All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, it is not permissible for the family of the husband to interfere between him and his wife in order to spoil their marital relationship. Indeed, Allaah advised us to reconcile between them when dissension occurs; Allaah Says (what means): {If you fear a breach between them twain (the man and his wife), appoint (two) arbitrators, one from his family and the other from hers; If they both desire reconciliation, Allaah will cause it between them. Indeed Allaah is Ever All-Knower. Well-Acquainted with all things.}[Quran 4:35] Therefore, interfering between the husband and his wife in order to spoil the relationship between them is contrary to the Sharee’ah. Furthermore, the parents of the husband are not permitted to order him to divorce his wife and he is not obliged to obey them in this regard if they have no sound reason for this, like if the wife whom they ask him to divorce is corrupt in her religion and moral conduct, and it was not possible to rectify her.
Indeed, they were wrong in giving you the choice between giving them the child after birth and divorce (while taking child support), and you did well by not agreeing to anything of that. Divorce is in the hands of the husband and not in the hands of his parents.
If your husband has no sound excuse for not being concerned about you and not contacting you when you were at the hospital, then he is also wrong. Therefore, we advise you to endeavour to look for him and meet him, or contact him in order to have a mutual understanding with him. Indeed, he has the choice between two things which Allaah mentioned in His Book. Allaah Says (what means): {Either you retain her on reasonable terms or release her with kindness.}[Quran 2:229]
Then, if you are unable to find him, or that you found him but you were unable to solve the problem with him, then you should take the matter to the authority that looks into the affairs of the Muslims in your country so that they would study the case and remove the harm off you.
As regards his first wife, it is not strange that she behaves in this way towards you (as a second wife of her husband). However, she is undoubtedly not permitted to harm you with such provocations or to threaten you that your husband will divorce you.
Hence, we advise you to be patient with her, and if you can change your phone number then do so, so that she will not be able to contact you.
Finally, your husband is obliged to be just between you and her in providing for both of you and in spending the night with you equally. it is an obligation on the husband to be just between his two wives as long as one of them does not renounce her right as explained in Fatwa 90663.