HIV-seronegative Mothers Research Articles

The birds and the bees: do Puerto Rican mothers and daughters talk about sex?

Effective communication skills that foster responsible sexual decisions are known to have the potential to reduce the risky adolescent sexual behavior. It is well understood that maternal communication is a key element in modifying the adolescent sexual behavior. The objective of this qualitative study was to explore if Puerto Rican mothers of adolescent girls have conversations about sexuality with their daughters and the content of such conversations. A total of 22 HIV-seropositive mothers and 22 HIV-seronegative mothers were enrolled. Six focus groups were conducted, sessions were transcribed ad-verbum and coded for specific topics. All qualitative analysis was incorporated into Atlas.ti. Participants in both groups had a similar average age (mean=41 years old); but, the HIV-seropositive mothers were more likely single, less educated and unemployed. Regarding having engaged in conversations about sexuality and the topics covered, however, there were no differences revealed among HIV-seropositive mothers and seronegative mothers. In both groups, mothers understood the importance of these conversations, but most said they were difficult and uncomfortable. These findings reinforce the importance of communication between mothers and daughters for the prevention of STIs, HIV/AIDS, and teenage pregnancy in minority populations.Interventions are needed for mother and daughter to improve communication skills, communication about sexuality, and addressing prevention.

Low vaccine coverage among children born to HIV infected women in Niamey, Niger

Background: The effect of mother’s HIV-status on child vaccination is an important public health issue in countries with high HIV prevalence. We conducted a study in a primary healthcare center located in Niamey, the capital of Niger, which offers free of charge services to HIV positive and/or underprivileged mothers, with the aim of assessing: 1) vaccination coverage for children 0–36 months old, born to HIV-infected mothers, and 2) the impact of maternal HIV status on child vaccination. Methods: Mothers of children less than 36 months old attending the center were interviewed, to collect information on vaccines administered to their child, and family’s socio-demographic characteristics. Results: Overall, 502 children were investigated. Children of HIV-seropositive mothers were less likely to receive follow up vaccinations for Diphtheria-Tetanus-Pertussis (DTP) than those of HIV-seronegative mothers, with a prevalence ratio (PR) of 2.03 (95%CI: 1.58–2.61). Children born to HIV-seropositive mothers were less likely to miss vaccination for MMR than those born to HIV negative mothers, with a RR of 0.46 (95%CI: 0.30–0.72). Conclusions: Vaccine coverage among children born to HIV infected mothers was rather low. It is important to favor access to vaccination programs in this population.

Factors related to attrition in a cohort study of HIV in Malawi

Longitudinal studies face power reduction due to loss to follow up (LTFU). Bias may also arise because of differences between those who stay in the study and those who are LTFU. We studied factors associated with LTFU in a cohort of HIV seronegative and sera-positive mothers in urban Malawi. To bridge the existing gaps by examining the factors associated with attrition. Longitudinal study. Queen Elizabeth Central Hospital (QECH) and the Kamuzu Central Hospital in Blantyre, Malawi. One thousand three hundred and fifty three women who attended the prenatal clinic, between October 1989 and October 1990 were recruited as part of a study to determine rates and risk factors of sero-prevalence and sera-conversion of HIV-1 among this cohort. In this cohort study, 1353 women were enrolled at delivery and 1188 (88%) returned for the first follow-up visit at three months post-partum. Of those who returned, 177 (15%) were subsequently lost during the remaining months of follow-up. The main predictors of LTFU were younger maternal age, lower educational level of the father, HIV infection of the mother, lower birth weight of the index child and mother not being married. Researchers planning studies in developing countries should consider the impact of lower education and poorer infant health on study retention in developing countries.

Rubella immunization in human immunodeficiency virus type 1-infected children: cause for concern in vaccination strategies.

HIV infection can have important although sometimes unexpected consequences, such as contributing to enlargement of the pool of rubella-susceptible children. At the Federal University of São Paulo, Brazil, we assessed response to rubella immunization at 15 months of age in 15 human immunodeficiency virus type 1 (HIV)-infected children, 20 seroreverted children (SR) and 18 healthy control children born to HIV-seronegative mothers (CON). Blood samples were collected before and 3 months after vaccination. All HIV-infected children had started highly active antiretroviral therapy during their first 6 months of life. Serum samples were tested with a rubella IgG enzyme-linked immunosorbent assay kit. HIV children in immunologic categories 2/3 had lower rubella antibody titers (geometric mean, 33 IU/mL) than those from CON (125 IU/mL) and SR group (236 IU/mL) (Tukey, P = 0.01). Antibody values after vaccination were positively associated with CD4 T cell numbers and negatively associated with HIV viral load assessed immediately before vaccination. The percentage of children with protective antibodies after vaccination (above 10.0 IU/mL) was also significantly different among groups (Fisher's exact test, P = 0.013): CON, 94%; SR, 100%; HIV category 1, 100%; HIV category 2/3, 62%. HIV-infected children with a preserved immune system at measles-mumps-rubella immunization can have a good response to rubella vaccine. In contrast, those in more advanced categories for HIV infection respond poorly.

