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Spreading of HIV infection. Pregnancy Effects on HIV. Effect of HIV infection on pregnancy.
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Spreading of HIV infection
HIV is spread through contact with certain body fluids from a person with HIV. These body fluids include:
· blood
· semen
· pre-seminal fluid
· vaginal fluids
· rectal fluids
· breast milk
Thus, ways of Contamination are:
· sexual
· parenteral
· vertical (from mother to baby during pregnancy, labor, breast feeding)
· surgical (during invasive procedures: operations, manicure, etc. ) (5-10%)
The spread of HIV from person to person is called HIV transmission.
Diagnosis of HIV
All pregnant women should be offered HIV testing, with appropriate pre- and post-test counselling, as part of their routine prenatal care in each pregnancy. This testing should be repeated in each trimester in women who are recognized to be at high and ongoing risk for HIV infection. The HIV test is based on detection of antibodies, most often by an antibody capture–enzyme-linked immunosorbent assay (ELISA). A positive result is always confirmed by other laboratory tests on the same sample using different methods to detect HIV antibodies (e. g. particle agglutination assays and Western blotting) and by repeating the HIV antibody detection tests on a second sample of blood. The ELISA uses antigens prepared by lysis of whole virus, recombinant and/or synthetic peptides. The sensitivity and specificity of the tests are dictated by these preparations. Currently used ELISA reagents are generally recombinant antigens that improve specificity and reduce the window period compared with earlier preparations, but about 30% of infections with HIV-2 are falsely negative. The window period is the time delay from infection to positive ELISA averages 10 to 14 days with newer test reagents. The ELISA screening test requires a " repeatedly reactive" test, which is the criterion for Western blotting (WB) testing. For the Western blot, specific viral proteins are separated by electrophoresis, and reaction of antibody to 3 proteins must occur for the test to be considered positive. Indeterminate results occur when 1 or 2 of the proteins are present. In low-risk populations, indeterminate results usually revert to negative over several months. WB testing should always be coupled with ELISA screening; WB alone has a 2% rate of false positives.
The disease can be determined by measuring the level of CD4 lymphocytes in peripheral blood. A normal level is > 0. 5/l (500/mm3). There is a 10 % risk of AIDS developing within one year when the CD4 lymphocytes count drops to 0. 2/l. This is the level at which primary prophylaxis against Pneumocystis carinii pneumonia (PCP) is recommended.
The concentration of viral ribonucleic acid (RNA) should also be measured in the plasma. A high level, > 100, 000 particles/ml predicts rapid disease development, whilst a low level, < 10, 000 HIV viral load copies/ml is associated with a low risk of disease progression.
Blood counts and viral load. For pregnant women infected with HIV, in addition to the standard prenatal assessment, continued assessment of HIV status is important. A complete blood count to assess anemia and white blood cell count as well as renal and liver function tests should be included. Initial evaluation includes CD4+counts, which help determine the degree of immunodeficiency.
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Pregnancy Effects on HIV
In pregnancy, immune function is suppressed in both HIV-infected and uninfected women. There is a decrease in immunoglobulin, reduced complement levels in early pregnancy and a more significant decrease in cell-mediated immunity during pregnancy. These normal changes during pregnancy have led to concern that the effect of pregnancy in HIV disease could be to accelerate the progression of the infection. Early reports of pregnancy in HIV-infected women seemed to support this. Prospective follow-up studies have not confirmed these findings to date. In all women, the absolute CD4 count decreases no matter whether HIV-positive or negative (pregnancy does not make HIV worse). In HIV-positive women, percentage of CD4 cells should not change and viral load should not change because of pregnancy.
Effect of HIV infection on pregnancy.
