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The Relation Between Breastfeeding and Amenorrhea:
Report of a Survey (1972)

Sheila Kippley, BS, and John F. Kippley, MA, MAT

Nursing mothers completed questionnaires concerning various breastfeeding practices. First, those questionnaires lacking sufficient data were eliminated; then two more samplings were made, one of mothers who fed exclusively by breast for at least 5 months and the other of mothers who met the criteria for complete "natural mothering." Each sample was analyzed according to duration of breastfeeding and duration of amenorrhea, and the findings were compared. The all-inclusive sample averaged 10.2 months of amenorrhea; the sample of mothers who fed exclusively by breast, 11.6 months; the natural mothering sample, 14.6 months. The authors compared their results with those of other studies and concluded that breastfeeding, lactation amenorrhea and the resulting extended postpartum infertility comprise a delicate symbiotic relationship involving the ecologic interdependence of the mother and child. (An extension of the conclusion is offered: the right of nursing mothers to know how certain cultural practices can upset such an ecology.)

In several studies of the relation between breastfeeding and the infertility it induces, the observation has been made that supplementary feedings reduce infertility.1-3 Other studies4-6 have revealed a vast difference between the breastfeeding-amenorrhea experience of Asian-Indian women and women of the North American-European culture. Peters, Israel and Purshottam5 showed that lactation amenorrhea of a year was quite common among Indian women, while Pascal7 studied a French group whose lactation amenorrhea averaged only 58 days. Salber, Feinleib and Macmahon8 showed that in more than 60% of mothers who nursed for 6 months menses returned by 6 months. Gioiosa's analysis9 of a La Leche League survey indicated that the early introduction of formulas and other foods reduced infertility in lactating mothers even in the early months.

Various studies have pointed to the role of the sucking stimulus in relation to lactation amenorrhea, and it has become apparent to us that the sucking stimulus is the main factor behind lactation amenorrhea.10-15 We discovered that suckling is related to "natural mothering," i.e., the absence of bottles, pacifier, etc., with the mother meeting the baby's various physical and emotional needs via the breast. Natural mothering seems to provide the sucking stimulation at the breast necessary for inhibiting ovarian and menstrual activity.

A questionnaire was designed to investigate a number of variables that can influence the amount of sucking by the baby. The purpose of the study was a) to compare amenorrhea on the basis of different types of baby care and b) to test the following hypothesis: Mothers who breastfeed according to a system of total natural mothering will experience a period of amenorrhea which will be significantly longer than that experienced by those who breastfeed in accord with certain cultural practices (use of bottles, pacifiers, early solids, etc.).

Methods
Starting in June 1970 the questionnaire on breastfeeding experience was included in each copy of Breastfeeding and Natural Child Spacing by Sheila Kippley,16 and reader-mothers were requested to complete and return it (see Figure 1). Name and address were not requested. By June 1971 questionnaires representing 142 nursing experiences had been returned from 77 mothers. Because of insufficient data, 30 returns were eliminated. The resultant sample consisted of 112 nursing experiences, of at least 4 months' duration, from 72 mothers, and most of these experiences occurred prior to reading Breastfeeding and Natural Child Spacing.

These questionnaires were further examined to select a) those mothers who breastfed exclusively for at least 5 months and b) those mothers who followed the approach to mothering and infant care recommended in the book mentioned above.

Length of amenorrhea was taken from the response to, "How old was your baby when your periods returned?" For the statistical analysis, a response of anywhere from 1.0 to 1.9 was recorded as 1.0, thus yielding a slightly conservative bias. In those cases where amenorrhea was reestablished, we recorded amenorrhea only in terms of the first menstrual bleeding.

Results

Entire Sample
The 112 nursing experiences ranged from 4 to 37 months of breastfeeding. (Data were not complete since some mothers stated that they were still nursing.) Table 1 indicates the distribution of this sample by months of breastfeeding; Table 2, the distribution by months of amenorrhea. This group experienced an almost equally wide range of amenorrhea-from 1 to 30 months.

Click here for chart.

Total Breastfeeding Sample
The range of 1 to 30 months of amenorrhea among women who were all interested enough to breastfeed from at least 4 months to more than 3 years led us to look for factors that might be significant in accounting for the difference in amenorrhea experience. Thus, we selected first of all only those cases where the mother gave no solids or liquids until the baby was at least 5 months old. This "total breastfeeding" group offered only mother's milk for their baby's nourishment. No juices, formula, water or cereals and other solids were given during the total breastfeeding period. This selection yielded 75 nursing experiences. Tables 3 and 4 give the results of statistical analysis, with Table 4 showing that while the range of amenorrhea experience duplicated that of the larger group, the mean average had lengthened to 11.6 months.

