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: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. 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:

The efficacy of metformin in pregnant women with polycystic ovary syndrome: a meta-analysis of clinical trials. Objectives: The role of metformin in the treatment of pregnant women with polycystic ovary syndrome is controversial. Therefore, we evaluated whether the use of metformin during pregnancy in women with polycystic ovary syndrome could reduce pregnancy-related complications. Research design and methods: MEDLINE was searched to retrieve relevant trials. In addition, reviews and reference lists of the retrieved articles were scanned for further appropriate studies. The primary outcome measure was the incidence of complications of pregnancy, which included early pregnancy loss, gestational diabetes, preeclampsia and preterm delivery. Results: In total, eight studies with 1106 patients were included. The pooled ORs (95% CIs) of outcome for pregnant women with polycystic ovary syndrome prescribed metformin were 0.32 (0.19-0.55) for early pregnancy loss, 0.37 (0.25-0.56) for gestational diabetes, 0.53 (0.30-0.95) for preeclampsia and 0.30 (0.13-0.68) for preterm delivery. Conclusions: Metformin therapy throughout pregnancy decreased the ORs of early pregnancy loss, gestational diabetes, preeclampsia and preterm delivery in pregnant PCOS women with no serious detrimental sideeffects.
{"Chemical": ["Metformin", "metformin"]}