ABSTRACT
Any disturbance or change from normal routine could affect the indicators of fertility or disrupt the menstrual cycle. A disturbance can vary in its effects from disrupting a single temperature reading to affecting the menstrual cycle in its entirety. Each woman’s response to disturbances will vary. Women should be encouraged to note any disturbances on the chart, either in the comments box or next to the affected reading. A number of common disturbances affect specific indicators: for example, alcohol is likely to cause a raised temperature and antihistamines will dry cervical secretions. These factors are discussed fully in the relevant chapter covering the specific fertility indicator, with a summary on page 224. Disrupted charts may not be interpretable. If the guidelines cannot be applied, the chart should be clearly marked “ uninterpretable ” ( figure 12.5 ). A couple who are avoiding pregnancy should be advised to consider themselves potentially fertile until the situation becomes clear. There are some circumstances where FAMs cannot be relied upon – either because a medical condition makes it impossible to accurately interpret the fertility indicators or because pregnancy is strongly contraindicated (for example, during chemotherapy) – see restrictions on the use of FAMs for avoiding pregnancy on page 362.
