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Indian Journal of Dermatology, Venereology and Leprology
Medknow Publications on behalf of The Indian Association of Dermatologists, Venereologists and Leprologists (IADVL)
ISSN: 0378-6323 EISSN: 0973-3922
Vol. 74, Num. 3, 2008, pp. 200-207

Indian Journal of Dermatology, Venereology and Leprology, Vol. 74, No. 3, May-June, 2008, pp. 200-207

Seminar: HIV Infection

Prevention of mother-to-child transmission

Surjushe Amar, Maniar Janak

Department of Dermatology, Venereology and Leprosy, Shri Vasantrao Naik Government Medical College, Yavatmal, Maharashtra
Correspondence Address:Department of Dermatology, Venereology and Leprosy, Shri Vasantrao Naik Government Medical College, Yavatmal, Maharashtra - 445 001
dramarsurjushe@rediffmail.com

Code Number: dv08087

Introduction

Mother-to-child transmission (MTCT) is the most important source of human immunodeficiency virus (HIV) infection in children below the age of 15 years. It affects approximately 5,00,000 infants per year all over the world and is responsible for 1800 new infections in children daily, the majority of which are in developing countries. The rate of perinatal transmission is 15-25% in developed countries, and 25-45% in developing countries. [1] In India, the Joint Technical Mission (2006) estimated that out of 27 million annual pregnancies, 189,000 occur in HIV-positive, pregnant women. An estimated cohort of 56,700 infected babies will be born annually in the absence of any intervention. The most affected states are Andhra Pradesh, Karnataka, Maharashtra, Tamil Nadu, and Manipur. [2]

In 1994, the Pediatric AIDS Clinical Trials Group (PACTG) protocol 076 reported a decrease in the risk of MTCT by nearly 70% due to the administration of zidovudine (AZT) to women from the fourteenth week of pregnancy onwards and during labour, and to the newborn in the absence of breastfeeding. [3] In non-breastfeeding populations, this regimen along with elective caesarean section decreased the transmission rate to ≤2%. [4],[5] Similar low vertical transmission has resulted with the use of highly active antiretroviral therapy by pregnant women. [6] Still in resource-poor settings, the limitations for these regimens are the cost and complexity. The regimens should be cost-effective, easily approachable, with high efficacy and should cause no or lesser side effects without any risk of resistance.

In developing countries like India, it was believed that husbands were mostly responsible for transmission of HIV in mothers through the sexual route and therefore, they are considered to be equally responsible for the transmission of HIV to their children. In India therefore, PMTCT is termed as PPTCT (prevention of parent-to-child transmission) so that mothers alone should not be blamed for HIV in their children. In India, the PPTCT program was started in 2002. Currently, there are more than 4000 Integrated Counselling and Testing Centres (ICTCs) in the country, most of these in government hospitals, which offer PPTCT services to pregnant women.

Rate of Transmission of HIV from Mother to Infant

The rate of perinatal transmission without intervention is 19-36%. [7] Prenatal, intranatal and postnatal factors are responsible for MTCT. The rate varies in each scenario and these rates are important for the development of protective measures. Twenty-five to thirty-five per cent of total transmission occurs during the prenatal period, mainly in late pregnancy; [8] while 70-75% of total transmission occurs during the intranatal period. Postnatal transmission is via breast milk and accounts for 10-16% of all transmission. [9] The proposed mechanisms for intrapartum transmission are uterine contractions during labour that are responsible for micro-transfusion from constant massage of the placental bed and during labour exposure of the baby′s mucocutaneous surface to maternal blood and cervical secretions. As per the Pediatric Virology Committee of the AIDS Clinical Trials Group in the United States, a child with a positive PCR within 48 h of birth has been infected in utero and a child who is PCR-negative at 48 h but positive 7-90 days after delivery indicates an intrapartum infection. [10]

Factors Affecting Mother-to-Child HIV Transmission[1]
Mother-to-child transmission of HIV-1 is multifactorial. Factors responsible for mother-to-child can be divided into five categories: (1) maternal factors, (2) virological factors, (3) obstetric factors, (4) fetal factors and (5) infant factors [Table - 1]

Strategies for MTCT Prevention: [20]
The three-pronged approach to the prevention of MTCT is:

  1. Primary prevention of HIV among parents.
  2. Prevention of unwanted pregnancy in HIV-infected females
  3. Core interventions to prevent MTCT by HIV-positive mothers

Primary prevention of HIV infection includes HIV education; safe-sex practices; avoidance of intravenous drugs and sharing contaminated needles; prevention, diagnosis and early treatment of sexually transmitted diseases; change in moral behavior and attitude of the community. This is the only method that is 100% effective in preventing HIV transmission to infants.

