disease
• Chlamydia
• COVID-19
• Gonorrhea
• Hepatitis viruses
• HIV
• Listeriosis
• Parvovirus B19
• Varicella-zoster virus
• Zika virus

How does a pregnant woman get vertically transmitted infections?

Before passing them on to a fetus or baby, a pregnant or breastfeeding woman can get vertically transmitted diseases many ways, including through:

• Oral, anal or vaginal sex
• Respiratory droplets (coughing or sneezing)
• Contact with cat poop
• Eating or drinking something contaminated with a parasite
• The bite of a kissing bug
• A blood transfusion (this is rare, as providers screen donated blood for germs)

What are the complications of vertically transmitted diseases?

Vertical transmission can increase the likelihood of miscarriage or stillbirth. Severe swelling or fluid build-up can also happen inside the fetus (hydrops fetalis).

How do providers diagnose vertically transmitted infections?

Providers can do blood tests during early pregnancy for certain infectious diseases that could infect the fetus. If your provider diagnoses you during pregnancy, they may recommend tests to see if the fetus is also infected. These include:

• Amniocentesis. A provider uses a small needle to collect cells from the fluid surrounding the fetus.
• Chorionic villus sampling. A provider collects samples of tissue from the placenta for testing.
• Fetal blood sampling. A provider uses a thin needle through your belly to get a sample of blood from the fetus.

In newborns and kids, providers can diagnose many vertically transmitted diseases with a blood test. If your provider is concerned about a TORCH infection (either because you have one or your child has symptoms), they’ll screen your baby at birth. Providers may also diagnose infections with urine (pee) tests or swab the inside of your child’s cheek to do a saliva (spit) test.

How are vertically transmitted diseases treated?

Treating vertically transmitted diseases depends on what kind of infection your child has and when they’re diagnosed. Sometimes, your provider can prescribe antiviral, antibiotic or antiparasitic treatment before or after birth.

Medications can sometimes lessen the risk of health problems but may not completely prevent them. And they can’t reverse any damage that’s already been done. Speech and occupational therapy can help children with congenital infections manage the effects of hearing loss and developmental issues.

Can vertical transmission be prevented?

If you have an infectious disease that could be transmitted during pregnancy or delivery, you may be able to treat it with antibiotics, antivirals or antiparasitic medications. This can reduce the risk of it spreading to the fetus or your baby. To avoid infection, you can also:

• Wash your hands frequently with soap and water. Wear gloves for gardening or cleaning and wash your hands afterward.
• Avoid crowded places or wear a mask. This is especially important during cold and flu season and when COVID-19 cases are high.
• Ask your provider about recommended vaccinations. Vaccines can help protect you from some vertically transmitted diseases.
• Practice safe sex. Ask partners to get tested for sexually transmitted infections (STIs) or use condoms during sex when you’re pregnant.
• Avoid changing cat litter yourself when pregnant. If you must change cat litter, wear disposable gloves and wash your hands thoroughly afterward.
• Follow safe cooking habits. This includes properly freezing and cooking meat and thoroughly washing or peeling fruits and vegetables.
• Eat safe foods. Don’t drink unpasteurized milk or untreated water. Don’t eat raw or undercooked clams, oysters or mussels.
• Protect yourself from bug bites. Use insect repellants and wear long sleeves and pants.
• Plan ahead for travel. Consider consulting with a travel medicine clinic if you’ll be traveling overseas while pregnant. They might have additional recommendations specific to your travel destination.

Consider being screened for Chagas disease if you’re pregnant or plan to become pregnant and you’ve been in an area where Chagas spreads.

What can I expect if my child gets a vertically transmitted disease?

What happens if your child gets an illness through vertical transmission depends on many things, including when they got infected and what disease it is. Generally, the earlier in pregnancy a germ is passed to the fetus, the higher the likelihood of pregnancy loss or your baby being born with lifelong conditions.

When should I see my healthcare provider?

Ask your pregnancy care provider about screening for infectious diseases early in pregnancy. Talk to them right away if you think you’ve been exposed to a sexually transmitted infection (STI) or if you get sick during pregnancy.