Jon Oyvind Odland
Datos Biográficos
| ID | 145369 |
|---|---|
| NOMBRE | Jon Oyvind Odland |
| NOMBRES | Jon Oyvind |
| APELLIDO | Odland |
| FIRMA | ODLAND J O |
| AFILIACIONES | Norwegian University of Science and Technology |
| ORCID | 0000-0002-2756-0732 |
| VERIFICADO | Sí |
| TOTAL DE OBRAS | 28 |
| TOTAL DE CITAS | 11 |
| TOTAL COMO AUTOR | 28 |
| TOTAL COMO EDITOR | 0 |
| PRIMER AÑO DE PUBLICACIÓN | 2004 |
| AÑO MÁS RECIENTE DE PUBLICACIÓN | 2024 |
| ÍNDICE H | 2 |
Concentrations of potentially toxic metals and trace elements in pregnant women and association with birth outcomes
Potentially toxic metals and trace elements have been used in Malawi for a long time. However, data on exposure to these elements by susceptible groups like pregnant women and its associations with reproductive health outcomes in Malawi and southern hemisphere is limited. We investigated the concentrations of potentially toxic metals as well as trace elements in pregnant women and assessed the relationship between the levels these elements in mat…
Awareness of postpartum depression among midwives and pregnant women in Arkhangelsk, Arctic Russia
BACKGROUND: Postpartum depression (PPD) affects approximately 17% of the women worldwide with nearly half of all cases going undetected. More research on maternal mental health, particularly among healthcare professionals and pregnant mothers, could help identify PPD risks and reduce its prevalence. OBJECTIVE: Given that awareness of PPD is a crucial preventive factor, we studied PPD awareness among midwives and pregnant women in Arkhangelsk, Arc…
Investigating the relationship between non-occupational pesticide exposure and metabolomic biomarkers
The relationship between pesticide exposures and metabolomics biomarkers is not well understood. We examined the changes in the serum metabolome (early biomarkers) and the metabolic pathways associated with various pesticide exposure scenarios (OPE: overall exposure, PEM: exposure in months, PEY: exposure in years, and PEU: reported specific pesticides use) using data from the Northern Finland Birth Cohort 1966 31-year cross-sectional examination…
Predictors of Maternal Serum Concentrations for Selected Persistent Organic Pollutants (POPs) in Pregnant Women and Associations with Birth Outcomes
Population exposure to persistent organic pollutants (POPs) may result in detrimental health effects, especially to pregnant women, developing foetuses and young children. We are reporting the findings of a cross-sectional study of 605 mothers in their late pregnancy, recruited between August 2020 and July 2021 in southern Malawi, and their offspring. The aim was to measure the concentrations of selected POPs in their maternal serum and indicate …
Emergency Craniotomy and Burr-Hole Trephination in a Low-Resource Setting
To evaluate the teaching effect of a trauma training program in emergency cranial neurosurgery in Cambodia on surgical outcomes for patients with traumatic brain injury (TBI). We analyzed the data of TBI patients who received emergency burr-hole trephination or craniotomy from a prospective, descriptive cohort study at the Military Region 5 Hospital between January 2015 and December 2016. TBI patients who underwent emergency cranial neurosurgery …
Experiences of Using Misoprostol in the Management of Incomplete Abortions
Complications after abortion are a major cause of maternal death. Incomplete abortions are common and require treatment with surgical or medical uterine evacuation. Even though misoprostol is a cheaper and safer option, it is rarely used in Malawi. To improve services, an intervention was performed to increase the use of misoprostol in post-abortion care. This study explored healthcare providers' perceptions and experiences with misoprostol in th…
Geographic and Ethnic Variations in Serum Concentrations of Legacy Persistent Organic Pollutants among Men in the Nenets Autonomous Okrug, Arctic Russia
The overwhelming majority of Arctic biomonitoring studies in humans include either pregnant or non-pregnant women of reproductive age while little attention is paid to toxic compounds concentrations in men. This study contributes with information of the present amounts of persistent organic pollutants (POPs) in men living in Arctic Russia. We studied the serum concentrations of 11 polychlorinated biphenyl (PCB) congeners and 17 organochlorine pes…
Maternal Blood Levels of Toxic and Essential Elements and Birth Outcomes in Argentina
Pregnant women's levels of toxic and essential minerals have been linked to birth outcomes yet have not been adequately investigated in South America. In Argentina, n = 696 maternal whole blood samples from Ushuaia ( n = 198) and Salta ( n = 498) were collected in 2011-2012 among singleton women at 36 ± 12 h postpartum and analyzed for blood concentrations of arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), copper (Cu), manganese (Mn), seleni…
