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Featured researches published by Clara Calvert.


Clinical Infectious Diseases | 2014

Vertical Transmission of Hepatitis C Virus: Systematic Review and Meta-analysis

Lenka Benova; Yousra A. Mohamoud; Clara Calvert; Laith J. Abu-Raddad

Updated pooled estimates of vertical hepatitis C (HCV) infection risk to children of HCV RNA–positive mothers ranges between 5.8% and 10.8%, depending on maternal HIV coinfection. Additional risk factors need to be captured and reported by future studies.


The Lancet | 2013

Effect of HIV infection on pregnancy-related mortality in sub-Saharan Africa: secondary analyses of pooled community-based data from the network for Analysing Longitudinal Population-based HIV/AIDS data on Africa (ALPHA)

Basia Zaba; Clara Calvert; Milly Marston; Raphael Isingo; Jessica Nakiyingi-Miiro; Tom Lutalo; Amelia C. Crampin; Laura Robertson; Kobus Herbst; Marie-Louise Newell; Jim Todd; Peter Byass; Ties Boerma; Carine Ronsmans

Summary Background Model-based estimates of the global proportions of maternal deaths that are in HIV-infected women range from 7% to 21%, and the effects of HIV on the risk of maternal death is highly uncertain. We used longitudinal data from the Analysing Longitudinal Population-based HIV/AIDS data on Africa (ALPHA) network to estimate the excess mortality associated with HIV during pregnancy and the post-partum period in sub-Saharan Africa. Methods The ALPHA network pooled data gathered between June, 1989 and April, 2012 in six community-based studies in eastern and southern Africa with HIV serological surveillance and verbal-autopsy reporting. Deaths occurring during pregnancy and up to 42 days post partum were defined as pregnancy related. Pregnant or post-partum person-years were calculated for HIV-infected and HIV-uninfected women, and HIV-infected to HIV-uninfected mortality rate ratios and HIV-attributable rates were compared between pregnant or post-partum women and women who were not pregnant or post partum. Findings 138 074 women aged 15–49 years contributed 636 213 person-years of observation. 49 568 women had 86 963 pregnancies. 6760 of these women died, 235 of them during pregnancy or the post-partum period. Mean prevalence of HIV infection across all person-years in the pooled data was 17·2% (95% CI 17·0–17·3), but 60 of 118 (50·8%) of the women of known HIV status who died during pregnancy or post partum were HIV infected. The mortality rate ratio of HIV-infected to HIV-uninfected women was 20·5 (18·9–22·4) in women who were not pregnant or post partum and 8·2 (5·7–11·8) in pregnant or post-partum women. Excess mortality attributable to HIV was 51·8 (47·8–53·8) per 1000 person-years in women who were not pregnant or post partum and 11·8 (8·4–15·3) per 1000 person-years in pregnant or post-partum women. Interpretation HIV-infected pregnant or post-partum women had around eight times higher mortality than did their HIV-uninfected counterparts. On the basis of this estimate, we predict that roughly 24% of deaths in pregnant or post-partum women are attributable to HIV in sub-Saharan Africa, suggesting that safe motherhood programmes should pay special attention to the needs of HIV-infected pregnant or post-partum women. Funding Wellcome Trust, Health Metrics Network (WHO).


Clinical Infectious Diseases | 2014

Vertical transmission of hepatitis C: Systematic review and meta-analysis

Lenka Benova; Yousra A. Mohamoud; Clara Calvert; Laith J. Abu-Raddad

Updated pooled estimates of vertical hepatitis C (HCV) infection risk to children of HCV RNA–positive mothers ranges between 5.8% and 10.8%, depending on maternal HIV coinfection. Additional risk factors need to be captured and reported by future studies.


AIDS | 2013

The contribution of HIV to pregnancy-related mortality: a systematic review and meta-analysis.

