You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["HealthCareActivity", "InjuryOrPoisoning", "BodySubstance", "IntellectualProduct", "AnatomicalStructure", "SpatialConcept", "Chemical", "Bacterium", "MedicalDevice", "Organization", "BiomedicalOccupationOrDiscipline", "Finding", "BiologicFunction", "Virus", "ResearchActivity", "ClinicalAttribute", "PopulationGroup", "Eukaryote", "BodySystem", "Food", "ProfessionalOrOccupationalGroup"].

Please return the output as a JSON object of the format: {"Virus": ["HIV", ...], "Bacterium": ["MRSA", ...], "AnatomicalStructure": ["Lung", ...], "BodySystem": ["CNS", ...], "BodySubstance": ["Serum", ...], "Finding": ["Headache", ...], "InjuryOrPoisoning": ["Fracture", ...], "BiologicFunction": ["Death", ...], "HealthCareActivity": ["Biopsy", ...], "ResearchActivity": ["Clinical trial", ...], "MedicalDevice": ["Lenses", ...], "SpatialConcept": ["Camps", ...], "BiomedicalOccupationOrDiscipline": ["Forensic medicine", ...], "Organization": ["WHO", ...], "ProfessionalOrOccupationalGroup": ["Provider", ...], "PopulationGroup": ["Swimmers", ...], "Chemical": ["Gold", ...], "Food": ["Rice", ...], "IntellectualProduct": ["RPAM", ...], "ClinicalAttribute": ["Biomarker", ...], "Eukaryote": ["Dogs", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Maternal vitamin D levels and the risk of perinatal death To determine the association between maternal vitamin D levels and perinatal death. A retrospective cross-sectional study of all non-anomalous, singleton births (≥24 weeks) with perinatal death compared to a matched control group. Only pregnancies with a recorded vitamin D level at booking (8-19 weeks gestation) were included for analysis. Maternal vitamin D levels were categorized into normal, deficient and insufficient cohorts and variables compared between the three groups. There were 31 perinatal deaths which were compared to 111 controls. Median vitamin D levels were lower in the perinatal death cohort compared to the control group (55 nmol/L versus 64 nmol/L, p = 0.43). There was no significant increase in deaths between the normal and deficient (p = 0.33) or insufficient (p = 0.09) groups. Low maternal vitamin D levels at booking were not associated with an increased risk of perinatal demise.
{"AnatomicalStructure": [], "Bacterium": [], "BiologicFunction": ["pregnancies", "perinatal demise", "perinatal death", "deaths", "births", "perinatal deaths", "gestation"], "BiomedicalOccupationOrDiscipline": [], "BodySubstance": [], "BodySystem": [], "Chemical": ["vitamin D"], "ClinicalAttribute": [], "Eukaryote": [], "Finding": [], "Food": [], "HealthCareActivity": [], "InjuryOrPoisoning": [], "IntellectualProduct": [], "MedicalDevice": [], "Organization": [], "PopulationGroup": ["groups", "cohorts", "cohort"], "ProfessionalOrOccupationalGroup": [], "ResearchActivity": ["cross-sectional study", "analysis"], "SpatialConcept": [], "Virus": []}