Selenium Status, Its Interaction with Selected Essential and Toxic Elements, and a Possible Sex-Dependent Response In Utero, in a South African Birth Cohort
Selenium (Se) is an essential trace element and its deficiency in utero may affect fetus development and birth outcomes. The current study aimed to assess serum Se status at delivery and examine the possible association between Se levels and birth outcomes. The interaction of Se with selected essential and toxic elements as well as possible sex-dependent responses in utero were also evaluated. The negative association between Se levels and head c…
The Role of Leptin Levels in Adaptation to Cold Climates
Currently, adipose tissue is considered an endocrine organ that produces hormone-active substances, including leptin, which can play a key role in thermoregulation processes. Therefore, we performed a meta-analysis to investigate the influence of the climatic environment on leptin levels. A systematic literature search in the databases was carried out on 10 January 2020. Finally, 22 eligible articles were included in the current meta-analysis and…
In Utero Exposure to Aluminium and Other Neurotoxic Elements in Urban Coastal South African Women at Delivery
Aluminium (Al) is a non-essential neurotoxicant and there is limited information regarding exposure to Al in utero. This study sought to evaluate the in utero exposure to Al in urban South African women, its effects on birth outcomes and possible synergistic effects between Al, essential and neurotoxic elements such as lead (Pb), mercury (Hg) and arsenic (As), as well as a a potential sex-dependent response to these elements in neonates. This stu…
Serum Concentrations of Selected Organochlorines in Pregnant Women and Associations with Pregnancy Outcomes. A Cross-Sectional Study from Two Rural Settings in Cambodia
We conducted a cross-sectional study among 194 pregnant women from two low-income settings in Cambodia. The inclusion period lasted from October 2015 through December 2017. Maternal serum samples were analyzed for persistent organic pollutants (POPs). The aim was to study potential effects on birth outcomes. We found low levels of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCP), except for heptachlors, β-hexachlorocyclohexane…
An Increased Risk of Stunting among Newborns in Poorer Rural Settings
We conducted an observational study of 194 pregnant women from two different study sites in rural Cambodia. Socioeconomic and anthropometric data was obtained from the women and their newborns. In addition, we collected blood and urine samples from the women for further analyses in planned papers. There were significant differences between the two study groups for clinical outcomes. The mothers from the poorer area were shorter and weighed less a…
Incidence and Risk Factors of Pre-Eclampsia in the Paropakar Maternity and Women’s Hospital, Nepal
This study aims to determine the incidence of pre-eclampsia and distribution of risk factors of pre-eclampsia at Paropakar Maternity and Women's Hospital, Kathmandu, Nepal. A retrospective study included 4820 pregnant women from 17 September to 18 December 2017. Data were obtained from the medical records of the hospital's Statistics Department. Associations between the risk factors and pre-eclampsia were determined using logistic regression anal…
Health Risk Modifiers of Exposure to Persistent Pollutants among Indigenous Peoples of Chukotka
The aim of the study was to assess temporal trends in health risks related to most common persistent contaminants, including polychlorinated biphenyls (PCBs), dichloro-diphenyl-trichloroethanes (DDTs), lead (Pb), as well as mercury (Hg) among indigenous peoples living in coastal areas of Chukotka in Arctic Russia. This is examined in relation to exposure pathways and a range of social and behavioral factors capable of modifying the exposure to th…
Risk Factors for Ventricular Septal Defects in Murmansk County, Russia
Cardiovascular malformations are one of the most common birth defects among newborns and constitute a leading cause of perinatal and infant mortality. Although some risk factors are recognized, the causes of cardiovascular malformations (CVMs) remain largely unknown. In this study, we aim to identify risk factors for ventricular septal defects (VSDs) in Northwest Russia. The study population included singleton births registered in the Murmansk Co…
Adverse Pregnancy Outcomes among Adolescents in Northwest Russia
This study aimed to assess whether adolescents have an increased risk of adverse pregnancy outcomes (APO) compared to adult women. We used data on 43,327 births from the population-based Arkhangelsk County Birth Registry, Northwest Russia, for 2012-2014. The perinatal outcomes included stillbirth, preterm birth (<37 and <32 weeks), low and very low birthweight, 5 min Apgar score <7 and <4, perinatal infections, and the need for neonatal transfer …
