Natural family planning (NFP) methods can be effective if taught well and practised by well-motivated couples. Midwives should be able to give couples an understanding of the basic principles of the methods. The observable signs of the fertile cycle are changes in basal body temperature, in the consistency of cervical mucus and in the texture and position of the cervix. Practised properly the ovulation method can have a failure rate of as little as 2.2 pregnancies per 100 woman-years. The ovulation method is a suitable method for mothers who have breastfed to detect the onset of ovulation.