Funded by the UNFPA and IPHD

Researchers: William M. Pruzensky, Ph.D.

Susan Langley


This research study of modern natural family planning (NFP) methods was carried out by the IPHD (International Partnership for Human Development) in four Latin American countries (Brazil, Dominican Republic, Ecuador, and El Salvador) in order to determine the effectiveness and the length of time women used their chosen modern NFP method following the time point they reached autonomy from a teacher(s), referred to as the end of the learning period, and to compare continuation rates with those found in other NFP studies worldwide. Most studies of NFP effectiveness and continuation rates following autonomy were undertaken mainly in the developed world, and in Africa. The study would fill a gap in knowledge about the length of time women use modern methods of natural family planning after the learning period, and about the conditions under which continuation and effectiveness rates may be highest in Latin America.

The long-term objective was to show that continuation rates of using modern natural family planning (NFP) methods are sustainable for at least 12-18 months after women users were successfully taught a modern natural method of contraception, and that rates were comparable to the Mauritius study, as well as with other studies, of women using modern NFP methods for one year or more. The immediate objectives were to calculate the percentage of women who switched to a modern non-natural or artificial method of family planning by the 12th to 18th month after being taught to use a modern NFP method successfully, and to learn why and when they decided to switch, and secondly, to show what percentage of adolescents taught a modern NFP method discontinued NFP use or switched to other family planning methods 12 to 18 months after becoming autonomous NFP method users. Nonetheless, the main focus of this study was to assess continuation rates of NFP users: rates of unplanned pregnancies and method switching being only two factors that have a bearing on the calculation of these rates.

The four NFP programs selected for the study represented a cross-section of modern NFP services in Latin America. Program size, resources, teaching approaches and methods, geographical location, and data collection and analysis experiences differed to some extent. The four NFP service programs selected were the following:

(a)National Confederation of Natural Family Planning Centers (CENPLAFAM), Brazil.

(b)National Commission on the Family Pastoral, Dominican Repub­lic.

(c)NFP Program of the Archdiocese of Cuenca, Ecuador.

(d)Association of Ovulation Method Billings (AMOBES), El Salva­dor.

Three of the four NFP programs had participated in the IFFLP (International Federation for Family Life Promotion) data improve­ment and management project, supported by an A.I.D. sub-contract from the Institute for Reproductive Health, Georgetown University.

A questionnaire was developed by the IPHD and pilot-tested in all four Latin American countries. It was modified and re-tested several times. IPHD’s Senior Researcher visited each country three or four times to discuss key variables, to comb NFP user files and records, to guide the selection of NFP users to be studied, to select and help train interviewers, and to check data collected. A study size of 500-800 NFP users had been projected. Only women who had reached autonomy in NFP use 12 months prior to the interview period, October-December 1995 were selected. Most NFP users selected fell into the autonomy period of March-April to October 1994. The following final NFP user study size was selected for each participant NFP program/country:

Number of NFP

NFP Program/Country Autonomous Users

  • AMOBES: El Salvador 255
  • CENPLAFAM, Brazil 181
  • Family Pastoral, Dominican Republic 140
  • NFP Program, Ecuador (Cuenca) 105

     Total 681

The study analyzed the general characteristics of these NFP users. It showed that most modern NFP method users live in urban areas (63.58%). In fact, among Brazilian NFP users studied. 93.13% percent lived in urban areas. Only in the AMOBES El Salvador NFP program were there more rural NFP users (63.14%). It seems that costs, communication and follow up activities help determine whether an NFP program will be urban or rural-focused.

When program resources are scarce, NFP teachers cannot travel as often to rural areas. This results in reaching urban women, who are better educated and have higher incomes than rural women. In fact, except for the El Salvador NFP program, the mean level of education ranged from 9,210 years to 12.071 years. Only 53.60 percent of all users were housewives. Many were teachers (11.31%), secretaries (8.81%), or health workers, administrators, and small business women. The lowest number of housewives was in the Dominican Republic (39). The mean ages of the women studied ranged from 28.685 in Brazil to 32.286 in Ecuador. A total of 88.40 percent of the NFP users were married. Another 10.28 percent lived in free union. Others were separated or not living together. The Dominican Republic had the lowest number of married NFP users, 85.71 percent, and Brazil the highest percentage, 90.61 percent. Interestingly, 6.31 percent of the NFP users studied had a partner who had migrated to the United States or elsewhere after reaching autonomy. About 52 percent of all women studied had three or less pregnancies, and many were still in the stage of forming their family size. As expected, most NFP users were Catholics (95.89%).