Clara Calvert; Carine Ronsmans

Objectives:Although much is known about the contribution of HIV to adult mortality, remarkably little is known about the mortality attributable to HIV during pregnancy. In this article we estimate the proportion of pregnancy-related deaths attributable to HIV based on empirical data from a systematic review of the strength of association between HIV and pregnancy-related mortality. Methods:Studies comparing mortality during pregnancy and the postpartum in HIV-infected and HIV-uninfected women were included. Summary estimates of the relative and attributable risks for the association between HIV and pregnancy-related mortality were calculated through meta-analyses. Varying estimates of HIV prevalence were used to predict the impact of the HIV epidemic on pregnancy-related mortality at the population level. Results:Twenty-three studies were included (17 from sub-Saharan Africa). Meta-analysis of the risk ratios indicated that HIV-infected women had eight times the risk of a pregnancy-related death compared with HIV-uninfected women [pooled risk ratio 7.74, 95% confidence interval (95% CI) 5.37–11.16]. The excess mortality attributable to HIV among HIV-infected pregnant and postpartum women was 994 per 100 000 pregnant women. We predict that 12% of all deaths during pregnancy and up to 1-year postpartum are attributable to HIV/AIDS in regions with a prevalence of HIV among pregnant women of 2%. This figure rises to 50% in regions with a prevalence of 15%. Conclusion:The substantial excess of pregnancy-related mortality associated with HIV highlights the importance of integrating HIV and reproductive health services in areas of high HIV prevalence and pregnancy-related mortality.


PLOS ONE | 2012

Identifying regional variation in the prevalence of postpartum haemorrhage: a systematic review and meta-analysis.

Clara Calvert; Sara L Thomas; Carine Ronsmans; Karen S. Wagner; Alma J Adler; Véronique Filippi

Objective To provide regional estimates of the prevalence of maternal haemorrhage and explore the effect of methodological differences between studies on any observed regional variation. Methods We conducted a systematic review of the prevalence of maternal haemorrhage, defined as blood loss greater than or equal to 1) 500 ml or 2) 1000 ml in the antepartum, intrapartum or postpartum period. We obtained regional estimates of the prevalence of maternal and severe maternal haemorrhage by conducting meta-analyses and used meta-regression to explore potential sources of between-study heterogeneity. Findings No studies reported the prevalence of antepartum haemorrhage (APH) according to our definitions. The prevalence of postpartum haemorrhage (PPH) (blood loss ≥500 ml) ranged from 7.2% in Oceania to 25.7% in Africa. The prevalence of severe PPH (blood loss ≥1000 ml) was highest in Africa at 5.1% and lowest in Asia at 1.9%. There was strong evidence of between-study heterogeneity in the prevalence of PPH and severe PPH in most regions. Meta-regression analyses suggested that region and method of measurement of blood loss influenced prevalence estimates for both PPH and severe PPH. The regional patterns changed after adjusting for the other predictors of PPH indicating that, compared with European women, Asian women have a lower prevalence of PPH. Conclusions We found evidence that Asian women have a very low prevalence of PPH compared with women in Europe. However, more reliable estimates will only be obtained with the standardisation of the measurement of PPH so that the data from different regions are comparable.


The Lancet | 2016

Quality maternity care for every woman, everywhere: a call to action

Marjorie Koblinsky; Cheryl A. Moyer; Clara Calvert; James Campbell; Oona M. R. Campbell; Andrea B Feigl; Wendy Graham; Laurel Hatt; Steve Hodgins; Zoe Matthews; Lori McDougall; Allisyn C. Moran; Allyala K Nandakumar; Ana Langer

To improve maternal health requires action to ensure quality maternal health care for all women and girls, and to guarantee access to care for those outside the system. In this paper, we highlight some of the most pressing issues in maternal health and ask: what steps can be taken in the next 5 years to catalyse action toward achieving the Sustainable Development Goal target of less than 70 maternal deaths per 100 000 livebirths by 2030, with no single country exceeding 140? What steps can be taken to ensure that high-quality maternal health care is prioritised for every woman and girl everywhere? We call on all stakeholders to work together in securing a healthy, prosperous future for all women. National and local governments must be supported by development partners, civil society, and the private sector in leading efforts to improve maternal-perinatal health. This effort means dedicating needed policies and resources, and sustaining implementation to address the many factors influencing maternal health-care provision and use. Five priority actions emerge for all partners: prioritise quality maternal health services that respond to the local specificities of need, and meet emerging challenges; promote equity through universal coverage of quality maternal health services, including for the most vulnerable women; increase the resilience and strength of health systems by optimising the health workforce, and improve facility capability; guarantee sustainable finances for maternal-perinatal health; and accelerate progress through evidence, advocacy, and accountability.


