HIV Infection Prevention From Parent to Child : Vertical Transmission

4th Pediatric Infectious Diseases Conference

ISSN 0973 - 0958

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Results

PREVENTION OF PARENT TO CHILD TRANSMISSION OF HIV INFECTION

HIV Infection Prevention From Parent to Child Transmission

Magnitude of Problem and Factors Affecting Vertical Transmission Efficacy

Related topics

Timing of Vertical Transmission and Phases of PTCT Prevention

Interventions To Decrease PTCT Transmission

Dr. Nitin Shah
Hon. Pediatrician- UHC, LTMG Hospital, Mumbai.
Treasurer, Indian Academy of Pediatrics, 1998-2001

Dr. M.R.Lokeshwar
Hon. Pediatrician, U.H.C., LTMG Hospital, Mumbai
and P.D. Hinduja National Hospital, Mumbai
Consultant Pediatric Hematologist-Oncologist, Lilavati Hospital, Mumbai.

Magnitude of Problem

World over 30-40 million people are expected to be HIV infected, which means 1 in 250 persons is HIV infected. Everyday 8000 new cases of HIV are expected to occur. 90% of HIV cases are in developing countries. In India the estimate is 3-5 million cases of HIV infections.

HIV cases are in women of childbearing age and 10-15% of cases occur in pediatric age group. It is estimated that daily 2000 new pediatric HIV cases occur world over, of which 200 cases occur in India. States with > 1% prevalence, i.e. high prevalence, of HIV amongst ANC mothers include Maharashtra, Andhra Pradesh, Tamilnadu, Karnataka and Manipur. States with 0.5% - 1% prevalence, i.e. intermediate prevalence are Gujarat, West Bengal and Nagaland. Rest of the states have < 0.5% prevalence.

Of the 28 million deliveries occurring in India annually, 1.4- 2.8 lakh deliveries occur in HIV positive mothers at a national average of 0.5 - 1% prevalence of HIV in ANC mothers. Without any interventions, of this 30% of babies will become HIV infected i.e. annually 42,000 - 84,000 babies get HIV infected in India vertically every year.

Efficacy of vertical transmission

Vertical transmission occurs due to infection of baby by maternal blood, cervico-vaginal secretion or via breast milk. The baby gets infected either due to transplacental hemorrhage or due to infection via umbilical cord or via oral and GI mucosa while swallowing infected amniotic fluid. The incidence of vertical transmission is 20% in western world whereas it is as high as 30-40% in developing countries. In India it is proved to be 30%. With the use of interventions like elective LSCS, anti-retroviral drugs and replacement feeding instead of breast-feeding, the incidence of transmission has dropped from 20% to 8% or even less than that in western world.

Factors that affect the efficacy of vertical transmission

There are various factors on which depends the efficacy of vertical transmission. These include maternal factors, type of delivery, factors in newborn, breast feeding and the type of interventions used to decrease the rate of transmission.

Maternal factors
Vertical transmission rate is high where mother has recently seroconverted or in those who are in late stage of HIV disease as both are likely to have high viral load. More the viral load in mother, more is the rate of vertical transmission. Except one study all other studies have shown that transmission does occur even when maternal viral load is low or is undetectable. Hence no level of viral load is safe as far as vertical transmission is concerned. Presence of high titers of anti-HIV antibodies in mother protects the newborn from HIV infection to some extent, as these antibodies pass transplacentally to the baby. Many studies have shown higher chances of vertical transmission when mothers were malnourished as they have low anti-HIV antibody levels. Vitamin A deficiency in mother is also associated with increased chances of vertical transmission. Presence of other STDs especially with bleeding lesions on cervix or vagina lead to increased chances of contamination of birth canal and increased chances of vertical transmission. Some viral characteristics, like highly replicating virus in mother, are associated with increased vertical transmission. In west mothers who used illicit IV drugs are known to have increased vertical transmission.
Type of delivery
Infected vaginal and cervical secretions as well as the maternal blood have been the source of HIV infections for the baby. HIV has been isolated from vaginal as well as cervical secretions of at least 50% of HIV infected women. Logically more is the length of time for which baby remains in contact with birth canal, more will be the chances of HIV infection. Various studies have shown increased vertical transmission rates in babies delivered vaginally, especially with prolonged labor and rupture of membrane for more than 4 hours. It is also more in presence of chorioamnionitis, traumatic delivery, instrumentation during delivery and episiotomy. In mothers with STDs the risk is more due to increased contamination due to open bleeding lesions. The incidence of transmission has been shown to be 25% with rupture of membrane > 4 hrs as compared to 14% with rupture of membrane <4 hrs. This has prompted many to study the effect of elective LSCS on HIV transmission as discussed later.
Preterm baby
Prematurity is associated with increased rate of vertical transmission probably related to thin skin, susceptible mucous membranes and immature immune functions with less transfer of maternal antibodies transplacentally before 34 weeks of gestation.
Postnatal factors
The main post-natal factor is breast milk which is expected to lead to 14% extra milk risk over and above other factors as discussed later.