Sister's concern

It’s a situation about my elder sister who did love cum arrange marriage four years & four months ago. Her husband use to harass her by physically and mentally. Between I want to enlighten about her, as she is the topper during school and collage days, she has done BA, MA, M.Ed., MBA & Mphill. And working in reputed firm. Her salary goes to her husband’s EMI and loan that he borrowed on her credit cards. Her husband use to come at our home and ask for dowry, threat to my family and abuse, many times he tried to punch to my parents. He calls & text message to other family members’ unnessarsirly & me. Now at this time, my sister is 5 months pregnant, he does not care her and never allow her to talk to the family members. He does use so pathetic words, which can’t be listened. We do not know, what has he done to our sister, she just bear all this and cry but never boost her mind to file a report against him. Even whole family told to the daughter “ Beta you just stand with us, so we may file a report against him” but she does not utter a word. We do not know what would happen to our sister, my parents are old and sugar patient. Please advice us, What should we do to save our sister. Looking Forward Brother