National audit of perinatal HIV infections in the UK, 2006-2013: what lessons can be learnt?

OBJECTIVES: The aim of the study was to investigate circumstances surrounding perinatal transmissions of HIV (PHIVs) in the UK. METHODS: The National Study of HIV in Pregnancy and Childhood conducts comprehensive surveillance of all pregnancies in women diagnosed with HIV infection and their infants in the UK; reports of all HIV-diagnosed children are also sought, regardless of country of birth. Children with PHIV born in 2006-2013 and reported by 2014 were included in an audit, with additional data collection via telephone interviews with clinicians involved in each case. Contributing factors for each transmission were identified, and cases described according to main likely contributing factor, by maternal diagnosis timing. RESULTS: A total of 108 PHIVs were identified. Of the 41 (38%) infants whose mothers were diagnosed before delivery, it is probable that most were infected in utero, around 20% intrapartum and 20% through breastfeeding. Timing of transmission was unknown for most children of undiagnosed mothers. For infants born to diagnosed women, the most common contributing factors for transmission were difficulties with engagement and/or antiretroviral therapy (ART) adherence in pregnancy (14 of 41) and late antenatal booking (nine of 41); for the 67 children with undiagnosed mothers, these were decline of HIV testing (28 of 67) and seroconversion (23 of 67). Adverse social circumstances around the time of pregnancy were reported for 53% of women, including uncertain immigration status, housing problems and intimate partner violence. Eight children died, all born to undiagnosed mothers. CONCLUSIONS: Priority areas requiring improvement include reducing incident infections, improving ART adherence and facilitating better engagement in care, with attention to addressing the health inequalities and adverse social situations faced by these women.

The incidence of congenital syphilis in the United Kingdom: February 2010 to January 2015.

OBJECTIVE: To estimate the incidence of congenital syphilis in the UK. DESIGN: Prospective study. SETTING AND POPULATION: United Kingdom. METHODS: Children born between February 2010 and January 2015 with a suspected diagnosis of congenital syphilis were reported through an active surveillance system. MAIN OUTCOME MEASURES: Number of congenital syphilis cases and incidence. RESULTS: For all years, reported incidence was below the WHO threshold for elimination (<0.5/1000 live births). Seventeen cases (12 male, five female) were identified. About 50% of infants (8/17) were born preterm (<37 weeks' gestation): median birthweight 2000 g (865-3170 g). Clinical presentation varied from asymptomatic to acute disease, including severe anaemia, hepatosplenomegaly, rhinitis, thrombocytopaenia, skeletal damage, and neurosyphilis. One infant was deaf and blind. Median maternal age was 20 years (17-31) at delivery. Where maternal stage of infection was recorded, 6/10 had primary, 3/10 secondary and 1/10 early latent syphilis. Most mothers were white (13/16). Country of birth was recorded for 12 mothers: UK (n = 6), Eastern Europe (n = 3), Middle East (n = 1), and South East Asia (n = 2). The social circumstances of mothers varied and included drug use and sex work. Some experienced difficulty accessing health care. CONCLUSION: The incidence of congenital syphilis is controlled and monitored by healthcare services and related surveillance systems, and is now below the WHO elimination threshold. However, reducing the public health impact of this preventable disease in the UK is highly dependent on the successful implementation of WHO elimination standards across Europe. TWEETABLE ABSTRACT: Congenital syphilis incidence in the UK is at a very low level and well below the WHO elimination threshold.

Syphilis screening in pregnancy in the United Kingdom, 2010-2011: a national surveillance study.

