What is mother-to-child transmission (vertical transmission)? At which stages does it occur?

Vertical TransmissionMother-to-Child TransmissionPregnancyChildbirthBreastfeedingHIV/AIDS
Created At: 8/15/2025Updated At: 8/17/2025
Answer (1)

Okay, let's talk about this topic.

What is Mother-to-Child Transmission (Vertical Transmission)?

Simply put, Mother-to-child transmission (MTCT), also called vertical transmission, refers to an infected mother (e.g., with HIV) passing the virus to her baby during pregnancy, childbirth, or breastfeeding.

You can think of it as a pathway passed vertically from mother to child – the mother being the "top" and the baby the "bottom", which is why medicine uses the slightly more technical term "vertical transmission". These two terms mean the same thing.

This doesn't happen with all diseases; it mainly pertains to those like HIV, hepatitis B, and syphilis, which can spread through blood and bodily fluids.

At what stages does it mainly occur?

MTCT doesn't happen in just one instant; it can occur at any stage from pregnancy through breastfeeding. There are three main phases:

1. During Pregnancy (Transmission via the Placenta)

  • When? Throughout pregnancy, but mainly in the mid-to-late stages.
  • How does it happen? The mother and baby are connected by the placenta, the baby's lifeline for nutrients. Normally, the placenta acts as a protective barrier, blocking many harmful substances. However, if the mother has a high level of HIV in her body (a high viral load), the virus can potentially "break through" this barrier and enter the baby's body via the placenta.
  • Proportion of risk: Accounts for about one third of all MTCT cases.

2. During Delivery (Transmission at Birth)

  • When? During childbirth, whether vaginal or cesarean section.
  • How does it happen? This is the primary mode of transmission. During delivery, the baby is exposed to the mother's blood, amniotic fluid, and vaginal secretions, all of which contain HIV. If the baby has tiny breaks in their skin (which are very common during birth), the virus can easily enter the baby's body through these "minor wounds".
  • Proportion of risk: This is the stage with the highest risk, accounting for more than half of all MTCT cases.

3. During Breastfeeding (Transmission through Breast Milk)

  • When? After the baby is born, throughout the breastfeeding period.
  • How does it happen? HIV is present in the mother's breast milk. When the baby suckles, the virus enters the baby's digestive tract along with the milk. Additionally, the mucous membrane lining a newborn's digestive tract is very delicate and not fully developed, making it easier for the virus to cross this "defense line" and enter the bloodstream, causing infection.
  • Proportion of risk: Accounts for about 10% to 15%, with the risk increasing the longer the breastfeeding duration.

A very important addition:

While this sounds alarming, the good news is that mother-to-child transmission of HIV is now completely preventable!

If an HIV-positive mother starts receiving standard antiretroviral therapy (ART) during pregnancy (often called "prevention of mother-to-child transmission" or PMTCT treatment), successfully suppresses the virus in her body to a very low level (even undetectable), chooses a safe delivery method (like C-section) under medical guidance, provides her baby with a course of preventative medication after birth, and consistently uses formula feeding (replacing breast milk), the baby's chance of contracting HIV can be reduced from 30%-40% down to less than 1%.

Therefore, early detection and standardized treatment are key to protecting the baby's health.

Created At: 08-15 04:45:09Updated At: 08-15 09:31:51