Post-neonatal infant mortality in Malawi: the importance of maternal health.

In a cohort study of mothers and their infants, information was collected from women attending the antenatal services of two hospitals in a rural area of Malawi and 561 of their babies were enrolled in a follow-up study. There were 128 with a low birthweight (LBW, <2500 g), 138 with fetal anaemia (FA, cord haemoglobin <12.5 g/dl), 42 with both and 228 with a normal birthweight and no FA. Infants were seen monthly for 1 year. Risk factors for post-neonatal infant mortality (PNIM) were calculated using Cox regression analysis adjusting for LBW and FA. PNIM was 9.3%. Respiratory infections and diarrhoeal disease were the principal attributable causes of death. PNIM increased with LBW (RR 3.08, 95% CI 1.51-6.23) but not significantly so with FA (RR 1.60, 95% CI 0.78-3.27). An additional effect on PNIM was observed with maternal HIV (RR 3.44, 95% CI 1.63-7.26) and malaria at the first antenatal visit (RR 2.26, 95% CI 1.09-4.73). Illiteracy was not associated with mortality. Placental malaria in HIV-seronegative mothers was significantly associated with increased PNIM. Improving birthweight through effective antimalarial control in pregnancy will lead to a reduction in PNIM. Reduction of HIV prevalence and prevention of mother-to-child transmission of HIV must be a main target for government health policy.

Malaria and human immunodeficiency virus infection as risk factors for anemia in infants in Kisumu, western Kenya.

The role of maternal and pediatric infection with human immunodeficiency virus type 1 (HIV-1) and malaria as risk factors for anemia was determined in a birth cohort of infants born to mothers participating in a study of the interaction between placental malaria and HIV infection, in Kisumu, Kenya. Between June 1996 and April 2000, 661 infants born to 467 HIV-seropositive and 194 HIV-seronegative mothers were monitored monthly from birth. At each visit a questionnaire was completed and a blood sample was collected for the determination of hemoglobin levels and detection of malaria and HIV. Anemia was common and increased from 13.6% at one month to 75% at six months and remained high throughout the second half of infancy. Placental malaria, infant malaria, and HIV infection of the infant were all associated with infant anemia in a multivariate model, adjusting for other co-variates found to be associated with infant anemia. The HIV-infected infants with malaria parasitemia had lower mean hemoglobin levels compared with HIV-uninfected infants, or HIV-infected infants without malaria, suggesting that HIV-infected infants are particularly vulnerable to the adverse consequences of malaria at this age. Early detection and prompt treatment of infant malaria and treatment of anemia as part of the study protocol failed to prevent most of the infants from becoming anemic. Although not proven effective in this study, micronutrient supplementation should be prospectively assessed in HIV-infected infants as a means of preventing anemia.

Microbicides 2000 conference. Welcoming remarks. Expanding our prevention options: the role of the international community in providing an enabling environment for microbicides.

Microbicides 2000 conference. Welcoming remarks. Expanding our prevention options: the role of the international community in providing an enabling environment for microbicides.

Maternal HIV-1 and HIV-2 infection and child survival in The Gambia.

To compare the survival of children born to HIV-1 or HIV-2 seropositive mothers with that of children born to HIV-seronegative mothers and to evaluate risk factors for mortality. Physician-blinded prospective study. One hundred and one HIV-1-seropositive, 243 HIV-2-seropositive pregnant women, and 468 HIV-seronegative women (control group) matched by age, parity, and health centre, were followed up in a study of mother-to-child transmission of HIV. Mothers and children were seen at 2 and 6 months of age and subsequently followed at 3-monthly intervals up to 18 months of age. HIV infection in children was diagnosed by polymerase chain reaction at 2, 9 or 18 months and by antibody assays at 18 months. Fifteen per cent of children born to HIV-1-infected mothers died compared with 7% of children born to HIV-2-infected mothers [hazard ratio, 2.3; 95% confidence interval (CI), 1.1-4.7; P = 0.02], and 6% of HIV-seronegative mothers (hazard ratio, 2.6; 95% CI, 1.4-5.0; P = 0.003). Six of the 17 children known to be HIV-1 infected died compared with none among the eight HIV-2-infected children (P = 0.13). High proviral load in the babies, high antenatal maternal RNA plasma viral load, and maternal death increased child mortality significantly. More children born to HIV-1-infected mothers died in comparison with those born to HIV-2-infected mothers or to mothers from the control group. This effect was due to excess death in HIV-1-infected infants which was associated with a high viral load in the affected mother and child.