OBJECTIVE: To evaluate the national antenatal syphilis screening programme and provide evidence for improving screening and management strategies. DESIGN: National population-based surveillance. SETTING: United Kingdom (UK). POPULATION: All pregnant women screening positive for syphilis, 2010-2011. METHODS: Demographic, laboratory and treatment details for each pregnancy were collected from UK antenatal units (~210), along with follow-up information on all infants born to women requiring syphilis treatment in pregnancy. MAIN OUTCOME MEASURES: Proportion of women with newly or previously diagnosed syphilis among those with positive screening tests in pregnancy; proportion requiring treatment. RESULTS: Overall, 77% (1425/1840) of reported pregnancies were confirmed syphilis screen-positive. Of these, 71% (1010/1425) were in women with previously diagnosed syphilis (155 requiring treatment), 26% (374/1425) with newly diagnosed syphilis (all requiring treatment) and 3% (41/1425) required treatment but the reason for treatment was unclear. Thus 40% (570/1425) required treatment overall; of these, 96% (516/537) were treated (missing data: 33/570), although for 18% (83/456), this was not until the third trimester (missing data: 60/537). Follow up of infants born to treated women was poor, with at least a third not followed. Six infants were diagnosed with congenital syphilis; two mothers were untreated, three had delayed treatment and one had incomplete treatment (first trimester). CONCLUSION: Over 2 years, among pregnant women with confirmed positive syphilis screening results in the UK, a quarter had newly diagnosed infections and 40% required treatment. Despite high uptake of treatment, antenatal syphilis management could be improved by earlier detection, earlier treatment, and stronger links between healthcare teams. TWEETABLE ABSTRACT: 25% of pregnant women screening positive for syphilis in the UK were newly diagnosed and 40% needed treatment.

Presentation for care and antenatal management of HIV in the UK, 2009-2014.

OBJECTIVES: Despite very low rates of vertical transmission of HIV in the UK overall, rates are higher among women starting antenatal antiretroviral therapy (ART) late. We investigated the timing of key elements of the care of HIV-positive pregnant women [antenatal care booking, HIV laboratory assessment (CD4 count and HIV viral load) and antenatal ART initiation], to assess whether clinical practice is changing in line with recommendations, and to investigate factors associated with delayed care. METHODS: We used the UK's National Study of HIV in Pregnancy and Childhood for 2009-2014. Data were analysed by fitting logistic regression and Cox proportional hazards models. RESULTS: A total of 5693 births were reported; 79.5% were in women diagnosed with HIV prior to that pregnancy. Median gestation at antenatal booking was 12.1 weeks [interquartile range (IQR) 10.0-15.6 weeks] and booking was significantly earlier during 2012-2014 vs. 2009-2011 (P < 0.001), although only in previously diagnosed women. Overall, 42.2% of pregnancies were booked late (≥ 13 gestational weeks). Among women not already on treatment, antenatal ART commenced at a median of 21.4 (IQR18.1-24.5) weeks and started significantly earlier in the most recent time period (P < 0.001). Compared with previously diagnosed women, those newly diagnosed during the current pregnancy booked later for antenatal care and started antenatal ART later (both P < 0.001). Multivariable analyses revealed demographic variations in access to or uptake of care, with groups including migrants and parous women initiating care later. CONCLUSIONS: Although women are accessing antenatal and HIV care earlier in pregnancy, some continue to face barriers to timely initiation of antenatal care and ART.

Duration of ruptured membranes and mother-to-child HIV transmission: a prospective population-based surveillance study.

