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In light of the fact that the number of HIV-infected women increases every year, it may seem that the number of newborns contracting the virus should also increase. But HIV in infants has reached such a low rate in the United States that many experts hope to see its presence in newborns eradicated.

HIV – which in its fully developed form becomes AIDS – infected 1,000 to 2,000 infants each year in the early 1990s, reflecting the virus’s approximate 25 percent rate of transmission from an infected mother to her child, according to the Center for Disease Control and Prevention. In some countries, this rate is as high as one in three births. Currently, it is estimated that the U.S. rate is only 2 percent.

So why has there been such a dramatic drop in perinatal HIV transmission? Dr. Paul Krogstad of the UCLA AIDS Institute says “the answer is that we are seeing better obstetrical care, and improvement of treatment of the virus in mothers, and improved knowledge of how to treat babies after delivery.”

By engaging in a multi-pronged approach to HIV prevention in an infant’s perinatal stage – five months before a child’s birth and one month afterward – doctors nationwide are effectively limiting the virus’s passage from mother to child.

In particular, the application of the drug Zidovudine has been a crucial component to the success of this approach. Zidovudine slows the progression of HIV into AIDS.

Krogstad explained that because of what is now known about the transmission of HIV from a pregnant woman to her child, certain vital steps are taken during pregnancy to minimize risk of infection.

When a woman’s pregnancy is confirmed by her doctor, he most often offers her an HIV test – in some states one must be offered by law, including California.

If the woman is found to be HIV-positive, additional tests are performed to evaluate the progression of the disease so that treatment for her can be considered. While there is no cure yet for HIV, current drugs can slow its progression to AIDS, which is fatal, and preventing this progression is key to keeping it from being passed from mother to child.

The expectant mother then receives Zidovudine and other drugs beginning in her second trimester, and is given the drug intravenously during pregnancy. A cesarean section birth also reduces the risk of infection.

Finally, the infant is given Zidovudine for the first six weeks after its birth and is closely monitored for signs of the virus.

Krogstad added that while “it’s still not clear whether or not a woman is going to transmit the virus if you did nothing,” these are the best means as of yet to lower the risk that a child will be born with HIV.

Krogstad also noted that “Zidovudine has been used apparently with great safety over the past 13 years,” but is now more effective as it is paired with other treatments.

Zidovudine works as a nucleoside reverse transcriptase inhibitor, meaning it prevents HIV from reproducing itself in infected antibody cells. Since retroviruses like HIV are reliant on using the replication tools of their hosts cells for propagation, preventing them from creating more virus DNA slows their spread. It does not eliminate the virus.

When an infant is developing, it has its mother’s antibodies, and will test as infected while still in the womb. After birth it acquires its own antibodies – which are not infected – and it becomes essential to use Zidovudine to suppress the virus in the mother’s antibodies as they are being phased out of the child’s body.

UCLA research has been integral in the development of new approaches to controlling AIDS. UCLA researcher Yvonne Bryson participated in the initial Zidovudine trials in the 1980s and 1990s, which led to its rapid approval by the Food and Drug Administration.

In 1991, the UCLA AIDS Institute was founded as a federally sponsored research facility through the National Institutes of Health with the goal of uniting medical scientists from a variety of specializations to focus on containing the AIDS epidemic.