Syphilis and Human Immunodeficiency Virus (HIV) are two sexually transmitted infections (STIs) that can cross the placenta, potentially infecting the baby during pregnancy.
The ability of an STI to cross the placenta means the infection can be transmitted from the mother directly to the fetus while still in the womb. This is a crucial distinction from STIs that primarily transmit during the birth process when the baby passes through the birth canal.
Understanding Placental Transmission
The placenta acts as a lifeline between a pregnant person and their developing baby, facilitating nutrient and oxygen exchange. However, some pathogens, including certain STIs, can breach this protective barrier.
Syphilis
Syphilis, caused by the bacterium Treponema pallidum, is well-known for its ability to readily cross the placenta. This can lead to what is known as congenital syphilis, a serious condition that can cause significant health problems for the baby, including:
- Miscarriage or stillbirth
- Premature birth
- Low birth weight
- Deformities
- Severe anemia
- Liver and spleen enlargement
- Jaundice
- Brain and nerve problems (e.g., blindness, deafness)
The risk and severity of congenital syphilis depend on the stage of the infection in the pregnant individual. Early detection and treatment during pregnancy are crucial for preventing these devastating outcomes.
HIV
HIV can also cross the placenta, leading to what is called perinatal or mother-to-child transmission (MTCT). While HIV can be transmitted across the placenta during pregnancy, it can also be transmitted to the baby during delivery (through exposure to blood and other body fluids in the birth canal) and through breastfeeding.
Without intervention, the risk of HIV transmission from a mother to her baby can be significant. However, with modern medical advancements, including antiretroviral therapy (ART) for pregnant individuals with HIV, the risk of transmission can be dramatically reduced, often to less than 1%.
Other Modes of Maternal-to-Child Transmission
While syphilis and HIV are notable for placental transmission, it's important to understand that other STIs can be passed from mother to baby through different routes, primarily during delivery as the baby passes through the birth canal.
During Delivery (Birth Canal)
Several STIs can infect the baby upon exposure during a vaginal birth. These include:
- Gonorrhea: Can cause eye infections (ophthalmia neonatorum) and, less commonly, lead to blindness, joint infections, or blood infections in newborns.
- Chlamydia: Can cause eye infections and pneumonia in newborns.
- Hepatitis B: Can lead to chronic liver infection in the baby, increasing the risk of liver disease and cancer later in life.
- Genital Herpes: Can cause severe, life-threatening infections in newborns if the baby is exposed to active lesions during delivery. This can affect the brain, skin, eyes, and other organs.
Summary of STI Transmission to Baby
To illustrate the different routes of maternal-to-child transmission for common STIs, refer to the table below:
| STI | Primary Maternal-to-Child Transmission Route(s) |
|---|---|
| Syphilis | Across the placenta (in utero/in the womb) |
| HIV | Across the placenta, during delivery (birth canal), and during breastfeeding |
| Gonorrhea | Primarily during delivery (birth canal) |
| Chlamydia | Primarily during delivery (birth canal) |
| Hepatitis B | Primarily during delivery (birth canal) |
| Genital Herpes | Primarily during delivery (birth canal), especially with active lesions |
Importance of Screening and Prevention
Given the potential for serious health consequences for newborns, routine STI screening is a critical component of prenatal care for all pregnant individuals. Early detection allows for timely treatment, which can prevent or significantly reduce the risk of transmission to the baby and improve outcomes. For more information on STIs and pregnancy, you can consult reputable sources such as the Centers for Disease Control and Prevention (CDC).