Prenatal Exposure to Aluminum and Status of Selected Essential Trace Elements in Rural South African Women at Delivery
This study sought to evaluate the in utero exposure to aluminum and status of selected trace elements in South African women at delivery since aluminum is known to be toxic in all developmental stages even at low concentrations. Serum aluminum was negatively correlated with aluminum in urine, both uncorrected and corrected for creatinine, which suggests the retention of aluminum in body stores. Serum copper and zinc levels were found to be high i…
Risk factors for perinatal mortality in Murmansk County, Russia
BACKGROUND: Factors contributing to perinatal mortality (PM) in Northwest Russia remain unclear. This study investigated possible associations between selected maternal and fetal characteristics and PM based on data from the population-based Murmansk County Birth Registry. OBJECTIVE: This study investigated possible associations between selected maternal and fetal characteristics and PM based on data from the population-based Murmansk County Birt…
Effect of Smoking Behavior before and during Pregnancy on Selected Birth Outcomes among Singleton Full-Term Pregnancy
The aim of our study was to assess associations between smoking behavior before and during pregnancy and selected adverse birth outcomes. This study is based on the Murmansk County Birth Registry (MCBR). Our study includes women who delivered a singleton pregnancy after 37 weeks of gestation (N = 44,486). Smoking information was self-reported and assessed at the first antenatal visit during pregnancy. We adjusted for potential confounders using l…
Do Cervical Cancer Patients Diagnosed with Opportunistic Screening Live Longer? An Arkhangelsk Cancer Registry Study
The aim of the current study was to compare cervical cancer (СС) patients diagnosed with and without screening in terms of: (i) sociodemographic and clinical characteristics; (ii) factors associated with survival; and (iii), and levels of risk. A registry-based study was conducted using data from the Arkhangelsk Cancer Registry. It included women with newly diagnosed malignant neoplasm of the uterine cervix during the period of 1 January 2005 to …
Arkhangelsk County Birth Registry as an Inportant Source of Information for Research and Healthcare
The article presents a short review of already established birth registries worldwide and their value for public health and perinatal medicine. Implementation of Arkhangelsk County Birth Registry (ACBR) is presented in detail. Paper registration form contains information on maternal pre-pregnancy and pregnancy health status, reproductive history, data on folic acid and multivitamin intake as well as alcohol consumption and tobacco smoking before …
Gestation-Specific Live-Born Twin Birth Weight, Length and Head Circumference Percentiles and Curves Adapted for North-Western Russia
Until now, national percentiles and curves for twins based on population registry data have not been published. It complicates the diagnosis of fetal growth retardation. In the article, the algorithms of birth weight, length and head circumference percentiles and curves for twins born alive at gestational age 32-40 weeks are described. We used data from the population-based Murmansk County Birth Registry (2006-2011) and the Arkhangelsk County Bir…
Gestation-Specific Live-Born Singleton Newborns Birth Weight, Length and Head Circumference Percentiles and Curves (Arkhangelsk County Birth Registry Data)
Birth weight, length and head assessment are important for postnatal confirmation of fetal growth retardation. In Russia, there has so far not been sex-specific, population-based birth weight, length and head circumference percentiles and curves for singleton newborns. The aim of this study was to develop percentiles and curves for live-born newborns born at 28-42 weeks of gestation and compare these to other available data from the literature. D…
Climate change and the potential effects on maternal and pregnancy outcomes
In 2007, the Intergovernmental Panel on Climate Change (IPCC) presented a large amount of evidence about global warming and the impact of human activities on global climate change. The Lancet Commission have identified a number of ways in which climate change can influence human health: lack of food and safe drinking water, poor sanitation, population migration, changing disease patterns and morbidity, more frequent extreme weather events, and la…
Arkhangelsk County Birth Registry as an Inportant Source of Information for Research and Healthcare
The article presents a short review of already established birth registries worldwide and their value for public health and perinatal medicine. Implementation of Arkhangelsk County Birth Registry (ACBR) is presented in detail. Paper registration form contains information on maternal pre-pregnancy and pregnancy health status, reproductive history, data on folic acid and multivitamin intake as well as alcohol consumption and tobacco smoking before …
