More specifically, couples should
- Stop having intercourse as soon as "less fertile" cervical fluid starts.
- Start having intercourse only after 4 days with ALL of the following
- Increased temperature indicating ovulation.
- "Less fertile" cervical fluid or no cervical fluid.
- Hard, closed cervix.
- Not have intercourse if they aren't sure what they are observing.
One of the interesting aspects of natural family planning is that it doesn't assume a goal - many couples use NFP to increase the likelihood of pregnancy (in fact, using NFP to achieve pregnancy is probably more mainstream!), and many couples who use NFP to avoid pregnancy also use it to achieve pregnancy when they want children. NFP also gives couples flexibility in determining their chances of getting pregnant - a couple using NFP to space children may decide to only follow the rules loosely, perhaps by waiting for "more fertile" cervical fluid before ceasing intercourse, while a couple that strongly wants to avoid pregnancy for several years may be very conservative when applying the rules.