Regardless of whether a woman's menstrual cycle has returned after giving birth or not, use of NFP methods during breastfeeding can be difficult. Breastfeeding not only affects the regularity of cycles (both the length and phases of the cycle) but also the common natural indicators of fertility such as cervical mucus and basal body temperature patterns. The time in which breastfeeding women often achieve pregnancy is during the transition from breastfeeding/ no cycles to breastfeeding/ cycles. Current NFP methods (both temperature and mucus based methods) manage breastfeeding while not in cycles by having women users determine a consistent pattern of cervical mucus characteristics or of dryness. Any change from the consistent pattern and three full days after is considered fertile. However, the use of either the Sympto-Thermal methods (STM) or the Ovulation Method (OM) during breastfeeding can be difficult at times. Use of current methods of NFP (during breastfeeding) results in over estimating the actual days of fertility, prolonged periods of mucus requiring long periods of abstinence, confusing mucus patterns and an increased pregnancy rate.(1-3)
Researchers at the Georgetown University Institute for Reproductive Health (IRH) have developed two simple methods of NFP, the Standard Day Method (SDM) and the TwoDay Method (TDM). Both of these methods have been reported in the literature and in past issues of Current Medical Research.(4-6) The SDM is a fixed day system in which days 8-19 of the menstrual cycle are considered fertile. The method is intended for women who have cycles between 26 and 32 days in length. When used correctly the SDM has a one-year effectiveness rate (to avoid pregnancy) close to 95%. The TDM requires the user to determine if she has observed mucus symptoms that day or the day before, if "yes" to either of those days, she then considers herself fertile. Georgetown University IRH researchers recently determined the potential (i.e., theoretical) effectiveness of both of these simple NFP methods by applying their algorithms to data charts from apast study on the effectiveness of STM with breastfeeding women.(1)(7)
The pre-existing data charts were from 73 breastfeeding women in Australia, Britain and Canada who were followed from postpartum day 42 through two potentially fertile cycles in 1986 through 1990.(1) Daily urine samples were collected and assayed for metabolites of estrogen and pregnanediol glucuronide in order to estimate the potential fertile days and the day of ovulation. The women participants also recorded the frequency of breastfeeding episodes. The Georgetown researchers utilized 274 of the potential 359 cycles in which the woman participant was fully or partially breastfeeding. Cycle zero was defined as the time before the first postpartum menses. The fertile phase was defined as the estimated day of ovulation (EW) and the five days before. The mean number of days before the first menses (i.e., for cycle zero) was 215.9 (range 65~69). The mean length of the first cycle postpartum was 34.6 days (range 15-115). By the 5th cycle the mean length was 28.6 days and the range 22-35 days.
The SDM algorithm could not be utilized for cycle zero (i.e., the time before the first menses) since it is based on counting from the first day of menses. However, when applied to the first cycle postpartum the day specific probability of pregnancy ranged from 0.0092 on ovulation day minus five to a high of 0.0753 the day before the EDO. The highest average probability of all 204 cycles was 0.0529 on the day before the EDO. The researchers concluded that SDM was not as effective for breastfeeding women as for non-breastfeeding women. The highest probability of pregnancy for non-breastfeeding women on any given day was 0.0108 in past studies. However, when they applied the algorithm to just those cycles that fell within the 26-32 day cycle length range, the highest probability was 0.0170 (N = 111 cycles) on the day before the EDO. They also found that by waiting 4 or more cycles after menses resumes, the highest probability was 0.0338 the day before the EDO. The researchers calculated that up to 75% of breastfeeding women would not be able to use the SDM in the early postpartum period.
Unlike the SDM, the TDM could theoretically be used during cycle zero when the women participants were not in cycles. This is so since the TDM is based upon the presence or absence of cervical mucus and not the first day of menses. However, the Georgetown researcher found that during cycle zero, there was a mean of 77 days with detected secretions and during the later part of cycle zero (i.e., as the women participants approached their first ovulation) 80% or more of the days had cervical secretions. They concluded that based on the extensive number of days of secretions and the extensive time required for avoiding intercourse, the TDM may not be acceptable for breastfeeding women not in cycles.
