1. Introduction

Natural fertility regulation (NFR) methods could provide family planning (avoiding or achieving pregnancy) naturally through conforming to the women’s reproductive cycle without the use of drugs or devices. NFR originated about 60 years ago from the rhythmic method, but this method was not scientifically based. Its deadly shortcoming is the prediction of the coming events on the basis of the past rhythm and is therefore destined to be inaccurate with a failure rate of more than 20%. A milestone in the NFR study is the discovery of the intrinsic relationship between the cervical mucus, the hormonal balance and the fertility status of women by the Billings group. It was shown that the changes in the cervical mucus correlated with the sex hormone levels in the women, 1,2 thus, the fertile status could be determined by observing the characteristics of the cervical mucus at the vulva. 3,4 In this way the Billings Ovulation Method® (BOM) overcomes the fatal weakness of early natural family planning methods in predicting the current events on the basis of past happening, and lays the foundation of scientific NFR research.

There have been many reports on Billings Ovulation Method® field trials all over the world. 5-11 They all reached a common conclusion, i.e., the Billings Ovulation Method® had a very low method-related pregnancy rate and a consistently high continuation rate. Since the preliminary trial of the Billings Ovulation Method® in China in 1990 and the official introduction of the method by the Chinese Ministry of Health in 1995, the Method has been widely used in China both for avoiding and achieving pregnancy with promising results. 12-16

2. Design and Methodology

In China the Billings Ovulation Method® has been used in more than 156,400 fertile couples for avoiding pregnancy and 3,268 infertile couples for achieving pregnancy. In well-designed field trials we studied the Billings Ovulation Method® and an intrauterine device in avoiding pregnancy. In these trials we paid much attention to the following items:

2.1 Qualified Teachers. The Billings teachers (nurses or midwives) had themselves been trained and examined by authenticated Chinese and Australian (during site visits) doctors. Only those who obtained good scores were awarded the certificate of “Billings teacher”. In the majority of cases, the teachers were married young women with a long experience of using the Billings Ovulation Method® for the avoidance of pregnancy.

2.2 Competent Teaching Course. All women accepting the Billings Ovulation Method® were trained by weekly interviews for 1 month under the supervision of Billings teachers. In the training, in addition to the principal Billings Ovulation Method® knowledge, the following key points were stressed: (a) Mucus Symptoms. The identification of mucus depends mainly on the vulval sensation and to a lesser extent on its appearance; in some women no mucus may be seen and the only signs of the fertile days or the beginning of the fertile days are a wet/slippery sensation and a soft and swollen vulva. (b) The Early Day Rules and the Peak Rule should be strictly observed. If the Peak symptoms are not clear (no slippery/lubricative sensation at the vulva), one should continue to follow the Early Day Rules.

2.3 Subject-screening Procedure. After the training, every subject was interviewed to see whether she could proficiently master the Billings Ovulation Method®. Those who could not identify the mucus symptoms were either allocated a special tutor to help them or screened out. This measure was intended to ensure everybody participating in the study mastered the Billings Ovulation Method®.

2.4 On-the-Spot Guidance and Regular Follow-up Visits. During the trial a teacher was assigned to take care of 20 women as their on-the-spot guide. Arrangement was made so that women could get in touch with the teacher at any time they wished. The responsible teacher should be clearly aware of the cycle pattern, in particular the fertile days of every woman they guided. The principal investigator of the centre interviewed the volunteers biweekly (every other visit as arranged by the responsible teacher) in the first 2 months and then monthly (at the time of changing mucus symptoms) to check their personal record, monitor the women’s comprehension of the rules, and reinforce their motivation and spousal support (husbands were invited to participate in every other visit). At the end of the 2 months the responsible teacher and the principal investigator could decide that the couples were now autonomous. The woman not available for follow-up interviews for three consecutive times was considered lost to follow-up. It is generally accepted that the acquisition of Billings Ovulation Method® knowledge by the participants, the women’s motivation and the husbands’ cooperation are the key points for the successful implementation of the Billings Ovulation Method®. Our programme not only imparted scientific knowledge but also provoked and maintained the initiative of the women and their husbands. Thus, the result of the present study is highly rational and reflective of the scientific essence of the Billings Ovulation Method®.