HIV infection has been reported to have little effect on pregnancy outcome or complications. Adverse pregnancy outcomes have, however, been reported including complications of both early and late pregnancy. HIV-1 and HIV-2 infection have both been linked to a higher rate of spontaneous misscarriage. More than half of these aborted fetuses had evidence of HIV infection, particularly with the thymus gland affected. Preterm labour may be more common in HIV-positive women, with rates as high as double those rates seen in uninfected women in some reports. Preterm rupture of membranes and abruptio placentae may also be increased in HIV-positive women. Higher rates of ectopic pregnancy have been reported in HIV-positive women than in uninfected women, which may be related to the effects of other concurrent sexually transmitted diseases. Genital tract infections such as Neisseria gonorrhoea, Chlamydia trachomatis, Candida albicans and Trichomonas vaginalis infection have been reported to be more common in women with HIV. Syphilis is one of the most common in HIV-positive women. Bacterial pneumonia, urinary tract infections and other infections are common during pregnancy in HIV seropositive women. In addition to these infections and parasitic infestations, any of the HIV-related opportunistic infections can be found during pregnancy. Tuberculosis is the commonest opportunistic infection associated with HIV in the developing world, and particular attention should be paid to its diagnosis in pregnant HIV-positive women. Herpes zoster is common in young HIV-positive women, although uncommon in this age group in the absence of HIV infection. Kaposi’s sarcoma has been reported during pregnancy in HIV-positive women. HIV seropositivity was associated with a decrease in birth weight, but this was less than the drop attributable to smoking. Increased stillbirth rates have been reported, especially from areas where the epidemic has been present for a long time. And the risk is lower in asymptomatic women. Infectious complications are also more common during the postpartum period in HIV-positive women. Cesarean section is particularly associated with higher infectious morbidity, especially in women with low CD4+ counts, and an increased mortality.
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Pregnancy against HIV infection in the mother is fraught with transmission of infection to the fetus. The spread of HIV from a woman with HIV to her child during pregnancy, childbirth, or breastfeeding is called mother-to-child transmission of HIV (MTCT). Mother-to-child transmission is the most common way that children become infected with HIV. Although mother-to-child transmission of HIV-2 has been documented, this occurs less frequently than with HIV-1.
Thus, the course of pregnancy in HIV-infected women is associated with increased raytes of:
• Abortions.
• Prematurity.
• IUGR.
• Maternal and perinatal morbidity and mortality.
• Perinatal transmission
Perinatal Transmission
In most cases, HIV will not cross through the placenta from mother to baby. If the mother is healthy in other aspects, the placenta helps provide protection for the developing infant. Factors that could reduce the protective ability of the placenta include in-uterine infections, a recent HIV infection, advanced HIV infection or malnutrition. Pregnancy appears to have little effect on the progress of disease in asymptomatic HIV-positive women or in those with early infection, although there may be more rapid progression in women with late stage HIV disease
Perinatal transmission rates of HIV in the absence of antiretroviral prophylaxis range from 14% to 33% in industrialized nations. In Africa, rates up to 43% have been reported.
Transmission of HIV-1 can occur in-utero, at the time of labour and delivery, or postnatally through breastfeeding. Exposure of the fetus to the virus in cervico-vaginal secretions is thought to play a role. In addition, recent reports have indicated that mode of delivery may affect the transmission rate. Cesarean section whether elective or emergency has been shown to decrease transmission in some studies and prolonged rupture of membranes [more than four hours] to increase the risk of transmission.
Data support HIV transmission during the intrauterine, intrapartum, and postpartum periods.
· Intrauterine transmission of HIV is most likely transplacental. Transmission later in pregnancy is more likely to be preventable with antiretroviral agents. Overall, 20–30% of perinatal transmission probably occurs in the intrauterine period.
· Intrapartum transmission, which accounts for up to 80% of perinatal transmission, may occur by transplacental maternal-fetal transfusion of blood during uterine contractions or by exposure to infected maternal blood and cervicovaginal secretions.
· Postpartum transmission. Breast feeding is the primary mechanism of postnatal transmission. HIV has been isolated from cellular and noncellular fractions of breast milk.
All those types of transmission (from mother to fetus) are called vertical transmission. The risk of vertical transmission is proportional to the maternal viral load (concentration of virus in maternal plasma).
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