However, when the TDM was applied to breastfeeding women who were in cycles it was theoretically very effective. The highest day specific probability of pregnancy for all cycles (N = 204) was 0.009 on ovulation day minus 4. The probabilities of pregnancy ranged from a high of 0.0142 two days before the EDO in the first cycle after the return of menses to 0.0026 on the EDO and the EDO minus day 3 and day 5. The researchers also found that the probability of pregnancy was very low regardless of the daily number of breastfeeding episodes. However, they did notice that those women who breastfeed 6 or more times a day experienced less cervical secretions.
A final issue that the researchers addressed when using the SDM and the TDM during breastfeeding was the length of abstinence required. Obviously the SDM requires only 12 days on a consistent basis when used by breastfeeding women who are in cycles. The TDM required a mean of 18.7 days (median 19) and a range of 3-84 days. The number of days as a proportion of the cycle calculated out to be a mean of 52.9% - which is about half of the length of the menstrual cycles included in the study. In comparison, the study in which the pre-existing data was obtained determined that a mean of 79% of the days would be required for abstinence with the Sympto-Thermal method (STM).(1)
Another interesting finding from the Georgetown research was that 67% of the women participants ovulated before their menses. However, the researchers calculated that only 49% of these cycles could sustain a pregnancy based on the estimated day of ovulation and the length of the luteal phase. Women who breastfeed less than 5 times a day were more likely to have an ovulatory cycle zero that could sustain a pregnancy.
Although the SDM and the TDM theoretically have an effective application for specific sub-groups of women during breastfeeding (e.g., the SDM once regularity is assumed and the TDM for the early breastfeeding in cycles time period) the researchers concluded that there remains a need for simple fertility awareness based methods during breastfeeding. The Georgetown researchers suggested further research and "tweaking" of these simple natural methods, such as extending the SDM from 12 days to a longer time period during the first cycles after the first menses (i.e., until cycle regularity is established) and possibly combining the SDM and TDM.
Teachers and advocates of the STM and OM methods might argue that their methods are already simple and effective during breastfeeding. However, the length of abstinence required and the actual effectiveness to avoid pregnancy (e.g., around 78%) invites us to find better ways. I am pleased that the Georgetown IRH research group has ongoing research to help get a better understanding of natural methods during breastfeeding and their effectiveness.(RJF)
1. Labbok, MX., Stallings, R.Y., Shah, F., Perez, A., Klaus, H., Jacobson, M., and Muruth, T. Ovulation method use during breastieeding: Is there increased risk of unplanned pregnancy? American Journal of Obstetrrcs and Gynecology. 1991 ;165:2031-2036.
2. Zinaman, M. and Stevenson, W. Efficacy of the sympto-thermal method of natural family planning in lactating women after the return of menses. American Journal of Obstetrics and Gynecolow. 1991;165:2037-2039.
3. Kennedy, K.I., Gross, B.A., Parnteau-Carreau, S., Flynn, A.M., Brown, J.B. and Visness, C.M. Breastfeeding and the sympto-thermal method. Studies in Family Planning. 1995;26:107-115.
4. Arevalo, M., Jennings, V. and Sinai I. Efficacy of a new method of family planning: the Standard Day Method. Contraception. 2002;65: 333-338.
5. Sinai, I., Jennings, V. and Arevalo, M. The TwoDay Algorithm: A new algorithm to identify the fertile time of the menstrual cycle. Contraception. 1999;60:6~70.
6. Jennings, V. and Sinai, I. Further analysis of the theoretical effectiveness of the TwoDay method of family planning. Contraception. 2001;64:149-153.
7. Arevalo, M., Jennings, V. and Sinai I. Application of simple fertility awareness-based methods of family planning to breastfeeding women. Fertility and Sterility. 2003;80:1241-1248.