When it comes to children, we want to make sure that we view them as God intended: as his blessings (Psalm 127:3-5). If a Christian husband and wife are physically able to have children and choose not to have children, they will need to examine their motives and methods to see how those line up with God’s word. Reasons for not wanting to have children might include concerns for the physical, emotional or mental state of one or both spouses.
Christian Life Resources, a WELS-affiliated ministry, has good resources on this subject. I encourage you to read especially the three-part series on birth control. God’s blessings to you.