BMC Pregnancy and Childbirth | 2013

Estimating the prevalence of obstetric fistula: a systematic review and meta-analysis

Alma J Adler; Carine Ronsmans; Clara Calvert; Véronique Filippi

BackgroundObstetric fistula is a severe condition which has devastating consequences for a woman’s life. The estimation of the burden of fistula at the population level has been impaired by the rarity of diagnosis and the lack of rigorous studies. This study was conducted to determine the prevalence and incidence of fistula in low and middle income countries.MethodsSix databases were searched, involving two separate searches: one on fistula specifically and one on broader maternal and reproductive morbidities. Studies including estimates of incidence and prevalence of fistula at the population level were included. We conducted meta-analyses of prevalence of fistula among women of reproductive age and the incidence of fistula among recently pregnant women.ResultsNineteen studies were included in this review. The pooled prevalence in population-based studies was 0.29 (95% CI 0.00, 1.07) fistula per 1000 women of reproductive age in all regions. Separated by region we found 1.57 (95% CI 1.16, 2.06) in sub Saharan Africa and South Asia, 1.60 (95% CI 1.16, 2.10) per 1000 women of reproductive age in sub Saharan Africa and 1.20 (95% CI 0.10, 3.54) per 1000 in South Asia. The pooled incidence was 0.09 (95% CI 0.01, 0.25) per 1000 recently pregnant women.ConclusionsOur study is the most comprehensive study of the burden of fistula to date. Our findings suggest that the prevalence of fistula is lower than previously reported. The low burden of fistula should not detract from their public health importance, however, given the preventability of the condition, and the devastating consequences of fistula.


Tropical Medicine & International Health | 2013

Prevalence of placenta praevia by world region: a systematic review and meta-analysis

Jenny A. Cresswell; Carine Ronsmans; Clara Calvert; Véronique Filippi

(i) To estimate the prevalence burden of placenta praevia in each world region, and (ii) to investigate potential sources of heterogeneity.


Global Health Action | 2013

InterVA-4 as a public health tool for measuring HIV/AIDS mortality: a validation study from five African countries

Peter Byass; Clara Calvert; Jessica Miiro-Nakiyingi; Tom Lutalo; Denna Michael; Amelia C. Crampin; Simon Gregson; Albert Takaruza; Laura Robertson; Kobus Herbst; Jim Todd; Basia Zaba