OBJECTIVE: To investigate the association between duration of rupture of membranes (ROM) and mother-to-child HIV transmission (MTCT) rates in the era of combination antiretroviral therapy (cART). DESIGN: The National Study of HIV in Pregnancy and Childhood (NSHPC) undertakes comprehensive population-based surveillance of HIV in pregnant women and children. SETTING: UK and Ireland. POPULATION: A cohort of 2398 singleton pregnancies delivered vaginally, or by emergency caesarean section, in women on cART in pregnancy during the period 2007-2012 with information on duration of ROM; HIV infection status was available for 1898 infants. METHODS: Descriptive analysis of NSHPC data. MAIN OUTCOME MEASURES: Rates of MTCT. RESULTS: In 2116 pregnancies delivered at term, the median duration of ROM was 3 hours 30 minutes (interquartile range, IQR 1-8 hours). The overall MTCT rate for women delivering at term with duration of ROM ≥4 hours was 0.64% compared with 0.34% for ROM <4 hours, with no significant difference between the groups (OR 1.90, 95% CI 0.45-7.97). In women delivering at term with a viral load of <50 copies/ml, there was no evidence of a difference in MTCT rates with duration of ROM ≥4 hours, compared with <4 hours (0.14% for ≥4 hours versus 0.12% for <4 hour; OR 1.14, 95% CI 0.07-18.27). Among infants born preterm with infection status available, there were no transmissions in 163 deliveries where the maternal viral load was <50 copies/ml. CONCLUSIONS: No association was found between duration of ROM and MTCT in women taking cART. TWEETABLE ABSTRACT: Rupture of membranes of more than 4 hours is not associated with MTCT of HIV in women on effective ART delivering at term.

British HIV Association and Children's HIV Association position statement on infant feeding in the UK 2011.

To prevent the transmission of HIV infection during the postpartum period, the British HIV Association and Children's HIV Association (BHIVA/CHIVA) continue to recommend the complete avoidance of breast feeding for infants born to HIV-infected mothers, regardless of maternal disease status, viral load or treatment.

Antiretroviral therapy and preterm delivery-a pooled analysis of data from the United States and Europe.

OBJECTIVE: To investigate reported differences in the association between highly active antiretroviral therapy (HAART) in pregnancy and the risk of preterm delivery among HIV-infected women. DESIGN: Combined analysis of data from three observational studies. SETTING: USA and Europe. POPULATION: A total of 19, 585 singleton infants born to HIV-infected women, 1990-2006. METHODS: Data from the Pediatric Spectrum of HIV Disease project (PSD), a US monitoring study, the European Collaborative Study (ECS), a consented cohort study, and the National Study of HIV in Pregnancy and Childhood (NSHPC), the United Kingdom and Ireland surveillance study. MAIN OUTCOME MEASURE: Preterm delivery rate (<37 weeks of gestation). RESULTS: Compared with monotherapy, HAART was associated with increased preterm delivery risk in the ECS (adjusted odds ratio [AOR] 2.40, 95% CI 1.49-3.86) and NSHPC (AOR 1.43, 95% CI 1.10-1.86), but not in the PSD (AOR 0.92, 95% CI 0.67-1.26), after adjusting for relevant covariates. Because of heterogeneity, data were not pooled for this comparison, but heterogeneity disappeared when HAART was compared with dual therapy (P = 0.26). In a pooled analysis, HAART was associated with 1.5-fold increased odds of preterm delivery compared with dual therapy (95% CI 1.19-1.87, P=0.001), after adjusting for covariates. CONCLUSIONS: Heterogeneity in the association between HAART and preterm delivery was not explained by study design, adjustment for confounders or a standard analytical approach, but may have been the result of substantial differences in populations and data collected. The pooled analysis comparing HAART with dual therapy showed an increased risk of preterm delivery associated with HAART.

Rubella seroprevalence in pregnant women in North Thames: estimates based on newborn screening samples.

OBJECTIVES: Routine screening for rubella susceptibility is recommended in the UK so that women found to be susceptible can be offered immunization in the post partum period. We demonstrate the use of newborn dried blood spot samples linked to routine vital statistics datasets to monitor rubella susceptibility in pregnant women and to investigate maternal characteristics as determinants of rubella seronegativity. SETTING: North Thames region of England (including large parts of inner London). METHODS: Maternally acquired rubella IgG antibody levels were measured in 18882 newborn screening blood spot samples. Latent class regression finite mixture models were used to classify samples as seronegative to rubella. Data on maternal country of birth were available through linkage to birth registration data. RESULTS: An estimated 2.7% (95% CI 2.4%-3.0%) of newly delivered women in North Thames were found to be seronegative. Mothers born abroad, particularly in Sub-Saharan Africa and South Asia, were more likely to be seronegative than UK-born mothers, with adjusted odds ratios of 4.2 (95% CI 3.1-5.6) and 5.0 (3.8-6.5), respectively. Mothers under 20 years were more likely to be seronegative than those aged 30 to 34. CONCLUSION: Our findings highlight the need for vaccination to be targeted specifically at migrant women and their families to ensure that they are protected from rubella in pregnancy and its serious consequences.

