Epidemiological control and screening of mothers
Prevention of vertical transmission begins with the early detection of the virus in the mother. Comprehensive suspicion and subsequent verification are based on a triad of criteria: clinical, epidemiological, and laboratory.
Pregnant women belong to designated population groups and undergo testing upon registration at the antenatal clinic. According to legal aspects, HIV testing is always strictly voluntary: a mandatory condition is obtaining written informed consent, as well as conducting pre-test and post-test counseling.
If a pregnant woman exhibits clinical markers (e.g., general infection syndrome lasting over a month, persistent recurrent pyoderma, or chronic inflammatory diseases of the reproductive organs of unclear etiology), maximum vigilance is required. Laboratory confirmation of the mother's status is carried out according to a standard three-stage algorithm:
- Screening stage (enzyme-linked immunosorbent assay — ELISA) — screening for HIV antibodies and p24 antigen.
- Reference stage — in-depth analysis of serum using 2–3 different ELISA test systems.
- Expert stage — confirmation of the diagnosis exclusively by Western blot, assessing the presence of specific antibodies to viral glycoproteins (env gene — gp160, gp120, gp41).
Features of serological diagnostics in newborns
Diagnostics of human immunodeficiency virus in children born to HIV-positive mothers has strict limitations. This is due to the phenomenon of transplacental transfer of maternal class G immunoglobulins (IgG) into the fetal bloodstream.
- False-positive period. At birth and during the first months of life, standard antibody serological tests (ELISA and Western blot) will yield a positive result in the majority of such children. It is important to understand: this result reflects the mother's immune status, not the fact of infection of the infant itself.
- Antibody kinetics. If intrauterine or intrapartum (during childbirth) transmission has not occurred, maternal antibodies will gradually be eliminated (degraded and cleared) from the child's body.
- Criterion for deregistration. A definitive serological diagnosis based on the complete absence of HIV antibodies can only be established after a significant period. A child is considered uninfected and deregistered only 1.5 years (18 months) after birth, when complete breakdown of maternal immunoglobulins occurs.
The role of PCR in managing at-risk children
Since antibody evaluation in infants is uninformative due to the maternal immune trace, molecular genetic methods come to the forefront for early detection of the infection.
Polymerase chain reaction (PCR) detects not antibodies, but directly the genetic material of the pathogen — viral RNA or proviral DNA.
Advantages of PCR in this context:
- The method is critically important specifically for special patient groups (newborns or individuals with marked immunosuppression) in whom the production of their own antibodies is either masked or impaired.
- Viral load (VL) — the quantitative content of HIV RNA copies in 1 µl of blood plasma can be assessed via PCR.
- The method is used to identify specific viral subtypes and drug resistance mutations to antiretroviral therapy (ART), which is extremely important for adjusting treatment regimens if viral transmission to the child has nevertheless occurred.
Briefly: answers to topical questions
At what gestational ages is routine screening for HIV infection performed?
Routine screening for HIV infection in pregnant women is performed twice.
- First examination: upon registration for pregnancy.
- Second examination: in the third trimester, at a gestational age of 34–36 weeks (gestational ages of 10–12 and 30–34 weeks are also mentioned).
Additionally, rapid testing may be performed in the maternity ward upon admission for delivery.
What methods are used to prevent intrapartum HIV transmission during labor?
The following are used to prevent intrapartum HIV transmission:
- Chemoprophylaxis during labor: performed to prevent mother-to-child transmission of HIV.
- Scheduled cesarean section: performed to prevent mother-to-child transmission of HIV in the presence of at least one of the conditions: HIV viral load > 1,000 copies/ml in the latest test before delivery, lack of viral load test results before delivery, absence of ART during pregnancy, or inability to administer ART during labor.
If chemoprophylaxis during labor is impossible, cesarean section acts as an independent prophylactic procedure. Performing a cesarean section for HIV prevention is not recommended if the duration of membrane rupture exceeds 4 hours.
What does postnatal prevention of HIV infection in a newborn consist of?
Postnatal prevention of HIV infection in a newborn includes two main components.
- Drug prophylaxis: administration of the third stage of chemoprophylaxis to the newborn.
- Nutrition: categorical exclusion of breastfeeding (use of formula feeding) due to the high risk of virus transmission via breast milk.
Class and exam questions
Why is the HIV test positive at birth in a child born to an infected mother?
This is due to the transplacental transfer of maternal immunoglobulins (IgG). A positive test in the first months of life reflects the mother's status, rather than the fact of the infant's infection.
When can a child born to an HIV-positive mother be deregistered?
A definitive serological diagnosis based on the absence of antibodies is established 1.5 years (18 months) after birth, when maternal antibodies are completely degraded in the child's bloodstream.
Which method allows the detection of HIV in a newborn at early stages?
The use of molecular genetic methods (PCR) is critically important for newborns, as they detect the genetic material of the virus itself (RNA or DNA), bypassing the presence of maternal antibodies.
What else to study on this topic
- Standard algorithm for immunological diagnostics in the Russian Federation (ELISA and Western blot)
- Interpretation of Western blot results (positive, negative, indeterminate)
- Clinical criteria and markers for suspecting HIV infection
- Viral load assessment by PCR
- Differential diagnostics of acute HIV infection stage
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