In analyzing family planning experience, choice and intention, we found that over 45 percent of all autonomous NFP users studied had previously used another form of family planning, usually pills, IUDs, and calendar rhythm. In fact, 25.70 percent of the women studied had been oral contraceptive users. The percentage using pills was particularly high in Brazil (40.88%) and the Dominican Republic (30.00%). The largest number of former IUD users was found in Ecuador (26.67%). Other studies worldwide confirm that many NFP users had prior family planning experience. In some studies, over 50 percent of all women had used pills, IUDs or other family planning methods.

We found that most women who switched to modern NFP methods had a secondary to university education and were younger generally than non-switching women. Only 4.11 percent of the study group had previously used calendar rhythm. We had expected to find more women who used calendar rhythm switching to modern NFP methods. Most women became modern NFP method users because of health (37.89%) or religious (30.10%) reasons. Friends (26.28%) and clergy (25.26%) were instrumental in recruiting new NFP users, and pre-marriage courses ranked high for recruitment in Brazil (22.10%) and the Dominican Republic (23.57%).

Since the Ovulation Method (Billings Method) is the predominant method of modern NFP in Latin America, most (92.95%) understandably were OM users. Sympto-Thermal Method (STM) users were found only in Brazil (15.47%) and Ecuador (18.10%). Percentages are for their respective study groups. Women spacing births accounted for 53.01 percent of our study group, and women limiting births made up 46.99 percent. Limiters were predominant in Brazil (82.87%). Moreover, limiters tend to be older women, have more children, and generally tended to be former users of pills, IUDs and other artificial family planning methods. The study also learned that about 45 percent of the NFP users in the study changed their status one or more times after the learning period. This includes women who had unplanned and planned pregnancies, as well as those who discontin­ued NFP use for some reason. NFP studies rarely look at shifting of NFP use intention, although one in every two or three women change status over a 12-24 year period of NFP usage.

In analyzing NFP practice among the 681 women studied, we found that as a group they used their NFP methods successfully for 7,751 months out of a potential of 10,924 months of use – representing 70.95 percent. Percentages ranged from 87.83 in Ecuador to 55.48 percent in El Salvador. Mean months of use were as follows:

  • Brazil: 12.696
  • Dominican Republic: 12.236
  • Ecuador: 13.819
  • El Salvador: 8.976
  • At the end of 12 months of successful autonomous NFP use, continua­tion rates were:
  • Brazil: 79.56
  • Dominican Republic: 70.71
  • Ecuador: 83.81
  • El Salvador: 46.27

Except for El Salvador, these continuation rates are comparable to those in Mauritius after one year of NFP use: 73.5 percent for women spacing pregnancies, and 89.8 percent for women limiting pregnancies. These continuation rates are better than found in other NFP studies and show that NFP users can practice their method successfully for one year. Continuation rates appear far better for modern NFP methods than for calendar rhythm, condoms, and some other family planning methods.

More importantly, women who survive the first year of NFP use, have an even higher continuation rate in the second year. For each program country studied, it was as follows:

  • Brazil: 97.92
  • Dominican Republic: 89.41
  • Ecuador: 95.12
  • El Salvador: 93.06

There were very few drop-outs in the second year, even in the El Salvador program. This finding proves that women who survive one year of NFP use go on to successfully use it for 18 or more months. In fact, only 23 women discontinued using NFP after one year in our study.

The highest rate of discontinuation occurs in the first six months of autonomous NFP use: 56.08 percent of all discontinuations occur in this period. The study identified 174 of the 681 (25.55%) women as a hard core group of discontinuers. They used a modern method of NFP for only 4.81 months after achieving autonomy. Most (119) of these women were found in the El Salvador NFP program. Discontinuations may be higher in that NFP program because of the shorter 3-month learning period compared to learning periods of 5-12 months for the other NFP programs in the study. A large part of El Salvador’s drop-outs would have been eliminated if the learning period had been extended. We feel women who dropped out became autonomous too quickly. This can be verified by the large number who did not know how to use charts or simply disregarded charting in that program.

