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Human immunodeficiency virus (HIV) is a virus that suppresses the human immune system by attacking particular white blood cells (WBC) called CD4 lymphocytes, or CD4 T-lymphocytes. It can take several years from the time of infection for immunity to be suppressed enough to cause problems. If the infection is not discovered and treated, however, the immune suppression reaches an advanced stage called acquired immunodeficiency syndrome (AIDS). AIDS is characterized by extreme susceptibility to potentially fatal infections and it can happen in pregnancy, though it can be prevented. About 90.6 out of every 100,000 women are infected with HIV in the United States. African Americans are affected disproportionately, but another major factor is age. Based on studies published in 2019, HIV infection most commonly strikes those ages 25 to 29 years. AIDS itself, however, strikes first in the 30 to 34 year age group, followed by the 45 to 49 year age group. Although HIV spreads most notoriously through male-to-male sexual contact, it also can spread to females both sexually and through body fluid contamination, including blood (as may happen in a needle stick).
HIV is categorized into two subtypes: HIV-1 and HIV2. HIV-1 occurs throughout the world and is the most common subtype in North America. HIV-2 affects people mostly in West Africa. All types of HIV are retroviruses. This means that the viral genes, which the virus carries in the form of RNA, can become incorporated into the DNA of cells that the virus infects. This makes it very challenging to fight the infection. In terms of the severity of disease, HIV infection is classified as stage 0, 1, 2, or 3, with stage 0 being an early infection, stage 3 corresponding to AIDS, and stages 1 and 2 being intermediate.
For pregnant women infected with HIV, the number one goal is to prevent AIDS in the mother and also to prevent the virus from infecting fetus or newborn. The particular stages are defined based on the number of CD4 T-lymphocytes in blood samples, but the amount of actual virus particles in the mother’s blood and other maternal body fluids has a major impact on how protected the fetus is.
HIV is diagnosed purely with blood tests. In some countries and communities, pregnant women are screened routinely with one type of blood test. In other locations, they are tested, only if thought to be at high risk for contracting HIV, if there is a history of infections, or if their occupation puts them at risk. Healthcare work in particular carries a major risk. An initial type of blood test performed is an enzyme-linked immunosorbent assay (ELISA). This test is useful as a screen and is the first test performed, because it is quick, fairly inexpensive, and has an extremely low rate of false negative results (an apparently negative result in a person who is actually positive). This means that the test is unlikely to miss a person who has been infected with HIV, so if your ELISA comes out negative, you really are negative for the virus. The flip side of the coin is that this test can more easily produce a false positive result, but that’s okay for a screening test. Anyone whose ELISA test comes out positive then has her blood tested again with a different HIV test called a Western blot. This test is more complex and more expensive, but is more specific for HIV infection compared with the ELISA test. If this too is positive, then HIV infection is likely and many more tests are conducted. These tests include HIV RNA by polymerase chain reaction (PCR), a CD4 count, testing of the genetics of the HIV strain that you carry, basic blood tests, tests of urine samples, tests for hepatitis B and C viruses, tests for cytomegalovirus (CMV), human papilloma virus (HPV), and varicella-zoster virus, tests for tuberculosis and parasites, and tests for several sexually-transmitted infections.
For mothers-to-be who are HIV-positive without having AIDS, the risk of infection to the fetus is about 2 percent, but this risk can be decreased through the use of anti-HIV medications, so let’s turn to those next. Generally, doctors use four different drugs that attack the HIV virus in different ways. This can sound scary for a mother-to-be, but when everything is considered, the risk of not taking medications is many times worse for you, and the baby, compared with the risk of taking medications. HIV medications are categorized based on their mechanism of action as follows (the most important are bolded):
- Reverse transcriptase inhibitors (RTIs): These medicines block an enzyme from the virus that allows the virus’ RNA genes to be written out as DNA genes. Consequently, the medications prevent the infection from hiding in the person’s cells. RTIs are further categorized as:
- Nucleoside RTIs
- Non-nucleoside RTIs
- Protease inhibitors: These are medicines that block enzymes that are needed to break down various proteins. As a consequence, the virus has trouble reproducing itself.
- Integrase inhibitors: these medicines block an enzyme that is needed for inserting viral genes (that have been written out as DNA) into the DNA of an infected cell.
- Entry inhibitors: These medicines stop the HIV virus from entering human cells
If a pregnant female patient is merely exposed to HIV, but her tests show that an infection is not developing in her, she can be put on a single medicine for the sake of prevention against HIV infection. Such a patient must be monitored frequently with blood tests to see whether or not the infection develops. If an infection does develop, the patient would be put onto a regime of multiple drugs, consisting of both subtypes of RTI and also a protease inhibitor. With very aggressive drug treatment and monitoring, it’s possible to keep an HIV infection in check for decades so that the person does not develop AIDS. While more drug combinations and regimens are available to fight HIV in non-pregnant people, different drugs can be switched in and out of the combination regime and there are some combinations that are considered safe for the fetus and the mother. This means that the risk of not using them are higher than the risk of using them. The main controversy about HIV medications during pregnancy is whether they should be given during the first trimester. Typically, the risk of infection to the newborn can be reduced by delivering through a cesarean section, instead of vaginally. However, the level of risk and the need for cesarean section depends on the viral load in your blood.