A prenuptial agreement can offer excellent protections and detailed guidance, provided the couple who creates it does so with a nuanced understanding of the legal issues at hand. If an agreement includes stipulations surrounding child support or child custody, a court will almost certainly toss out at least the relevant provisions, and possibly the entire agreement, leaving couples with many fewer protections than they expected.
The law does not allow prenuptial agreements to include terms surrounding child support, because it is not up to parents to determine their own level of obligation to a child. Child support is a legal right of the child that the court enforces, not a privilege of a parent.
Likewise, courts do not allow prenuptial agreements to include stipulations around child custody, to protect both the parents and the child. Ideally, a court does prefer for parents to work together to create a parenting plan and custody agreement that suits all parties needs, but it is primarily concerned with protecting the best interests of the child. Not only may prenuptial agreement terms around child custody create disadvantageous circumstances for the child, they may deny one parent or the other important parental rights that were not considered clearly when creating or signing the agreement.
As you create your prenuptial agreement, be sure to understand the legal issues at hand in detail. An experienced attorney is an excellent resource of nuanced guidance through these issues, and can help ensure that your agreement truly protects and represents both spouses' interests and concerns, while working within the confines of the law.
Source: FindLaw, "What Can and Cannot be Included in Prenuptial Agreements," accessed March 02, 2018