Vertically acquired HIV diagnosed in adolescence and early adulthood in the United Kingdom and Ireland: findings from national surveillance.

OBJECTIVE: The aim of the study was to describe the characteristics of young people with vertically acquired HIV diagnosed aged > or =13 years. METHODS: A retrospective review of HIV diagnoses reported to well-established national paediatric and adult HIV surveillance systems in the United Kingdom/Ireland was conducted. RESULTS: Forty-two young people with vertically acquired HIV diagnosed aged > or =13 years were identified; 23 (55%) were female, 40 (95%) were black African and 36 (86%) were born in sub-Saharan Africa. The median age at HIV diagnosis was 14 years (range, 13-20 years). Half of the patients presented with symptoms; the remainder were screened for HIV following diagnosis of a relative. The median CD4 count at diagnosis was 210 cells/microL (range, 0-689 cells/microL), 12 patients (29%) were diagnosed with AIDS at HIV diagnosis or subsequently, and 34 (81%) started combination antiretroviral therapy (ART), most (31 of 34) within a year of diagnosis. CONCLUSION: A small number of young people with vertically acquired HIV survive childhood without ART and are diagnosed at age > or =13 years in the United Kingdom/Ireland. Half of the patients were asymptomatic, highlighting the importance of considering HIV testing for all offspring of HIV-infected women, regardless of age or symptoms. Increased awareness among clinicians and parents is required to reduce delayed presentation with advanced disease and to avoid onward transmission as these young people become sexually active.

Trends in management and outcome of pregnancies in HIV-infected women in the UK and Ireland, 1990-2006.

OBJECTIVE: To describe the changing demographic profile of diagnosed HIV-infected pregnant women over time and trends in pregnancy outcome, uptake of interventions and mother-to-child transmission. DESIGN: National surveillance study. SETTING: UK and Ireland. POPULATION: Diagnosed HIV-infected pregnant women, 1990-2006. METHODS: Active surveillance of obstetric and paediatric HIV conducted through the National Study of HIV in Pregnancy and Childhood. MAIN OUTCOME MEASURES: Maternal characteristics, pregnancy outcome, use of antiretroviral therapy, mode of delivery and mother-to-child transmission. RESULTS: A total of 8327 pregnancies were reported, increasing from 82 in 1990 to 1394 in 2006, with an increasing proportion from areas outside London. Injecting drug use as the reported risk factor for maternal HIV acquisition declined from 49.2% (185/376) in 1990-1993 to 3.1% (125/4009) in 2004-2006 (P < 0.001), while the proportion of women born in sub-Saharan Africa increased from 43.5% (93/214) in 1990-1993 to 78.6% (3076/3912) in 2004-2006 (P < 0.004). Reported pregnancy terminations decreased from 29.6% (111/376) in 1990-1993 to 3.4% (135/4009) in 2004-2006 (P < 0.001). Most (56.4%, 3717/6593) deliveries were by elective caesarean section, with rates highest in 1999 (66.4%, 144/217). Vaginal deliveries increased from 16.6% (36/217) in 1999 to 28.3% (321/1136) in 2006 (P < 0.001). Use of antiretroviral therapy in pregnancy increased over time, reaching 98.4% (1092/1110) in 2006, and the overall mother-to-child transmission rate declined from 18.5% (35/189) in 1990-1993 to 1.0% (29/2832) in 2004-2006. CONCLUSIONS: The annual number of reported pregnancies increased dramatically between 1990 and 2006, with changing demographic and geographic profiles and substantial changes in pregnancy management and outcome.