Most women who discontinued using a modern NFP method did so to either switch to another family planning method or used no method and were unprotected from another pregnancy. This group represent­ed 38.82 percent of the discontinuers. Of this group, only 50 women switched to other family methods, about 7.34 percent of the 681 women studied, and most opted for pills (13), or were steril­ized (11). Some returned to traditional methods such as calendar rhythm and coitus interruptus (10 women). In other words, many more women switched from other family planning methods to modern NFP methods than from modern NFP to other family planning methods. However, there is cause for concern with regard to the larger group of discontinuers who are unprotected from another pregnancy: they made up 25.99 percent of the study group of 681 women. This becomes a high risk group, mainly in El Salvador where it accounts for 42.35 percent of all Salvadorans studied.

Most women who switched to other family planning methods or who discontinued and used no other methods did so because of an unplanned pregnancy, problems of identifying the fertile signs, difficulty using charts, and lastly because they wanted a pregnan­cy. Of the 31 women who discontinued NFP use in Ecuador, 19 (61.29%) did so because they wanted a pregnancy.

There were 92 unplanned pregnancies among the 681 women studied – which represents 13.51 percent of the study group. Pearl Index Rates for 3 of the 4 NFP programs were good, the exception being the El Salvador program. The following Pearl Index Rates were calculat­ed:

  • Brazil: 8.877
  • Dominican Republic: 8.406
  • Ecuador: 4.135
  • El Salvador: 30.406

     Total study 14.234

A Pearl Rate Index of under 10 was considered good. Except for El Salvador, the Pearl Rates are comparable to those of Mauritius and most NFP programs considered to have successful NFP users. In fact, Ecuador’s Pearl Index Rate is among the best of any NFP study. The Pearl Index Rate for El Salvador is very high and is considered unacceptable. However, Medina’s Colombia study (1980) had a higher Pearl Index Rate – 37.2. When 41 very high-risk women in the study are eliminated, Pearl Index Rates for all programs improve, and for El Salvador it improves to a very acceptable 8.568. A total of 28 very high risk women were eliminated from the El Salvador Program to decrease its Pearl Index Rate. High risk-takers were those who took risks during the fertile period and did not chart daily. For Ecuador, the Pearl Index Rate fell to 2.500 and compares with any artificial method but steril­ization. Very high risk women also had unplanned pregnancies.

KM Life Tables were also calculated and were quite acceptable, usually in the 12.00-13.80 range, except for the El Salvador program (9.083).

Unfortunately, only 18 adolescents could be identified among the 681 women NFP users. The four NFP programs studied did not recruit adolescents, contrary to what they had believed. In fact, an overall review of NFP programs in Latin America showed that they do not focus on adolescents, except with fertility awareness educa­tion, which incorporates NFP, but NFP is not practiced. For the Brazil NFP program, 4.97 percent of the study group were adoles­cents. Percentages were far lower for the other study groups, and for the Dominican Republic, there were no adolescent NFP users. The small group of adolescents studied had a Pearl Index Rate of 16.107, which is higher than the Pearl Rate for all 681 women (PR=14.234). A KM Life Table calculation provided a survival rate of 13.857 months for this group, and for those using charts daily and not taking risks, the KM survival rate rose to 19 months. Most adolescents who discontinued NFP method use did not adopt another family planning method and were unprotected at the time of the study. We hope our findings on adolescents will help NFP programs in the study to focus more on adolescents. The NFP program in the Dominican Republic has already expressed a desire to do so.

The study’s finding with regard to autonomous NFP users whose partners migrated needs to be further researched. We found that this group practiced NFP autonomously for a mean of 10.07 months, but that the failure rate among the users was high, varying from a Pearl Index Rate of 31.58 for El Salvador to a low of 17.48 for the Dominican Republic. Eight (8) of the 92 unplanned pregnancies in the study fell within this group. Our data did not find any variables to explain why this group had more failures. Perhaps it is due to uncertainties about the future or psychological factors that encourage procreation before migrating.

Only 11.45 percent (N=78) of the study group switched from a modern NFP method to other family planning practices. However, when 28 women who were using lactational amenorrhoea are subtracted, the number falls to 50 women or 7.34 percent. Most women switching to other methods of family planning opted for oral contraceptives (N=13) or 1.91 percent, and sterilization (N=11) or 1.62 percent of the study group (N=681). Few women switched to IUDs and injec­tions. The highest percentages of switchers were in the Dominican Republic, 9.28 percent of the study group (N=140), and El Salvador, 8.24 percent of 255 women switched. Abstinence and charting problems, and problems identifying the fertile signs were the main reasons women switched to other methods.