A Call for Urgent Monitoring of Food and Water Security Based on Relevant Indicators for the Arctic
This perspective paper argues for an urgent need to monitor a set of 12 concrete, measurable indicators of food and water security in the Arctic over time. Such a quantitative indicator approach may be viewed as representing a reductionist rather than a holistic perspective, but is nevertheless necessary for actually knowing what reality aspects to monitor in order to accurately understand, quantify, and be able to project critical changes to foo…
The prevalence of selected pregnancy outcome risk factors in the life-style and medical history of the delivering population in north-western Russia
Compared with the delivering population in Norway, that in Moncegorsk was younger and had a lower prevalence of obesity, diabetes and heavy smoking. The most worrisome findings were the high prevalence of a history of abortion and PID. A relatively high proportion of the women worked in physically demanding, or/and nickel-exposed occupations
Indications of decreasing human PTS concentrations in North West Russia
BACKGROUND: The Russian Arctic covers an enormous landmass with diverse environments. It inhabits more than 20 different ethnic groups, all of them with various living conditions and food traditions. Indigenous populations with a traditional way of living are exposed to a large number of anthropogenic pollutants, such as persistent organic pollutants (POPs) and toxic metals, mainly through the diet. Human monitoring of persistent organic pollutan…
Climate change and the potential effects on maternal and pregnancy outcomes
In 2007, the Intergovernmental Panel on Climate Change (IPCC) presented a large amount of evidence about global warming and the impact of human activities on global climate change. The Lancet Commission have identified a number of ways in which climate change can influence human health: lack of food and safe drinking water, poor sanitation, population migration, changing disease patterns and morbidity, more frequent extreme weather events, and la…
A Call for Urgent Monitoring of Food and Water Security Based on Relevant Indicators for the Arctic
This perspective paper argues for an urgent need to monitor a set of 12 concrete, measurable indicators of food and water security in the Arctic over time. Such a quantitative indicator approach may be viewed as representing a reductionist rather than a holistic perspective, but is nevertheless necessary for actually knowing what reality aspects to monitor in order to accurately understand, quantify, and be able to project critical changes to foo…
Risk factors for perinatal mortality in Murmansk County, Russia
BACKGROUND: Factors contributing to perinatal mortality (PM) in Northwest Russia remain unclear. This study investigated possible associations between selected maternal and fetal characteristics and PM based on data from the population-based Murmansk County Birth Registry. OBJECTIVE: This study investigated possible associations between selected maternal and fetal characteristics and PM based on data from the population-based Murmansk County Birt…
Effect of Smoking Behavior before and during Pregnancy on Selected Birth Outcomes among Singleton Full-Term Pregnancy
The aim of our study was to assess associations between smoking behavior before and during pregnancy and selected adverse birth outcomes. This study is based on the Murmansk County Birth Registry (MCBR). Our study includes women who delivered a singleton pregnancy after 37 weeks of gestation (N = 44,486). Smoking information was self-reported and assessed at the first antenatal visit during pregnancy. We adjusted for potential confounders using l…
Do Cervical Cancer Patients Diagnosed with Opportunistic Screening Live Longer? An Arkhangelsk Cancer Registry Study
The aim of the current study was to compare cervical cancer (СС) patients diagnosed with and without screening in terms of: (i) sociodemographic and clinical characteristics; (ii) factors associated with survival; and (iii), and levels of risk. A registry-based study was conducted using data from the Arkhangelsk Cancer Registry. It included women with newly diagnosed malignant neoplasm of the uterine cervix during the period of 1 January 2005 to …
Arkhangelsk County Birth Registry as an Inportant Source of Information for Research and Healthcare
The article presents a short review of already established birth registries worldwide and their value for public health and perinatal medicine. Implementation of Arkhangelsk County Birth Registry (ACBR) is presented in detail. Paper registration form contains information on maternal pre-pregnancy and pregnancy health status, reproductive history, data on folic acid and multivitamin intake as well as alcohol consumption and tobacco smoking before …