Background Reliable population-based data on HIV infection and AIDS mortality in sub-Saharan Africa are scanty, even though that is the region where most of the world’s AIDS deaths occur. There is therefore a great need for reliable and valid public health tools for assessing AIDS mortality. Objective The aim of this article is to validate the InterVA-4 verbal autopsy (VA) interpretative model within African populations where HIV sero-status is recorded on a prospective basis, and examine the distribution of cause-specific mortality among HIV-positive and HIV-negative people. Design Data from six sites of the Alpha Network, including HIV sero-status and VA interviews, were pooled. VA data according to the 2012 WHO format were extracted, and processed using the InterVA-4 model into likely causes of death. The model was blinded to the sero-status data. Cases with known pre-mortem HIV infection status were used to determine the specificity with which InterVA-4 could attribute HIV/AIDS as a cause of death. Cause-specific mortality fractions by HIV infection status were calculated, and a person-time model was built to analyse adjusted cause-specific mortality rate ratios. Results The InterVA-4 model identified HIV/AIDS-related deaths with a specificity of 90.1% (95% CI 88.7–91.4%). Overall sensitivity could not be calculated, because HIV-positive people die from a range of causes. In a person-time model including 1,739 deaths in 1,161,688 HIV-negative person-years observed and 2,890 deaths in 75,110 HIV-positive person-years observed, the mortality ratio HIV-positive:negative was 29.0 (95% CI 27.1–31.0), after adjustment for age, sex, and study site. Cause-specific HIV-positive:negative mortality ratios for acute respiratory infections, HIV/AIDS-related deaths, meningitis, tuberculosis, and malnutrition were higher than the all-cause ratio; all causes had HIV-positive:negative mortality ratios significantly higher than unity. Conclusions These results were generally consistent with relatively small post-mortem and hospital-based diagnosis studies in the literature. The high specificity in cause of death attribution achieved in relation to HIV status, and large differences between specific causes by HIV status, show that InterVA-4 is an effective and valid tool for assessing HIV-related mortality.Background Reliable population-based data on HIV infection and AIDS mortality in sub-Saharan Africa are scanty, even though that is the region where most of the worlds AIDS deaths occur. There is therefore a great need for reliable and valid public health tools for assessing AIDS mortality. Objective The aim of this article is to validate the InterVA-4 verbal autopsy (VA) interpretative model within African populations where HIV sero-status is recorded on a prospective basis, and examine the distribution of cause-specific mortality among HIV-positive and HIV-negative people. Design Data from six sites of the Alpha Network, including HIV sero-status and VA interviews, were pooled. VA data according to the 2012 WHO format were extracted, and processed using the InterVA-4 model into likely causes of death. The model was blinded to the sero-status data. Cases with known pre-mortem HIV infection status were used to determine the specificity with which InterVA-4 could attribute HIV/AIDS as a cause of death. Cause-specific mortality fractions by HIV infection status were calculated, and a person-time model was built to analyse adjusted cause-specific mortality rate ratios. Results The InterVA-4 model identified HIV/AIDS-related deaths with a specificity of 90.1% (95% CI 88.7-91.4%). Overall sensitivity could not be calculated, because HIV-positive people die from a range of causes. In a person-time model including 1,739 deaths in 1,161,688 HIV-negative person-years observed and 2,890 deaths in 75,110 HIV-positive person-years observed, the mortality ratio HIV-positive:negative was 29.0 (95% CI 27.1-31.0), after adjustment for age, sex, and study site. Cause-specific HIV-positive:negative mortality ratios for acute respiratory infections, HIV/AIDS-related deaths, meningitis, tuberculosis, and malnutrition were higher than the all-cause ratio; all causes had HIV-positive:negative mortality ratios significantly higher than unity. Conclusions These results were generally consistent with relatively small post-mortem and hospital-based diagnosis studies in the literature. The high specificity in cause of death attribution achieved in relation to HIV status, and large differences between specific causes by HIV status, show that InterVA-4 is an effective and valid tool for assessing HIV-related mortality.


PLOS ONE | 2013

HIV and the Risk of Direct Obstetric Complications: A Systematic Review and Meta-Analysis

Clara Calvert; Carine Ronsmans

Background Women of reproductive age in parts of sub-Saharan Africa are faced both with high levels of HIV and the threat of dying from the direct complications of pregnancy. Clinicians practicing in such settings have reported a high incidence of direct obstetric complications among HIV-infected women, but the evidence supporting this is unclear. The aim of this systematic review is to establish whether HIV-infected women are at increased risk of direct obstetric complications. Methods and findings Studies comparing the frequency of obstetric haemorrhage, hypertensive disorders of pregnancy, dystocia and intrauterine infections in HIV-infected and uninfected women were identified. Summary estimates of the odds ratio (OR) for the association between HIV and each obstetric complication were calculated through meta-analyses. In total, 44 studies were included providing 66 data sets; 17 on haemorrhage, 19 on hypertensive disorders, five on dystocia and 25 on intrauterine infections. Meta-analysis of the OR from studies including vaginal deliveries indicated that HIV-infected women had over three times the risk of a puerperal sepsis compared with HIV-uninfected women [pooled OR: 3.43, 95% confidence interval (CI): 2.00–5.85]; this figure increased to nearly six amongst studies only including women who delivered by caesarean (pooled OR: 5.81, 95% CI: 2.42–13.97). For other obstetric complications the evidence was weak and inconsistent. Conclusions The higher risk of intrauterine infections in HIV-infected pregnant and postpartum women may require targeted strategies involving the prophylactic use of antibiotics during labour. However, as the huge excess of pregnancy-related mortality in HIV-infected women is unlikely to be due to a higher risk of direct obstetric complications, reducing this mortality will require non obstetric interventions involving access to ART in both pregnant and non-pregnant women.

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Jim Todd

University of London

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Tom Lutalo

Uganda Virus Research Institute

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