It is likely that once you bring a child into this world you are going to be more concerned about them than you are about yourself which means you need a will as Nerdwallet explains in "Protect Your Family by Writing a Will."
Parents who want to make sure their children are taken care of if the parents pass away need a will. Two important things can be done with a will. First, in a will parents can make sure their children are taken care of financially. Second, and most importantly, a will is the proper legal document for parents to express their wishes about who should act as guardians for their minor children.
The guardian is the person tasked with taking care of the day-to-day needs of the child. Parents who want to have a say in who rears their children thus need to have a will.
There are other estate planning documents that can be helpful for parents with young children.
An estate planning attorney can guide you through the process of best matching an estate plan with your circumstances.
Reference: Nerdwallet (Sept. 19, 2016) "Protect Your Family by Writing a Will."