AIDS and maternal-fetal transmission: a third of the contamination is in the last quarter

In pregnant and tested positive for the AIDS virus (HIV) women, the risk of transmission from mother to child predominates in late pregnancy, one third of infections occurring in the last quarter and two thirds during childbirth reveals an article in "Protocols"
Critical periods of pregnancy
However, contamination during the first weeks of pregnancy is possible, but seems rather associated with early miscarriages.

As to that observed during the second quarter, it remains outstanding. The second period is the risk of contamination of breastfeeding.

If no preventive measures are taken, the rate of transmission of HIV from mother to child is estimated between 20 and 25% for HIV-1 and of the order of 1 to 4% for HIV-2 . It rises to 10% if breastfeeding or 15% if it is extended and no action is taken.

During pregnancy, HIV exposure occurs through the placenta or during mucosal exposure by maternal blood, amniotic fluid or genital secretions may contain viral particles can access the uterine cavity. The preponderance of contamination at the time of delivery reflects exposure to genital secretions or maternal blood during passage of the newborn in the birth canal.

The placenta, leading to the contamination
The placenta is essential for the growth and survival of the fetus and is a physical and immunological barrier protecting. Cells that compose it are contiguous, thereby preventing the passage therebetween of the viral particles of HIV. This is no longer the case if it is damaged by infections or childbirth where microtransfusions may occur.

In fact, labor and contractions cause small areas of placental abruption become very thin and therefore more fragile at this stage. These microlesions allow the passage of small amounts of maternal blood infected or infected cells.

Infection of cells forming the placenta itself, called trophoblasts, is also possible and would explain the contamination occurring before delivery. In fact, very early in embryonic development, these cells separate the embryo from the mother cell to form two layers, one of which will bathe in the maternal circulation. Trophoblasts can therefore directly meet the HIV and the latter into the cell.

Of known risk factors
Risk factors of HIV transmission from mother to child are of different types. First, the immunovirological parameters of the mother, as the clinical manifestations of AIDS, a decrease in CD4 cell count and viral load.

A high viral load before birth is indeed associated with increased transmission rates. For example, an increase of a factor of ten of this charge - the last determined before birth - increases the transmission rate by 2.4.

Other risk factors: the existence of associated diseases and sexually transmitted diseases. Furthermore, amniocentesis or amniocentesis, which requires an invasive procedure, increase the risk of transmission if no preventive treatment is applied. Similarly, certain practices or circumstances of birth play in the transmission of HIV from mother to child, such as premature labor or premature rupture of membranes.

Finally, unprotected heterosexual intercourse during pregnancy with an infected partner, and frequent vaginal intercourse, can promote the accumulation of virus from the ejaculate in the birth canal.

For breastfeeding, the presence of virus in milk, breastfeeding duration, seroconversion during this period, inflammation or lesions of the breast, pregnancy at an early age, a small number of pregnancies and the child, the existence of candidiasis are many risk factors for contamination.