Prevention of unwanted pregnancy in HIV-infected females, which is the most effective means of preventing MTCT, requires the provision of voluntary counseling testing (VCT) services and voluntary, safe, and effective contraception, sterilization, or pregnancy termination.

Core MTCT prevention intervention consists of compre-hensive maternal and child health services (antenatal, postnatal, and child health); voluntary counseling and testing (VCT), antiretroviral prophylaxis; counseling and support for safe infant feeding and optimal obstetrical practices. The major focus is on antiretroviral prophylaxis in this article.

Antiretroviral regimens for prophylaxis
Due to the success of the Pediatric AIDS Clinical Trials Group (PACTG) protocol 076, various regimens have been developed [Table 2a] and [Table 2b]. In India, National AIDS Control Organization (NACO) has started to implement the single-dose-of-nevirapine (NVP) program in all the states beginning with the states with a high prevalence of HIV after the success of the HIVNET-012 study. [21] PPTCT services cover about 10% of the pregnancies in the country and 2.1 million pregnant women accessed this service in 2001. Of these, more than 16,500 pregnant women were HIV-positive.

Recommendations for use of antiretroviral prophylaxis in various clinical situations [29]
The following four scenarios should be considered while discussing HIV during pregnancy:

Scenario 1: HIV-1-infected pregnant women who have not received prior antiretroviral therapy: Recommendation
Standard clinical, immunological, and virological evaluation should be carried out. Recommendations for initiation and choice of antiretroviral therapy should be based on the same parameters used for persons who are not pregnant, although the known and unknown risks and benefits of such therapy given during pregnancy must be considered and discussed. If the viral load is> 1000 c (copies)/mL HAART including the three-part AZT regimen of PACTG 706, should be started. If the viral load is < 1000 c/mL, HAART or only AZT may be given according to the PACTG 706 protocol [Table 2a]. In the first trimester of pregnancy, one may consider delaying the initiation of therapy until after 10-12 weeks′ gestation because the risks associated with various agents taken during organogenesis are largely unknown. [30]

Scenario 2: HIV-1-infected women receiving antiretroviral therapy during the current pregnancy: Recommendation
Women receiving antiretroviral therapy and whose pregnancy is recognized during the first trimester, should be counseled regarding the benefits and potential risks of antiretroviral administration during this period, and continuation of therapy should be considered. Women receiving antiretroviral therapy and whose pregnancy is identified after the first trimester, should continue therapy. AZT should be a component of the antenatal antiretroviral treatment regimen after the first trimester whenever possible, although this may not always be feasible. [31] If therapy is discontinued during the first trimester, all drugs should be stopped and reintroduced simultaneously to avoid the development of drug resistance. [32] In case of NNRTI based regimen, stop NNRTI and continue NRTIs for 3-7 days so as to prevent drug resistance. Regardless of the antepartum antiretroviral regimen, AZT administration is recommended during the intrapartum period and for the newborn.

Scenario 3: HIV-1-infected women in labor who have had no prior therapy: Recommendation
Several effective regimens are available for intrapartum therapy for women who have had no prior therapy [Table - 3]. If single-dose nevirapine is given to the mother, alone or in combination with AZT, consideration should be given to adding maternal AZT/3TC starting as soon as possible (intrapartum or immediately postpartum) and continuing for 3-7 days, which may reduce the development of resistance to nevirapine. In order to plan continuation of therapy, the mother should have appropriate assessments ( e.g ., CD4+ cell counts and HIV1 RNA copy number) in the immediate postpartum period.

Scenario 4: Infants born to mothers who have received no antiretroviral therapy during pregnancy or intrapartum: Recommendation
AZT should be initiated as soon as possible after delivery, preferably within 6-12 hours of birth as per the ACTG 076 protocol. Some clinicians use AZT in combination with other ARV drugs, particularly if a mother is suspected of having an AZT-resistant virus. [33],[34] Efficacy for infants is currently unknown. In the immediate postpartum period, the mother should have appropriate assessments ( e.g ., CD4+ cell counts and HIV1 RNA copy number) to determine whether antiretroviral therapy is recommended for herself. Early HIV diagnostic testing should be done on infants so that if he or she is HIV-1 infected, treatment can be initiated as soon as possible.

