If you have a new baby and you already had estate planning documents completed when your first child was born, there's no need to re-do everything. But you still need to review the estate plan.
In the post "Will another baby affect your current will?"New Jersey 101.5 advises checking on your will to see whether it identifies your "children" or "descendants" as your beneficiaries—and then defines those terms to provide that children born after you executed your will are included.
If it does, then it is probably not urgent to update your will to include your new child's name. However, if the will was drafted without that flexibility and only identifies your first child by name as the beneficiary, then you need to talk with your estate planning attorney and have your will updated.
While you're at it, review your beneficiary designations for your life insurance policies and retirement plans. In those documents, you may have named your first child specifically as a beneficiary. If so, an update may be necessary.
Also, be careful of naming your estate as the beneficiary of any retirement assets. If you do, it can have unintended adverse income tax consequences after your death.
If you have significant retirement assets and want to name as beneficiaries of those assets any trusts under your will for the benefit of your children, consult with a knowledgeable trust and estate attorney who can counsel you regarding any required revisions to your will and retirement account beneficiary designations.
Reference: New Jersey 101.5 (January 12, 2016) "Will another baby affect your current will?"