The study found that 13.51 percent of the NFP users mixed NFP with other family planning methods, mainly with condoms during the fertile phase of the menstrual cycle. In other words, they mixed methods in the hope of having added protection from an unwanted pregnancy or because they wanted intercourse on fertile days. The highest numbers of women mixing methods were in Brazil (23.76%) and the Dominican Republic (19.29%). The lowest percentages were was in El Salvador (4.77%), and Ecuador (9.52%). Interestingly most mixers (67.39%) had experience with other family planning methods prior to becoming NFP users. The Pearl Index Rate for mixers was 12.68, slightly lower than that for non-mixers, 14.51. However, by individual NFP program, all Pearl Index Rates for mixers were higher, except for the Dominican Republic, where the Pearl Index Rate was 4.290 compared with 9.25 for the country’s non-mixer group. On the other hand, as an example, Brazil’s Pearl Index Rate rose from 8.877 for all Brazilian women studied to 14.230 for Brazilian mixers. With the exception of the Dominican Republic, mixers fared less well, contrary to what one would have expected with the added protection. This finding argues against the current trend of some unorthodox NFP service programs to promote condom use at the fertile phase of the menstrual cycle.

In using modern natural family planning methods, couples must abstain from sexual intercourse during the fertile time of the menstrual cycle to avoid a pregnancy. The study examined absti­nence practices and found that 21.59 percent of the women studied experienced problems with abstinence. The percentages ranged from 14.29 in Ecuador to 25.49 in El Salvador. The WHO Multi-Center Study of the Ovulation Method reported in 1987 that 16.2 percent of the women had occasional difficulties.

In the current IPHD study, 63.35 percent of the women who experi­enced problems with abstinence said that their partners demanded sex during the fertile time. Only 14.91 percent attributed abstinence problems to work. Over one in three women (37.27%) with abstinence problems discontinued using their NFP method, usually in the first year of autonomous use. Only 28.33 percent of these women switched to other forms of contraception, usually to orals and condoms.

The study found that only 44.93 percent of all modern NFP users chart their fertility signs daily. The lowest percentage was in El Salvador (26.27%). In fact, if El Salvador is eliminated, 56.10 percent of the women studied charted daily. Another 14.69 percent charted frequently. Only 32.01 percent reported never charting, and of this number, 73.39 percent were accounted for in the El Salvador NFP service program. Only 13.62 percent of the women in the other NFP programs never charted. Since charting is considered a cornerstone of modern NFP use-effectiveness, the study analyzed this variable in depth. Women who never charted ran a high risk of having an unwanted pregnancy. For example, of the 5 women who had unplanned pregnancies in Ecuador’s NFP program, 4 of them never charted.

Risk-taking was also analyzed. The study found that 69.02 percent of the women (N=681) never took risks during the fertile time to have intercourse. Again, if the El Salvador NFP group is eliminat­ed, the range for the other programs is between 87.62 percent for Ecuador to 72.93 percent for Brazil. In El Salvador, 55.29 percent of the group studied never took risks. Only 12.04 of the 681 women studied frequently took risks. For El Salvador, it was 26.67 percent, while for the other 3 countries, it was under 7 percent and for Brazil and Ecuador, under 2 percent. Also, one in three women taking risks frequently had an unplanned pregnancy. These were also generally women who expressed problems with periodic abstinence. They are also younger women than the average NFP user, have fewer children, and are better educated. There is very little switching to other family planning methods among risk-takers.

The study correlated unplanned pregnancies against categories of NFP teachers, and found that contrary to belief among NFP adminis­trators, individual teachers were more effective than teacher couples. Physicians were the least effective NFP teachers.

In conclusion, modern natural family planning methods can be very effective in avoiding an unwanted pregnancy if women users chart daily or almost daily, and take no or few risks to have sexual intercourse during the fertile period of their menstrual cycle. It also appears that learning periods of 5-12 months (prior to autonomy) are more effective than 3-month learning periods. This short learning phase is the chief reason why so many Salvadoran women became pregnant and/or discontinued using a modern natural family planning method.