Maternal plasma viral RNA levels determine marked differences in mother-to-child transmission rates ofHIV-1 and HIV-2 in The Gambia

To determine the rates of, and risk factors for, mother-to-child transmission (MCT) of HIV-1 and HIV-2 infection in The Gambia. A blinded, prospective, community-based cohort study of 29.549 pregnant women attending the eight largest antenatal clinics in The Gambia. Women were tested for HIV-1 and HIV-2 infection. Infected subjects and a group of HIV-seronegative women were followed with their babies until 18 months after delivery. Maternal CD4 cell count percentages were measured before and 18 months after delivery, and the antenatal plasma viral load was determined. Babies were tested for HIV by the polymerase chain reaction and/or serology at 2, 9 and 18 months of age. The study enrolled 144 women positive for HIV-1 and 294 for HIV-2 plus 565 seronegative pregnant women: the mean antenatal percentage CD4 cell counts of 96 HIV-1-positive, 223 HIV-2-positive and 125 HIV-seronegative mothers were 31% [95% confidence interval (CI) 28-33], 41% (95% CI 39-42) and 47% (95% CI 45-49), respectively. The geometric mean antenatal plasma viral load of 94 HIV-1-infected women was 15,100 copies x 10(3) ml (95% CI 10,400-19,000) which was much higher than that of 60 randomly selected HIV-2-infected women, which was 410 copies x 10(3) ml (95% CI 150-910) (P < 0.001). The estimated transmission rate of HIV-1 was 24.4% (95% CI 14.6-33.9) and that of HIV-2 was 4.0% (95% CI 1.9-7.4). Five of 17 HIV-1-positive and three of eight HIV-2-positive babies were infected after 2 months of age. Birth in the rainy season [odds ratio (OR) 2.9; 95% CI 1.2-7.2], a low postnatal CD4 cell percentage (OR for a 10% fall 2.4; 95% CI 1.1-5.1) and a high maternal plasma viral load (OR for a 10-fold increase 2.9; 95% CI 1.1-7.8) were risk factors for transmission that applied equally to both viruses. Low maternal HIV-2 RNA levels, which on average are 37-fold less than in HIV-1 infection, relate to the low MCT rate of HIV-2.

Mortality after the first year of life among human immunodeficiency virus type 1-infected and uninfected children.

HIV-infected and uninfected children who survived their first year of life were prospectively followed in Malawi to assess levels of mortality and related risk factors during the second and third years of life. Children with known HIV status from an earlier perinatal intervention trial were enrolled. These children [HIV-infected (Group A); HIV-uninfected but born to HIV-seropositive mothers (Group B); and children born to HIV-seronegative mothers (Group C)] were followed every 3 months until age 36 months. Mortality data were collected at each visit. Immunologic data (CD4+ percent) were collected at or immediately after enrollment. Overall 702 children were enrolled and 83 children died during follow-up. The mortality rate per 1000 person years of observation was 339.3 among Group A children, 46.3 among Group B children and 35.7 among Group C children. Among HIV-infected children the cumulative proportion surviving to age 24 months was 70% and those surviving to age 36 months was 55%. By age 32 months none of the severely immunosuppressed (CD4% < 15%) children had survived. The mortality differentials between HIV-infected and uninfected children persisted after adjusting for several risk factors. The major causes of death among infected children (n = 52) were wasting and respiratory conditions. Although all HIV-infected children had received childhood immunizations, mortality was high. Management of these children should include aggressive antimicrobial treatment, and evaluation of prophylactic regimens should be considered.

