PIP: There is renewed interest in natural family planning (NFP) as the Philippine Population Program enters the 1980s. Much of this interest is due to the realization that, properly practiced, NFP can be a highly effective means of birth spacing. In 1978 the Special Committee to Review the Philippine Population Program recommended that more efforts be made to promote NFP. The different methods of NFP are reviewed. Sex without intercourse, coitus interruptus, and prolonged nursing are not officially recognized as NFP methods by the Program. The rhythm method was first described independently by Drs. Hermann Knaus of Austria and Kyusaku Ogino of Japan in the 1930s. Ogino's method of calculating a woman's fertile period is based on the lengths of the last 12 menstrual cycles which she recorded on a calendar. The advantages of rhythm are that it is inexpensive, it requires only the cost of charts which may be homemade, there are no physical side effects, control is in the woman's hands, and it is acceptable to people who consider it their duty to follow religious teachings. Disadvantages include: keeping constant, accurate records of cycles for long periods of time; the need for perseverance and correct interpretation of the chart; the possible need for medical advice and help; and the fear that something might upset a woman's cycle and change the time of ovulation. The continuation rates of rhythm acceptors in the Philippines are unimpressive. A study of 142 women revealed a high pregnancy/failure rate--25% for a 12-month period compared to 0 with oral contraception (OC) and the IUD's 2%. The basal body temperature method helps determine the unsafe period with some accuracy. Its premise is that there are slight but detectable changes in a woman's body temperature during her cycle. These changes herald ovulation. A special thermometer must record temperature changes of 0.1 degree Farenheit. This instrument and the charts are the only expenses involved. The reviewers of the Philippine Population Program noted that since the end of the unsafe period can be indicated only by the temperature, the total period of abstinence becomes long, although the basal body temperature method gives more or less 10 successive days for intercourse. The cervical mucus method, also known as the Billings method, takes into account the cervical secretions during the menstrual cycle. Appearance of this mucus is an indication of fertility. All that is required of a practitioner is to learn to distinguish the different sensations of wetness and dryness. The disadvantage is that the method becomes ineffective in areas where there is cervicitis or infection of the cervix. The symptom thermal method is the basal body temperature method combined with other NFP techniques and is widely used. With this method an accurate record of the 6 immediately preceding menstrual cycles is established. The start of the fertile period is set by substracting 20 days plus 1. The woman watches for symptoms like pelvic heaviness, breast softness, and mucus discharge.