Gestation-Specific Live-Born Twin Birth Weight, Length and Head Circumference Percentiles and Curves Adapted for North-Western Russia
Until now, national percentiles and curves for twins based on population registry data have not been published. It complicates the diagnosis of fetal growth retardation. In the article, the algorithms of birth weight, length and head circumference percentiles and curves for twins born alive at gestational age 32-40 weeks are described. We used data from the population-based Murmansk County Birth Registry (2006-2011) and the Arkhangelsk County Bir…
Gestation-Specific Live-Born Singleton Newborns Birth Weight, Length and Head Circumference Percentiles and Curves (Arkhangelsk County Birth Registry Data)
Birth weight, length and head assessment are important for postnatal confirmation of fetal growth retardation. In Russia, there has so far not been sex-specific, population-based birth weight, length and head circumference percentiles and curves for singleton newborns. The aim of this study was to develop percentiles and curves for live-born newborns born at 28-42 weeks of gestation and compare these to other available data from the literature. D…
Risk Factors for Ventricular Septal Defects in Murmansk County, Russia
Cardiovascular malformations are one of the most common birth defects among newborns and constitute a leading cause of perinatal and infant mortality. Although some risk factors are recognized, the causes of cardiovascular malformations (CVMs) remain largely unknown. In this study, we aim to identify risk factors for ventricular septal defects (VSDs) in Northwest Russia. The study population included singleton births registered in the Murmansk Co…
Adverse Pregnancy Outcomes among Adolescents in Northwest Russia
This study aimed to assess whether adolescents have an increased risk of adverse pregnancy outcomes (APO) compared to adult women. We used data on 43,327 births from the population-based Arkhangelsk County Birth Registry, Northwest Russia, for 2012-2014. The perinatal outcomes included stillbirth, preterm birth (<37 and <32 weeks), low and very low birthweight, 5 min Apgar score <7 and <4, perinatal infections, and the need for neonatal transfer …
Prenatal Exposure to Aluminum and Status of Selected Essential Trace Elements in Rural South African Women at Delivery
This study sought to evaluate the in utero exposure to aluminum and status of selected trace elements in South African women at delivery since aluminum is known to be toxic in all developmental stages even at low concentrations. Serum aluminum was negatively correlated with aluminum in urine, both uncorrected and corrected for creatinine, which suggests the retention of aluminum in body stores. Serum copper and zinc levels were found to be high i…
An Increased Risk of Stunting among Newborns in Poorer Rural Settings
We conducted an observational study of 194 pregnant women from two different study sites in rural Cambodia. Socioeconomic and anthropometric data was obtained from the women and their newborns. In addition, we collected blood and urine samples from the women for further analyses in planned papers. There were significant differences between the two study groups for clinical outcomes. The mothers from the poorer area were shorter and weighed less a…
Incidence and Risk Factors of Pre-Eclampsia in the Paropakar Maternity and Women’s Hospital, Nepal
This study aims to determine the incidence of pre-eclampsia and distribution of risk factors of pre-eclampsia at Paropakar Maternity and Women's Hospital, Kathmandu, Nepal. A retrospective study included 4820 pregnant women from 17 September to 18 December 2017. Data were obtained from the medical records of the hospital's Statistics Department. Associations between the risk factors and pre-eclampsia were determined using logistic regression anal…
Health Risk Modifiers of Exposure to Persistent Pollutants among Indigenous Peoples of Chukotka
The aim of the study was to assess temporal trends in health risks related to most common persistent contaminants, including polychlorinated biphenyls (PCBs), dichloro-diphenyl-trichloroethanes (DDTs), lead (Pb), as well as mercury (Hg) among indigenous peoples living in coastal areas of Chukotka in Arctic Russia. This is examined in relation to exposure pathways and a range of social and behavioral factors capable of modifying the exposure to th…
The Role of Leptin Levels in Adaptation to Cold Climates
Currently, adipose tissue is considered an endocrine organ that produces hormone-active substances, including leptin, which can play a key role in thermoregulation processes. Therefore, we performed a meta-analysis to investigate the influence of the climatic environment on leptin levels. A systematic literature search in the databases was carried out on 10 January 2020. Finally, 22 eligible articles were included in the current meta-analysis and…