Human serum β2-microglobulin levels: correlation with total serum IgG and placental IgG transfer in HIV-infected and non-HIV infected individuals

The acquisition of maternal immunoglobulin G (IgG) is fundamental to the immune defence of the neonate. The receptor responsible for IgG transfer across the human placenta has also been implicated in the maintenance of IgG levels in the circulation. β 2-microglobulin is part of the Fc receptor (FcR) that has recently been purified from the human placenta. In HIV infection, increasing serum levels of total IgG and β 2-microglobulin are observed as the disease progresses. Herein, we have investigated the correlation between β 2-microglobulin and total serum IgG levels in HIV-seropositive mothers and their term neonates (HIV group, n=37), as well as in HIV-seronegative mothers and their term neonates (control group, n=50). Serum maternal β 2-microglobulin was directly correlated with total serum IgG levels in HIV-infected mothers ( r=0.58; P=0.0002), but not in healthy HIV-seronegative mothers ( r=−0.20; P=0.16). Maternal serum β 2-microglobulin was also inversely correlated with placental antibody transfer of total IgG in mother-newborn pairs from the HIV group ( r=0.38; P=0.02), but not from the control group ( r=0.15, P=0.31). These results seem to indicate that, in HIV infection, elevated serum β 2-microglobulin levels could be involved in maintenance of abnormally high total serum IgG concentrations; by interfering with the binding of IgG to Fc receptors at the maternal-fetal interface, they might also reduce IgG transfer. By contrast, in normal non-HIV infected individuals, serum β 2-microglobulin levels do not appear implicated in regulation of these two phenomena.

Increased transmission of vertical hepatitis C virus (HCV) infection to human immunodeficiency virus (HIV)-infected infants of HIV- and HCV-coinfected women.

The transmission of perinatal hepatitis C virus (HCV) infection was studied retrospectively in 62 infants born to 54 HCV- and human immunodeficiency virus (HIV)-coinfected women enrolled in a prospective natural history study of HIV transmission. Infant HCV infection was assessed by nested RNA polymerase chain reaction. The overall rate of vertical HCV transmission was 16.4% (9/62). Most HCV-infected children did not develop antibodies to HCV. The rate of HCV infection was higher among HIV-infected infants (40%) than among HIV-uninfected infants (7.5%; odds ratio, 8.2; P = .009). This difference in transmission was not related to differences in maternal HCV load, as measured by branched DNA assay, or mode of delivery. Why HIV-infected infants of HCV- and HIV-coinfected women have significantly higher rates of perinatal HCV transmission remains to be elucidated. The rate of HCV transmission in HIV-uninfected infants of HCV- and HIV-coinfected women is similar to that reported for infants born to HIV-seronegative mothers.

Serum levels of Fas/Apo-1 and Bcl-2 in children with HIV-1 infection.

Apoptosis of CD4-positive T cells is considered to be involved in depletion of CD4-positive T cells in adult patients with HIV-1 infection. In this report we evaluated serum levels of soluble Fas/Apo-1 and circulating bcl-2 protein (an antiapoptotic molecule) in HIV-1-infected children, and 30 HIV-1 seronegative children. Significantly higher levels of Fas/Apo-1 were observed in 13 HIV-1-infected children than in non-infected control children (p < 0.001), whereas serum levels of bcl-2 were significantly decreased (p=0.002). Seronegative children born to HIV-infected mothers displayed significantly decreased (p < 0.05) serum levels of bcl-2. By contrast, children born to HIV-seronegative mothers and suffering from acute lower respiratory infection had normal levels of bcl-2 and Fas/Apo-1. These data suggest that upregulation of Fas/Apo-1 along with downregulation of bcl-2 protein may contribute to apoptosis in children with HIV-1 infection.

Late postnatal transmission of human immunodeficiency virus type 1 infection from mothers to infants in Dar es Salaam, Tanzania.

To study late postnatal transmission of human immunodeficiency virus type 1 in a cohort of children born to HIV-1-seropositive mothers who delivered at Muhimbili Medical Centre in Dar es Salaam, Tanzania. Since 1991 a prospective cohort study of mother-to-child transmission of HIV-1 has been conducted at Muhimbili Medical Centre in Dar es Salaam. HIV-1-seropositive mothers and age-matched seronegative controls were recruited into the cohort at delivery together with their newborns. Diagnosis of HIV-1 infection in children was based on polymerase chain reaction, HIV-1 p24 antigen tests and HIV antibody tests. Late postnatal transmission was defined as HIV-1 infection occurring after 6 months of age in a child who was uninfected at 6 months of age and who had an HIV-1-seropositive mother. Children born to HIV-seronegative mothers were used as controls. Breast-feeding was universal in this cohort. CD4 and CD8 T lymphocytes were assayed by flow cytometry in the mothers. Among 139 children born to HIV-1-seropositive mothers and known to be HIV-uninfected at 6 months of age, 8 children became HIV-1-infected at the end of their first year of life or later. No conversions were observed in children younger than 11 months. The 8 conversions were observed during a follow-up covering 1555 child months between 6 and 27 months of age corresponding to a conversion rate of 6.2 per 100 child years. Among 260 children with HIV-seronegative mothers no child became HIV-infected during the follow-up. The percentage of CD4 T lymphocytes was similar in mothers with early and late transmission but was significantly lower in transmitting than in nontransmitting mothers. Because no HIV-1 infection occurred in children with HIV-seronegative mothers, we conclude that the observed infections at the end of the first year of life or later among children born to HIV-seropositive women were caused by late transmission from mother to child, most likely through breast-feeding.

