Williams Manual of Pregnancy Complications, 23 ed.

CHAPTER 85. Human Immunodeficiency Virus

Worldwide it is estimated that there are 33 million infected persons with HIV/AIDS. In the United States through 2006, there are estimated to be 1.1 million infected individuals. In 2006, women accounted for 26 percent of all adults and adolescent HIV/AIDS cases. The incidence during pregnancy varies from 0.3 to 2 percent depending on the population studied.

ETIOLOGY

Causative agents of acquired immunodeficiency syndrome (AIDS) are DNA retroviruses termed human immunodeficiency viruses, HIV-1 and HIV-2. Most cases worldwide are caused by HIV-1 infection. Although HIV-2 infection is endemic in West Africa, it is uncommon in the United States.

Retroviruses have genomes that encode reverse transcriptase, which allows DNA to be transcribed from RNA. The virus thus can make DNA copies of its own genome in host cells. Transmission is similar to hepatitis B virus, and sexual intercourse is the major mode of transmission. The virus also is transmitted by blood or blood-contaminated products, and mothers may infect their infants.

CLINICAL PRESENTATION

Acute illness (acute retroviral syndrome) usually begins within days to weeks after exposure and is similar to many other viral syndromes, usually lasting less than 10 days. Common symptoms include fever and night sweats, fatigue, rash, headache, lymphadenopathy, pharyngitis, myalgias, arthralgias, nausea, vomiting, and diarrhea. Chronic viremia begins after symptoms abate. Stimuli that cause further progression from asymptomatic viremia to the immunodeficiency syndrome are unclear, but the median time is about 10 years.

When HIV-positivity is associated with any number of clinical findings, then AIDS is diagnosed. Generalized lymphadenopathy, oral hairy leukoplakia, aphthous ulcers, and thrombocytopenia are common. A number of opportunistic infections that may herald AIDS include esophageal or pulmonary candidiasis, persistent herpes simplex or zoster, condylomata acuminata, tuberculosis, cytomegalovirus infection, molluscum contagiosum, pneumocystis infection, toxoplasmosis, and others. Neurological disease is common, and about half of patients have central nervous system symptoms. A CD4+ count of less than 200/μL is also considered diagnostic for AIDS.

Serological Testing

The enzyme immunoassay (EIA) is used as a screening test for HIV antibodies. A repeated positive screening test has a sensitivity of over 99.5 percent. Confirmation is usually performed with either the Western blot or immunofluorescence assay. According to the CDC, antibody can be detected in 95 percent of patients within 1 month of infection; antibody serotesting does not exclude early infection. Early infection can be diagnosed using viral P24 core antigen or viral RNA or DNA. Women with undocumented HIV status at delivery should have a “rapid” HIV test performed and a positive result confirmed. Table 85-1 details a strategy for rapid testing.

TABLE 85-1. Strategy for Rapid HIV Testing of Pregnant Women in Labor

image

image

MATERNAL AND FETUS-INFANT INFECTION

Mother-to-infant transmission accounts for most HIV infections among children. Transplacental transmission can occur early, and the virus has been identified in pregnancies terminated by elective abortion. In most cases, however, transmission occurs in the peripartum period, and 15 to 40 percent of infants born to untreated HIV-infected mothers will be infected. Pregnancy complications, including preterm delivery, fetal growth restriction, and stillbirth, are related to maternal HIV infection.

A number of risk factors for fetus-infant transmission have been reported (Table 85-2). Plasma viral HIV-1 RNA levels have proven to be the best predictor of risk for transmission to the infant. A viral load of less than 1000 copies per milliliter is associated with the lowest risk of transmission, although no threshold has been identified below which transmission does not occur.

TABLE 85-2. Risk Factors Associated with Perinatal Vertical Transmission of HIV-1

image

MANAGEMENT OF HIV INFECTION

Antiretroviral therapy should be offered to all HIV-infected pregnant women to begin maternal treatment as well as to reduce the risk of perinatal transmission regardless of CD4+ T-cell count or HIV RNA level. There are now many approved antiretroviral agents (see Table 85-3). The US Public Health Task Force has issued guidelines that detail management of different scenarios during pregnancy. In all women, zidovudine is given intravenously during labor and delivery. The treatment regimens are increasing in complexity—current perinatal guidelines are updated frequently on the US Department of Health and Human Services AIDS information website (www.aidsinfo.nih.gov/guidelines). All women should have an HIV antiretroviral drug-resistance test performed prior to initiating therapy.

TABLE 85-3. Classes of Antiretroviral Drugs

image

image

image

Laboratory Evaluation

Measurements of T-lymphocyte counts and HIV-1 RNA levels should be performed as an adjunct to management approximately each trimester, or about every 3 to 4 months. These are used to make decisions to alter therapy, to direct route of delivery, or to begin prophylaxis for Pneumocystis carinii pneumonia. Testing for other sexually transmitted diseases and for tuberculosis is also done. One to two percent have been reported with the use of combination antiretroviral therapy (versus 10 to 28 percent if no therapy is used).

The American College of Obstetricians and Gynecologists (Scheduled cesarean delivery and prevention of vertical transmission of HIV infection. Committee Opinion No. 234, May 2000) has recommended scheduled cesarean delivery for HIV-infected women with an HIV-1 RNA load of more than 1000 copies/mL regardless of antiretroviral therapy. Scheduled delivery may be done as early as 38 weeks to lessen the chances of spontaneous membrane rupture or the onset of labor.

Breastfeeding increases the risk of neonatal transmission and, in general, is not recommended in HIV-positive women since approximately 16 percent of breastfed infants develop infection.

Prevention of HIV Transmission to Health-Care Providers

The CDC emphasizes that because the medical history and examination cannot identify reliably all patients infected with HIV or other blood-borne pathogens, blood and body-fluid precautions should be used consistently in all patients. Gloves, surgical masks, and protective eyewear (goggles) must be worn for all deliveries for protection against droplets, splashing of blood, or other body fluids. Fluid-resistant gowns should also be worn. Gloves and gowns should be used when handling the placenta or the infant. Mouth-suction devices for clearing the airway should be avoided. If a glove is torn or there is a needlestick or other injury, the glove should be removed and a new glove used as promptly as patient safety permits. The needle or instrument involved in the incident should also be removed from the sterile field.

For health-care workers exposed to contaminated fluids—for example, a needlestick injury—post exposure prophylaxis is recommended. Current recommendations are available at www.aidsinfo.nih.gov/guidelines.


For further reading in Williams Obstetrics, 23rd ed.,

see Chapter 59, “Sexually Transmitted Diseases.”