In Utero Exposure to Aluminium and Other Neurotoxic Elements in Urban Coastal South African Women at Delivery
Aluminium (Al) is a non-essential neurotoxicant and there is limited information regarding exposure to Al in utero. This study sought to evaluate the in utero exposure to Al in urban South African women, its effects on birth outcomes and possible synergistic effects between Al, essential and neurotoxic elements such as lead (Pb), mercury (Hg) and arsenic (As), as well as a a potential sex-dependent response to these elements in neonates. This stu…
Serum Concentrations of Selected Organochlorines in Pregnant Women and Associations with Pregnancy Outcomes. A Cross-Sectional Study from Two Rural Settings in Cambodia
We conducted a cross-sectional study among 194 pregnant women from two low-income settings in Cambodia. The inclusion period lasted from October 2015 through December 2017. Maternal serum samples were analyzed for persistent organic pollutants (POPs). The aim was to study potential effects on birth outcomes. We found low levels of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCP), except for heptachlors, β-hexachlorocyclohexane…
Selenium Status, Its Interaction with Selected Essential and Toxic Elements, and a Possible Sex-Dependent Response In Utero, in a South African Birth Cohort
Selenium (Se) is an essential trace element and its deficiency in utero may affect fetus development and birth outcomes. The current study aimed to assess serum Se status at delivery and examine the possible association between Se levels and birth outcomes. The interaction of Se with selected essential and toxic elements as well as possible sex-dependent responses in utero were also evaluated. The negative association between Se levels and head c…
Emergency Craniotomy and Burr-Hole Trephination in a Low-Resource Setting
To evaluate the teaching effect of a trauma training program in emergency cranial neurosurgery in Cambodia on surgical outcomes for patients with traumatic brain injury (TBI). We analyzed the data of TBI patients who received emergency burr-hole trephination or craniotomy from a prospective, descriptive cohort study at the Military Region 5 Hospital between January 2015 and December 2016. TBI patients who underwent emergency cranial neurosurgery …
Experiences of Using Misoprostol in the Management of Incomplete Abortions
Complications after abortion are a major cause of maternal death. Incomplete abortions are common and require treatment with surgical or medical uterine evacuation. Even though misoprostol is a cheaper and safer option, it is rarely used in Malawi. To improve services, an intervention was performed to increase the use of misoprostol in post-abortion care. This study explored healthcare providers' perceptions and experiences with misoprostol in th…
Geographic and Ethnic Variations in Serum Concentrations of Legacy Persistent Organic Pollutants among Men in the Nenets Autonomous Okrug, Arctic Russia
The overwhelming majority of Arctic biomonitoring studies in humans include either pregnant or non-pregnant women of reproductive age while little attention is paid to toxic compounds concentrations in men. This study contributes with information of the present amounts of persistent organic pollutants (POPs) in men living in Arctic Russia. We studied the serum concentrations of 11 polychlorinated biphenyl (PCB) congeners and 17 organochlorine pes…
Maternal Blood Levels of Toxic and Essential Elements and Birth Outcomes in Argentina
Pregnant women's levels of toxic and essential minerals have been linked to birth outcomes yet have not been adequately investigated in South America. In Argentina, n = 696 maternal whole blood samples from Ushuaia ( n = 198) and Salta ( n = 498) were collected in 2011-2012 among singleton women at 36 ± 12 h postpartum and analyzed for blood concentrations of arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), copper (Cu), manganese (Mn), seleni…
Investigating the relationship between non-occupational pesticide exposure and metabolomic biomarkers
The relationship between pesticide exposures and metabolomics biomarkers is not well understood. We examined the changes in the serum metabolome (early biomarkers) and the metabolic pathways associated with various pesticide exposure scenarios (OPE: overall exposure, PEM: exposure in months, PEY: exposure in years, and PEU: reported specific pesticides use) using data from the Northern Finland Birth Cohort 1966 31-year cross-sectional examination…
Medicine (24 obras) · Pregnancy (19 obras) · Obstetrics (15 obras) · Environmental health (14 obras) · Population (14 obras) · Biology (12 obras) · Heavy Metal Exposure and Toxicity (8 obras) · Internal Medicine (7 obras) · Birth weight (6 obras) · Chemistry (6 obras)