Management of partial-thickness burn wounds by amniotic membrane: a cost-effective treatment in developing countries

Burns incidence in our country has been on the increase over the past two decades. Cost-effective management of burn wounds has become the prerogative as our annual budget for burn care is limited. We have used human amniotic membrane procured from HbSAg, HIV-seronegative mothers undergoing caesarean section as a temporary biological dressing on superficial and deep partial-thickness burns. The advantages of amniotic membrane cover are reduction in pain, early drying of the wound and epithelialization. This type of wound management has been used in 350 cases. It has reduced the number of days stay in hospital and the bulky dressings that are conventional. Considering the patient acceptability, reduced hospital stay and reduction in cost, we find that treatment of superficial and deep partial-thickness burns with amniotic membrane is ideal for a developing country.

Placental Transfer and Maternally Acquired Neonatal IgG Immunity in Human Immunodeficiency Virus Infection

Transplacental transfer of specific IgG antibodies was studied in 46 pairs of human immunodeficiency virus type 1 (HIV-1)-seropositive women and their neonates and in 53 pairs of healthy HIV-seronegative mothers and their newborns. Neonatal and maternal sera were assessed by nephelometry for total levels of serum IgG and by ELISA for IgG antibodies to herpes simplex virus (HSV), varicella-zoster virus (VZV), measles virus, tetanus toxoid, streptolysin O, and Streptococcus pneumoniae capsular antigens. Placental transfer of IgG antibodies to VZV, tetanus toxoid, measles, streptolysin O, and S. pneumoniae was decreased by maternal HIV infection. Maternal levels of total IgG had an independent effect on transfer of antibodies to HSV, VZV, measles, and S. pneumoniae. Neonatal antibody levels to tetanus toxoid, measles, and S. pneumoniae were significantly lower in the HIV group. Both maternal hypergammaglobulinemia and maternal HIV infection may contribute to these low antibody levels at birth and thus lead to early infection in this high-risk population.

Rates of mother-to-child transmission of HIV-1 in Africa, America, and Europe: results from 13 perinatal studies. The Working Group on Mother-To-Child Transmission of HIV.

The goal of this exercise was to provide estimates of the mother-to-child transmission rate (TR) of human immunodeficiency virus type 1 (HIV-1), calculated according to standardized methods. Prospective cohort studies in Africa (8), the Caribbean (1), Europe (3), and the U.S.A. (1) observed from birth children born to women known to be HIV infected at the time of delivery. TRs were calculated and compared by investigators during a meeting in Ghent (Belgium) in September 1993 according to agreed methodology. TRs were calculated following the direct and the indirect methods developed in 1992 by the Ghent Working Group. The direct method uses a classification of children born to HIV-seropositive mothers according to their probable HIV infection status at 15 months of age or before, if they die or are lost to follow-up. Minimum, intermediate, and maximum estimates of TR are computed depending on how children classified as indeterminate are counted. The indirect method is applied for studies with a comparison cohort of children born to HIV-seronegative mothers. TRs in developed countries ranged from 14 to 25% with the direct method (intermediate estimate). In the developing world, they ranged from 13 to 42% with the direct method, from 21 to 43% with the indirect method, and most of the studies reported a TR in the range of 25 to 30%. With use of a standardized methodology, the overall TR of HIV-1 tends to be higher in Africa than in Europe or the U.S.A.(ABSTRACT TRUNCATED AT 250 WORDS)

Childhood malaria parasitaemia and human immunodeficiency virus infection in Malawi

