Preventing perinatal transmission of HIV: Your vigilance can pay off

The Centers for Disease Control and Prevention (CDC) recommends routine voluntary screening for HIV as a standard part of basic medical care.¹⁴ This is particularly important among higher-risk populations. Family physicians could offer a full range of family planning options for women who choose to undergo screening or otherwise test positive for HIV.

Preventing HIV transmission from mother to infant
As many as 40% of HIV-infected infants in the United States are born to mothers unaware of their HIV status at delivery.¹⁵ The CDC emphasizes that it is never too late for pregnant women to be tested, and recommends an “opt out” approach, thereby establishing HIV testing as a routine part of prenatal care.¹⁴ Recommendations also include repeating the HIV screen in the third trimester for women who meet certain criteria (TABLE 1);¹⁴ antiretrovirals given to a mother during labor and to the infant after birth can still significantly reduce the risk of perinatal transmission.¹⁶ Accordingly, the use of rapid HIV tests in delivery rooms is recommended for women with unclear HIV status.¹⁵ US guidelines also cover scenarios in which maternal HIV infection is first realized during labor or after a child has been born.¹

Women known to be living with HIV who wish to become pregnant can be assured that, if current US guidelines are followed, the risk of HIV transmission to their infant is less than 2%.¹ These guidelines include detailed recommendations for antiretroviral drug use by pregnant HIV-infected women that vary by clinical scenario. The guidelines are updated frequently and are available at https://aidsinfo.nih.gov/contentfiles/PerinatalGL.pdf.¹ The full package of interventions also includes obstetric measures and a course of ZDV administered to the infant after birth.

Antiretrovirals during pregnancy. Pediatric AIDS Clinical Trials Group Protocol 076 (PACTG 076) was the first major study of antiretroviral use for perinatal transmission prevention.¹⁷ This randomized, placebo-controlled study evaluated antiretroviral prophylaxis with ZDV monotherapy. ZDV was given to mothers orally, beginning at 14 to 34 weeks of pregnancy, and intravenously during labor and delivery, and to newborns orally for the first 6 weeks of life. Infants were formula fed. At 18 months, HIV transmission occurred with 25.5% of women receiving placebo and 8.3% of women receiving ZDV—a 67.5% relative risk reduction.¹⁷

Subsequently, it was realized that antiretroviral regimens that use 3 medications are superior to those that use only 1 or 2.¹⁸ Current standard of care in the United States is use of a 3-drug combination during pregnancy (known as highly active antiretroviral therapy, or HAART).¹ HAART generally comprises 2 nucleoside reverse transcriptase inhibitors (ZDV, lamivudine) and either a non-nucleoside reverse transcriptase inhibitor (nevirapine) or a protease inhibitor (lopinavir/ritonavir).

Some women meet criteria for HAART based on their clinical or immunologic status (history of an AIDS-defining condition or severe HIV-associated symptoms, or a CD4+ count <350 cells/mm³, respectively). However, all pregnant women should be offered HAART, regardless of their immunologic or virologic status, as perinatal transmission may occur even at very low or undetectable viral loads.¹ HIV antiretroviral resistance should be assessed before initiating HAART.¹

A woman’s primary care and obstetric providers are important to the success of antepartum antiretroviral therapy, even though they may not directly manage the regimen. The goal of therapy is an undetectable maternal viral load at delivery,¹ an achievement that depends in large part on adherence to antiretroviral therapy,¹⁹ which may be influenced by the degree to which coordinated care is delivered.²⁰

Obstetric interventions. Compared with vaginal delivery, cesarean delivery reduces perinatal HIV transmission.^21,22 To be most effective, a cesarean section must be performed electively, before membranes rupture.¹² For most HIV-infected women, cesarean section is as safe as it is for HIV-negative women. For women with advanced disease or AIDS, cesarean section may carry a higher risk of maternal complications.²³

For women with unknown HIV RNA levels (viral load) or a viral load >1000 copies/mL near the time of delivery, US guidelines recommend that scheduled cesarean delivery be performed at 38 weeks’ gestation, whether or not they are receiving antepartum antiretroviral drugs.¹² For women taking antiretrovirals who have a viral load of <1000 copies/mL, guidelines advise that data are insufficient to evaluate the potential benefit of cesarean delivery in preventing perinatal transmission.¹² When viral load is <1000 copies/mL, administration of intravenous ZDV followed by vaginal delivery (as in PACTG 076–2 mg/kg intravenous load over 1 hour, then 1 mg/kg per hour until delivery) is an option, and is commonly used in the United States.^1,23