Analysis of rubella antibody distribution from newborn dried blood spots using finite mixture models.

Eluted dried blood spot specimens from newborn screening, collected in 2004 in North Thames and anonymously linked to birth registration data, were tested for maternally acquired rubella IgG antibody as a proxy for maternal antibody concentration using an enzyme-linked immunosorbent assay. Finite mixture regression models were fitted to the antibody concentrations from 1964 specimens. The Bayesian Information Criterion (BIC) was used as a model selection criterion to avoid over-fitting the number of mixture model components. This allowed investigation of the independent effect of maternal age and maternal country of birth on rubella antibody concentration without dichotomizing the outcome variable using cut-off values set a priori. Mixture models are a highly useful method of analysis in seroprevalence studies of vaccine-preventable infections in which preset cut-off values may overestimate the size of the seronegative population.

Agreement of rubella IgG antibody measured in serum and dried blood spots using two commercial enzyme-linked immunosorbent assays.

Cases of congenital rubella are now rare in the United Kingdom. However, in certain areas such as London, where a significant proportion of pregnant women has been born abroad and uptake of trivalent measles-mumps-rubella (MMR) vaccination is low, the risk of a rubella outbreak remains. Prior to carrying out a seroprevalence study using rubella IgG antibody in newborn dried blood spots as an indirect marker of maternal immunity, rubella IgG antibody concentrations in serum and dried blood spot samples were investigated. Anonymous paired serum-dried blood spot samples left over from occupational health screening were tested for rubella IgG antibody by two commercially available enzyme-linked immunosorbent assays (ELISAs) (Dade Behring, Marburg, Germany, and Diesse, Siena, Italy). Agreement between serum samples and dried blood spot samples was high for both assays. There were no significant differences in antibody concentrations in paired samples, as 67 of 73 samples tested with the Diesse ELISA (91.8%), and 76 out of 79 samples tested with the Dade Behring ELISA (96.2%) were within two standard deviations of the mean difference. Commercial ELISAs are an appropriate test for seroprevalence surveys based on rubella IgG in dried blood spot samples.

HIV-1 subtypes in pregnant women in the UK.

We analyse the distribution of HIV-1 subtypes in HIV-1-seropositive samples from 333,270 residual neonatal dried blood spot samples tested for routine newborn screening tests in the UK between July 1999 and December 2002. Of the 813 antibody-positive samples shown to contain passively acquired, maternal HIV-1 for which subtyping was attempted, 333 (41%) could not be subtyped due to cross-reactivity or low values of the assay results, and 480 (59%) were classified as B (35, 7.3%) or non-B (445, 92.7%). The proportions of subtyped B samples differed significantly (P=0.004) between those from neonates whose mothers were born in the UK (21.4%) and those from neonates whose mothers were known to be born abroad (7%). Using a serological approach to establish viral serotype, we document the distribution of HIV-1 subtypes in infected pregnant women in the UK.

Monitoring the effectiveness of HIV and STI prevention initiatives in England, Wales, and Northern Ireland: where are we now?

Primary and secondary prevention are essential components of the response to HIV and sexually transmitted infections (STIs). We present findings from nationally implemented HIV/STI prevention interventions. In 2003, of those attending STI clinics at least 64% of men who have sex with men (MSM) and 55% of heterosexuals accepted a confidential HIV test; 88% of all HIV infections in women giving birth in England were diagnosed before delivery; 85% of MSM eligible for hepatitis B vaccination received a first dose of vaccine at their first STI clinic attendance; 74% of STI clinic attendees for emergency appointments, and 20% of those for routine appointments were seen within 48 hours of initiating an appointment; the National Chlamydia Screening Programme in England found a positivity of 10% and 13% among young asymptomatic women and men, respectively. Prevention initiatives have seen recent successes in limiting further HIV/STI transmission. However, more work is required if current levels of transmission are to be reduced.

Recent trends in HIV and other STIs in the United Kingdom: data to the end of 2002.