Malaria and human immunodeficiency virus (HIV) infection are major health problems in many areas in Sub-Saharan Africa. An interaction between malaria and HIV infection has been postulated, since both produce similar cellular immune responses, with a lowering of the CD4/CD8 lymphocyte ratio. The frequency of malaria parasitemia was examined in children born to HIV-seropositive and seronegative mothers attending regular postnatal visits. A prospective study on mother-to-infant transmission of HIV had been underway since 1989 in Queen Elizabeth Central Hospital, Blantyre, a major hospital in urban Malawi. Standard HIV serology was performed on pregnant women, after obtaining consent. To reduce the effect of selection bias and seasonality, HIV seropositive (case) and seronegative (control) mothers and their infants were enrolled at delivery. Children included in the study were 503 born to 494 HIV-seropositive mothers and 540 born to 536 HIV-seronegative mothers. At each 3-monthly postpartum visit a Giemsa-stained thick blood film from the child was examined for malaria parasites. Children born to HIV-seropositive mothers were tested for HIV antibodies at 12 and 18 months of age. Of the 353 children born to HIV-seropositive mothers, 82 children (23.2%) were found to be HIV seropositive by enzyme-linked immunosorbent assay and Western blotting at 12 and 18 months. No statistically significant difference was found in frequency of malaria parasitemia by maternal or infant HIV serostatus after controlling for child's age. There was, however, a significant trend of increase in high parasitemia with age, irrespective of the HIV serostatus of the mother or the child. The frequency of parasitemia was higher in the wet season than in the dry season. This study suggests that maternal or infant HIV infection does not alter susceptibility to, or the clinical course of, malaria in infants.

Neurodevelopmental Testing of Children Born to Human Immunodeficiency Virus Type 1 Seropositive and Seronegative Mothers: A Prospective Cohort Study in Kigali, Rwanda

The results of developmental testing of 218 children born to human immunodeficiency virus (HIV)-seropositive mothers and infected or uninfected themselves were compared with those of 218 children born to HIV-seronegative mothers in an ongoing cohort study in Kigali, Rwanda. When the children were 6, 12, 18, and 24 months of age, a specific neurodevelopmental examination was performed blindly by study physicians assessing gross motor development, fine motor development, language acquisition, and social contacts. Only one acute severe HIV-related encephalopathy was identified among the 50 infected children. The proportion of abnormal neurologic examinations in HIV-infected children varied from 15% to 40% according to age and was always higher than in HIV-uninfected children born to HIV-seropositive and seronegative mothers (< or = 5% or less of abnormal examinations at each time period). After excluding those children with clinical acquired immunodeficiency syndrome (AIDS) from the analysis, the proportion of abnormal examinations in infected children was 12.5% at 6 months, 16% at 12 months, 20% at 18 months, and 9% at 24 months of age and was still more frequent than in HIV-uninfected children. The developmental delay was principally due to significantly lower gross motor scores. HIV-1-infected children are more frequently developmentally delayed than uninfected children during the first 2 years of life in this African population. This developmental delay is related to the AIDS stage of pediatric HIV infection.

Estimating the rate of mother-to-child transmission of HIV. Report of a workshop on methodological issues Ghent (Belgium), 17–20 February 1992

In the last 8 years, numerous cohort studies have been conducted to estimate the rate of mother-to-child transmission (MTCT) of HIV. Many of these have faced problems in data collection and analysis, making it difficult to compare transmission rates between studies. This workshop on methodological aspects of the study of MTCT of HIV-1 was held in Ghent (Belgium) in February 1992. Fourteen teams of investigators participated, representing studies from Central (five) and Eastern Africa (three), Europe (two), Haiti (one) and the United States (three). A critical evaluation of the projects was carried out, under four headings: (1) enrollment and follow-up procedures, (2) diagnostic criteria and case definitions, (3) measurement and comparison of MTCT rates and (4) determinants of transmission. Reported transmission rates ranged from 13 to 32% in industrialized countries and from 25 to 48% in developing countries. However, no direct comparisons could be made because methods of calculation differed from study to study. Based on this review, a common methodology was developed. Agreement was reached on definitions of HIV-related signs/symptoms, paediatric AIDS and HIV-related deaths. A classification system of children born to HIV-1-infected mothers according to their probable HIV infection status during the first 15 months of life, allowed the elaboration of a direct method of computation of the transmission rate and of an indirect method for studies with a comparison group of children born to HIV-seronegative mothers. This standardized approach was subsequently applied to selected data sets. The methodology can now be applied to all studies with sufficient follow-up and comparisons made between transmission rates. This step is essential for assessing determinants of transmission and for the development of a common approach for the evaluation of interventions aimed at reducing or interrupting MTCT of HIV.