Special issues related to the transmission of HIV from mother to child
 Pre-conceptional counseling and care for HIV-1-infected women of childbearing age [35]
The Centers for Disease Control and Prevention (CDC), the American College of Obstetrics and Gynecology (ACOG), and other national organizations recommend offering preconception counseling and care as a component of routine primary medical care to all women of childbearing age. The purpose of preconception care is to improve the health of each woman prior to conception by identifying risk factors for adverse maternal or fetal outcome, providing education and counseling targeted to the patient′s individual needs, and treating or stabilizing medical conditions to optimize maternal and fetal outcomes.

Mode of delivery
Elective cesarean section (CS) at 38 weeks of pregnancy before the onset of labor or rupture of membrane decreases transmission by 50-80%. [36],[37] This transmission rate is further reduced to 2% when elective CS is combined with AZT prophylaxis. However, in mothers who have viral load < 1000 c/ml or have CS done after the onset of labor or rupture of membranes, there is no evidence of any benefit of CS in preventing perinatal transmission in fact, the risk of infectious complications increases 5-7 fold. So the decision of elective CS is based on the risk/benefit ratio.

Breastfeeding
The breast milk of HIV-infected mothers contains proviral HIV and free virus, as well as protective factors such as HIV antibodies and a glycoprotein that inhibits HIV binding to CD4+ cells. [38],[39] Despite the presence of these protective factors, a number of cases have been documented of transmission of HIV by breastfeeding. [40] The risk appears to be more during the first 4-6 months. [41] The risk of transmission is related to the duration of breast feeding, amount of virus in the breast milk, presence of HIV antibodies in the milk and whether or not breastfeeding is exclusive or mixed with other supplementary feeds. Mastitis, breast abscess, cracked nipples; infants with thrush, prolonged breastfeeding, and primary infection during pregnancy are other risk factors. In developed countries, breastfeeding is discouraged, however, in developing countries where formula puts the infant at high risk for other infections, breastfeeding is critical for infant nutrition and survival. [9]

Safety and adverse effects of antiretrovirals in pregnancy
Short-term safety and tolerance of antiretroviral prophylactic regimens has been demonstrated in all controlled clinical trials but data on long-term safety and on patterns of resistance is still being compiled. The following antiretrovirals should be avoided during pregnancy: Efavirenz (EFV), hydroxyurea, didanosine + stavudine (ddI + d4T), liquid amprenavir. [42] EFV causes neural tube defects in the first trimester while ddI + d4T causes severe lactic acidosis and/or hepatotoxicity. Nevirapine (NVP) causes fatal hepatic necrosis when given to pregnant women with CD4+ cells counts > 250/mm 3 , although it appears safe at delivery with only a concern for resistance with a single dose. Early pregnancy-associated nausea and vomiting may cause difficulty in antiretroviral administration or may exacerbate gastrointestinal side effects. Hyperglycemia and diabetes mellitus have been reported among patients taking protease inhibitors. [43]

Resistance
The frequency of NVP resistance is 60-70% with a single dose [44] with higher rates of NNRTI resistance mutations, especially K103N. In one trial, 15-24% of the mothers had NVP resistance six weeks postpartum with a single dose, which was no longer detected at 12 months. [45] But the probability that they were archived is supported by a lower rate of response to subsequent treatment with NVP-based HAART. [46] With AZT, development of resistance requires 4-6 months and AZT-resistant strains are infrequently transmitted. [47]

Conclusion

With the increase in pediatric HIV infection, there is a substantial impact on childhood mortality. MTCT not only increases the load of HIV-positive children on society, but also causes social problems by increasing the number of single parent-children or orphans after the death of one or both parents due to AIDS. Therefore, all pregnant women with HIV infection should be handled with utmost care, as there is a great potential of preventing HIV through vertical transmission. Antiretroviral prophylaxis either by combination therapy or a single agent, is recommended for all pregnant women with HIV-1 infection with careful and regular monitoring of the pregnancy and potential toxicities. In order to provide universal access to these services, further scale-up is planned up to the level of Community Health Centre and the Primary Health Centre, as well as in the private sector by forming public-private partnerships. Through these measures, NACO hopes to achieve the target of reducing the proportion of infants infected with HIV/AIDS by 50% by 2010. Still, the challenge for the future is to find the most cost-effective and feasible intervention to achieve 0% transmission of HIV from an infected mother to her child.

References

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