When a person living with Human Immunodeficiency Virus (HIV) becomes pregnant, the primary concern is whether the virus will be passed to the baby. Modern medicine has dramatically lowered this risk, making transmission rare in countries with robust healthcare systems. When a pregnant person adheres to an established medical protocol, the chance of the baby acquiring HIV is typically less than two percent, and often under one percent. This success is achieved through carefully managed medical interventions known as the prevention of mother-to-child transmission (PMTCT) protocol.
Understanding Mother-to-Child Transmission
The transmission of HIV from a pregnant person to their child, known as perinatal or vertical transmission, can occur during three distinct periods. Transmission can occur during pregnancy, where the virus crosses the placenta and infects the fetus. The majority of transmissions, however, occur during labor and delivery, when the baby is exposed to the mother’s blood and other bodily fluids.
The third period is postpartum, specifically through breastfeeding. The most significant factor influencing the risk of transmission is the pregnant person’s viral load, which is the amount of HIV detectable in the blood. A higher viral load correlates directly with a higher likelihood of the baby acquiring the virus.
Critical Steps for Prevention During Pregnancy
The primary strategy for preventing transmission is the consistent use of Antiretroviral Therapy (ART) throughout the pregnancy. ART consists of medications that stop the virus from multiplying. The goal is to achieve a sustained undetectable viral load, meaning the level of HIV in the blood is too low to be measured by standard tests. An undetectable viral load significantly reduces the risk of transmission to below one percent.
It is important to begin ART as soon as possible, ideally before conception or immediately upon learning of the pregnancy. Consistent adherence ensures the viral load remains suppressed, protecting both the pregnant person’s health and the baby. The choice of delivery method (vaginal or Cesarean section/C-section) is determined by the viral load measured near delivery. If the viral load is suppressed (typically 1,000 copies/mL or less), a vaginal delivery is considered safe.
If the viral load remains detectable (over 1,000 copies/mL) near the time of birth, a scheduled C-section is usually recommended. This surgical delivery reduces the baby’s direct contact with maternal blood and secretions, lowering the risk of transmission. An intravenous infusion of an antiretroviral drug may also be administered during labor in high-risk situations for extra protection.
Monitoring and Testing the Newborn
After birth, the newborn receives prophylactic antiretroviral medication immediately, ideally within six hours. This medication is given for four to six weeks to prevent any virus that may have entered the baby’s system from establishing a permanent infection. The specific regimen depends on the mother’s viral load during pregnancy and delivery.
Standard HIV antibody tests cannot be used to diagnose HIV in newborns because the baby carries the mother’s antibodies for several months. Instead, the baby is tested using a virologic assay, such as a Polymerase Chain Reaction (PCR) test, which directly looks for the genetic material of the virus. Diagnostic testing is performed at birth, four to six weeks of age, and again at four to six months of age.
A definitive diagnosis of HIV infection requires two separate positive virologic tests. If all tests are negative at the four-to-six-month mark, and the baby has not been breastfed, the child is confirmed to be HIV-negative. Continued monitoring of the infant’s overall health and development remains part of the routine care plan.
Considerations for Postpartum Care and Breastfeeding
For mothers in high-resource settings where safe, affordable alternatives are readily available, the recommendation is typically to use formula. This choice completely eliminates the risk of HIV transmission through breast milk, which, though very low with a suppressed viral load, is not zero. The decision to avoid breastfeeding ensures the lowest possible risk of transmission.
However, some women with a sustained undetectable viral load may choose to breastfeed under strict medical supervision. This approach requires the mother to remain consistently adherent to ART and involves frequent viral load testing for both the mother and the baby throughout breastfeeding. Any detectable viral load in the mother necessitates an immediate cessation of breastfeeding to protect the infant.
Regardless of the feeding choice, the mother must continue her lifelong ART regimen for her own health and to maintain viral suppression. Postpartum care includes robust support to ensure the mother remains engaged in care, as adherence can sometimes be more challenging after delivery. Continued pediatric follow-up remains necessary for the child to monitor for any delayed transmission and to ensure they meet all developmental milestones.