Natural Family Planning (NFP) is fertility awareness. A couple can then use that knowledge to either postpone or to help achieve a pregnancy. Barring any problems, men are always fertile.
Women go through phases of fertility and infertility. Modern methods of NFP teach you to identity these phases of fertility. When used correctly, NFP is 99% effective in postponing pregnancy.
The Diocese has NFP resources available on their website for anyone looking for help or support.