Sexual health in the United Kingdom has deteriorated in recent years with further increases in HIV and other sexually transmitted infections (STIs) reported in 2002. This paper describes results from the available surveillance data in the United Kingdom from the Health Protection Agency and its national collaborators. The data sources range from voluntary reports of HIV/AIDS from clinicians, CD4 cell count monitoring, a national census of individuals living with HIV, and the Unlinked Anonymous Programme, to statutory reports of STIs from genitourinary medicine (GUM) clinics and enhanced STI surveillance systems. In 2002, an estimated 49500 adults aged over 15 years were living with HIV in the United Kingdom, of whom 31% were unaware of their infection. Diagnoses of new HIV infections have doubled from 1997 to 2002, mainly driven by heterosexuals who acquired their infection abroad. HIV transmission also continues within the United Kingdom, particularly among homo/bisexual men who, in 2002, accounted for 80% of all newly diagnosed HIV infections acquired in the United Kingdom. New diagnoses of syphilis have increased eightfold, and diagnoses of chlamydia and gonorrhoea have doubled from 1997 to 2002 overall; STI rates disproportionately affect homo/bisexual men and young people. Effective surveillance is essential in the provision of timely information on the changing epidemiology of HIV and other STIs; this information is necessary for the targeting of prevention efforts and through providing baseline information against which progress towards targets can be monitored.

Decline in mortality, AIDS, and hospital admissions in perinatally HIV-1 infected children in the United Kingdom and Ireland.

OBJECTIVE: To describe changes in demographic factors, disease progression, hospital admissions, and use of antiretroviral therapy in children with HIV. DESIGN: Active surveillance through the national study of HIV in pregnancy and childhood (NSHPC) and additional data from a subset of children in the collaborative HIV paediatric study (CHIPS). SETTING: United Kingdom and Ireland. PARTICIPANTS: 944 children with perinatally acquired HIV-1 under clinical care. MAIN OUTCOME MEASURES: Changes over time in progression to AIDS and death, hospital admission rates, and use of antiretroviral therapy. RESULTS: 944 children with perinatally acquired HIV were reported in the United Kingdom and Ireland by October 2002; 628 (67%) were black African, 205 (22%) were aged > or = 10 years at last follow up, 193 (20%) are known to have died. The proportion of children presenting who were born abroad increased from 20% in 1994-5 to 60% during 2000-2. Mortality was stable before 1997 at 9.3 per 100 child years at risk but fell to 2.0 in 2001-2 (trend P < 0.001). Progression to AIDS also declined (P < 0.001). From 1997 onwards the proportion of children on three or four drug antiretroviral therapy increased. Hospital admission rates declined by 80%, but with more children in follow up the absolute number of admissions fell by only 26%. CONCLUSION: In children with HIV infection, mortality, AIDS, and hospital admission rates have declined substantially since the introduction of three or four drug antiretroviral therapy in 1997. As infected children in the United Kingdom and Ireland are living longer, there is an increasing need to address their medical, social, and psychological needs as they enter adolescence and adult life.

Pneumocystis carinii pneumonia and cytomegalovirus infection in children with vertically acquired HIV infection.

OBJECTIVES: The outcome of Pneumocystis carinii pneumonia (PCP) in HIV-infected infants is poor, and the role of cytomegalovirus (CMV) co-infection in the course and outcome of PCP is unclear. This study describes the prevalence, clinical characteristics, management and changes in survival over time of vertically HIV-infected infants developing PCP and/or CMV infection. METHODS: Data on children with HIV, born in the UK and Ireland and reported to the National Study of HIV in Pregnancy and Childhood, with PCP and/or CMV were combined with clinical information collected from reporting paediatricians. RESULTS: By April 1998, 340 vertically HIV-infected children had been reported, of whom 93 had PCP and/or CMV, as their first AIDS indicator disease; 85 (91%) were infants. Among infants with PCP, 79% were born to mothers not diagnosed as HIV infected, and there was an independent and statistically significant association with breast-feeding, being black African, and developing CMV disease. Median survival after PCP and/or CMV was significantly better in those born between 1993 and 1998 compared with those born before 1993 (P = 0.009), and worse than after other AIDS diagnoses (P = 0.01). Infants with dual infection were more likely to be ventilated (P = 0.003) and receive corticosteroids (P = 0.002) than those with PCP alone. CONCLUSION: Although survival from PCP and CMV has improved over time, these remain serious and potentially fatal infections among infants in whom maternal HIV status is not recognized in pregnancy. Breast-feeding increases the risk of combined PCP and CMV infection, which is associated with severe disease.

