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.
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.
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 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.”
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