HIV/AIDS Syndrome - Infectious Diseases in Pregnancy

HIV/AIDS SYNDROME

Worldwide, women account for nearly 50% of those in-fected with HIV. The CDC estimates that 27% of those living with acquired immune deficiency syndrome (AIDS) in the United States are women. Of these women, 71% were exposed through heterosexual contact and 27% through injection drug use. One percent of those living with AIDS are children under the age of 13, most of whom acquired the infection perinatally.

The usual estimated latency period from untreated HIV to AIDS is about 11 years. HIV infection becomes AIDS as thehelper (CD4 ⁺) lymphocyte count decreases and the host becomes more susceptible to other types of infections. With the availability of increasingly effective antiretrovi-ral drugs, life span and quality of life have improved dra-matically. 

Pathophysiology

HIV is a single-stranded, RNA, enveloped human retrovirus that has the ability to become incorporated into the cellular DNA of CD4⁺ cells such as lymphocytes, monocytes, and some neural cells. Once infected, seroconversion usually oc-curs within 2 to 8 weeks, but it may take up to 3 months and in rare cases, 6 months. HIV infection appears to have no direct effect on pregnancy course or outcome. Likewise, pregnancy does not seem to affect the course of HIV. BothHIV and pregnancy may affect the natural history, presentation, treatment, or significance of certain infections, and these, in turn, may be associated with pregnancy complications or perinatal in-fection. These infections include vulvovaginal candidiasis,bacterial vaginosis, genital herpes simplex, human papillo-mavirus (HPV), syphilis, cytomegalovirus (CMV), toxoplas-mosis, and hepatitis B and C. All women demonstrate a decline in absolute CD4⁺ cell counts in pregnancy, which is thought to be secondary to hemodilution. On the other hand, the percentage of CD4⁺ cells remains relatively stable. Therefore, percentage, rather than absolute number, of CD4⁺ cells may be a more accurate measure of immune function for HIV-infected women.

The baseline rate of perinatal HIV transmission with-out prophylactic therapy is approximately 25%, and is gen-erally related to higher viral loads and lower CD4⁺ counts. With zidovudine (ZDV) monotherapy, perinatal transmission is reduced to ∼8%. Currently, with combination antiretroviral therapy and an undetectable viral load, perinatal transmission is reduced to 1% to 2%. There is evidence that transmissioncan occur antepartum, intrapartum, or postpartum through breastfeeding; however, 66% to 75% of transmission appears to occur during or close to the intrapartum period, particularly in non-breastfeeding populations.

Screening and Testing

Initial screening consists of enzyme-linked immuno-sorbent assay (ELISA), which is based on an antigen–antibody reaction. In 99% of cases, antibodies to HIV be-come detectable by 3 months after infection. If results of ELISA are positive, a Western blot test, which identifies antibodies to specific portions of the virus, is performed to confirm the diagnosis. A serologic test is reported as pos-itive only if both the ELISA and the Western blot analy-ses are positive; this testing has a sensitivity and specificity of over 99%.

Universal, voluntary HIV screening for pregnant women is standard and should be part of the standard prenatal laboratory tests, unless a patient states that she does not want HIV testing. This “opt-out” approach is recommended by both ACOG and the CDC; however, state and local laws to the contrary may supersede these recommendations.

Refusal of testing should be documented.

Additionally, third-trimester repeat screening is recom-mended for at-risk populations (including women with an STD or women who use illicit drugs, exchange sex for money or drugs, have multiple sexual partners in preg-nancy, or who have signs or symptoms suggesting acute HIV during pregnancy), as well as for women who de-clined testing in the first trimester or have undocumented HIV status at the time of labor and delivery.

Rapid HIV testing is a valuable alternative to the con-ventional testing previously discussed. Results can be avail-able within hours after the blood sample is obtained, and thus is especially useful when a patient of unknown HIV status presents in labor.

A positive rapid HIV test must be confirmed by Western blot analysis or immunofluorescence assay before the woman is deemed HIV positive; however, immediate antiretroviral treatment should be started as soon as a rapid HIV-positive result is noted in a laboring patient

Management

Management involves antiretroviral therapy and taking pre-cautions during delivery to avoid transmission.

Antiretroviral therapy in pregnancy is a key component to reduction of perinatal transmission to as low as 1% to 2%.

Effective combination antiretroviral therapy should be of-fered to all HIV-infected pregnant women, and is admin-istered in the antepartum and intrapartum period as well as to the neonate. Other than maternal disease status and viral load, risks factors for increased vertical transmission of HIV include chorioamnionitis, prolonged rupture of mem-branes, invasive fetal monitoring, and mode of delivery.

Awareness of maternal HIV status can help guide management of labor and delivery to minimize risk of transmission to the fetus. The likelihood of transmission increases linearly with increasing duration of rupture of membranes. The use of fetal scalp electrodes or fetal scalp sampling increases exposure of the fetus to maternal blood and genital secretions, and may increase the risk of vertical transmission, depending on the serum and genital HIV viral load. These techniques should be avoided. Use of epi-siotomy or vacuum extraction or forceps may potentially increase risk of transmission by increasing exposure to ma-ternal blood and genital secretions. However, these tech-niques may help shorten duration of labor or rupture of membranes with vaginal delivery and, thus, may decrease the likelihood of transmission. Finally, cesarean delivery performed before the onset of labor and rupture of mem-branes significantly reduces the risk of perinatal HIV trans-mission. Planned cesarean delivery at 38 weeks of gestation to prevent perinatal transmission of HIV is recommended for women who have a viral load >1000 copies/mL.

Breastfeeding plays a significant role in perinatal HIV transmission; it is estimated to have accounted for up to50% of newly infected children globally. Breastfeeding in the setting of established maternal infection has a signifi-cant additional risk of transmission.

When safe alternatives are available, breastfeeding should be avoided in HIV infection.

The field of HIV care and management is rapidly ad-vancing and care of HIV-infected pregnant women should be coordinated with a health care provider who regularly cares for HIV-infected women. Comprehensive informa-tion is also provided and regularly updated on the U.S. Department of Health and Human Resources Web site AIDSinfo, at www. aidsinfo .nih.gov, under “perinatal treat-ment guidelines.”