Active surveillance of hepatitis C infection in the UK and Ireland.

AIM: To investigate the prevalence, distribution, and clinical details of paediatric hepatitis C virus (HCV) infection in the UK and Ireland. METHODS: Active monthly surveillance questionnaire study coordinated through the British Paediatric Surveillance Unit, to all consultant paediatricians in 1997 and 1998. RESULTS: A total of 182 HCV infected children were reported from 54 centres and by paediatricians from eight different specialties. In 40 children HCV was acquired through mother to child transmission (MTC children); 142 were infected by contaminated blood products (n = 134), organ transplantation (n = 2), needles (n = 4), or unknown risk factor (n = 2). Intravenous drug use was the risk factor for 35 mothers of MTC children. Twelve children were coinfected with HIV and four with HBV. Recent serum aspartate aminotransferase or alanine aminotransferase values were at least twofold greater than the upper limit of normal in 24 of 152 children; this occurred in five of 11 HIV coinfected children. Liver histology, available in 53 children, showed normal (7%), mild (74%), moderate (17%), or severe (2%) hepatitis. Twenty eight children had received therapy with interferon alfa. CONCLUSION: Most current paediatric HCV infection in UK and Ireland has been acquired from contaminated blood products, and most children are asymptomatic. There is a need for multicentre trials to inform clinical practice and development of good practice guidelines in this area. Long term follow up of this cohort of HCV infected children is planned to help determine the natural history over the long term of HCV acquired during infancy and childhood.

Vertical transmission rates for HIV in the British Isles: estimates based on surveillance data.

OBJECTIVE: To estimate and interpret time trends in vertical transmission rates for HIV using data from national obstetric and paediatric surveillance registers. DESIGN: Prospective study of HIV infected women reported through obstetric surveillance. HIV infection status of the child and onset of AIDS were reported through paediatric surveillance. Rates of vertical transmission and progression to AIDS rate were estimated by methods that take account of incomplete follow up of children with indeterminate infection status and delay in AIDS reporting. SETTING: British Isles. SUBJECTS: Pregnant women infected with HIV whose infection was diagnosed before delivery, and their babies. MAIN OUTCOME MEASURES: Mother to child transmission of infection and progression to AIDS in children. RESULTS: By January 1999, 800 children born to diagnosed HIV infected women who had not breast fed had been reported. Vertical transmission rates rose to 19.6% (95% confidence interval 8. 0% to 32.5%) in 1993 before falling to 2.2% (0% to 7.8%) in 1998. Between 1995 and 1998 use of antiretroviral treatment increased significantly each year, reaching 97% of live births in 1998. The rate of elective caesarean section remained constant, at around 40%, up to 1997 but increased to 62% in 1998. Caesarean section and antiretroviral treatment together were estimated to reduce risk of transmission from 31.6% (13.6% to 52.2%) to 4.2% (0.8% to 8.5%). The proportion of infected children developing AIDS in the first 6 months fell from 17.7% (6.8% to 30.8%) before 1994 to 7.2% (0% to 15. 7%) after, coinciding with increased use of prophylaxis against Pneumocystis carinii pneumonia. CONCLUSIONS: In the British Isles both HIV related morbidity and vertical transmission are being reduced through increased use of interventions.