Click here for sample experience questionnaire.
Click here for Distribution Charts (tables 3 and 4).

Natural Mothering Sample
The third and perhaps most striking analysis was achieved by selecting only those cases that met our criteria for natural mothering, a term used to signify that type of baby care in which the baby had ample opportunity to suck at the breast for both physical and emotional nourishment. In addition to the criterion of mother-only nourishment in the early months that characterized the selection of the previous group, the criteria for this group included the exclusion of such items as pacifiers and the inclusion of certain nursing practices such as lying-down nursing. These criteria were directly related to practices that increase or decrease the sucking of the baby at the breast:

  • No pacifiers used
  • No bottles used
  • No solids or liquids for 5 months
  • No feeding schedules other than baby's
  • Presence of night-feedings
  • Presence of lying-down nursing (naps, night-feedings)

Tables 5 and 6 illustrate the results of analysis of this sample. These cases ranged from 12 to 37 months of breastfeeding (not complete, as some mothers were still nursing at date of questionnaire); the mean was 22.8 months. This group experiences a significant increase in the duration of amenorrhea, with a mean of 14.6 months-an increased of 43% over the mean of the entire sample of 112. The range of 1 to 30 months of amenorrhea duplicated that of the entire questionnaire sample. Comment The significance of these results comes from a comparison with other studies. Pascal's7 3-year study of 449 French (Parisian) nursing experiences (1965-1968) dealt with a group of women who did not nurse as long and who experienced a relatively short duration of amenorrhea. In the Pascal study, only 7% of the babies were breastfed for 6 months or more; in the present study, 98% of the babies were breastfed for 6 months or more. Pascal's group averaged only 58 days of amenorrhea, while in the present study

Click here for Distribution Charts (tables 5 and 6).

an average of amenorrhea of 10 months was found. On the other hand, the present study shows that American women can have a breastfeeding-amenorrhea experience similar to that found among Asian-Indian women.5 In other words, the difference found in previous studies has been explained in this study of a group of American women who have breastfed according to a natural, ecologic pattern. We draw the inference that the differences are due, not to biologic differences, but to cultural practices that can be transcended by an informed mother.

The present study cannot be considered a study of breastfeeding and amenorrhea experiences from a representative sample of U.S. mothers. Rather, it is a study of mothers who were rather seriously interested in breastfeeding and the natural aspects of mothering. By selecting a subgroup of mothers who engaged in a rather full pattern of satisfying the baby's nutritional and emotional sucking needs at the breast, the study has pointed out the effect of cultural conditioning on breastfeeding-amenorrhea. Those whose breastfeeding practice was quite ecologically balanced and free from the usual cultural artifacts (such as pacifiers) and practices (such as avoiding night-feedings) experienced an amenorrhea with a mean 43% greater than the sample as a whole. The sample as a whole showed an average duration of amenorrhea five times that of the sample in the Pascal study.

Special Notes Analysis of the individual questionnaires revealed some interesting data not presented in the above tables. Early Return of Menses The woman who engaged in the natural mothering program and yet experienced the return of menses at 6 weeks postpartum (1 month in the tables) volunteered the information that she kept basal temperature charts. Her obstetrician interpreted these as indicating non-fertile periods up through the 11th menses. The mother with a menses return 4 months postpartum also used basal temperature charts and indicated a return of ovulation 6 or 7 months postpartum. These were the only 2 cases of menses returning prior to 7 months postpartum in our sample of 29 cases of natural mothering. Conception Prior to Menses In the entire group of 142 returned questionnaires, there were 14 instances of pregnancy occurring prior to the return of menses. (Eighty-nine of the 142 cases indicated reliance on amenorrhea for conception regulation.) Thirteen (13) of these questionnaires provided enough detail for analysis of baby care-feeding programs. Of these, only 2 were among the 29 who followed the program of total natural mothering. One mother conceived at 27 months postpartum, but she had deliberately reduced the nursing in order to conceive; the other mother became pregnant at 15 months postpartum. The other 11 were from the larger sample whose nursing habits were more typical of the American culture. An analysis in Table 7 indicates significant factors in their nursing or mothering patterns.

Click here for Analysis Table 7.

There were no conceptions by any mother in the natural mothering group of 29 prior to the 12th month, and the earliest conception without a "warning" menses was the 15th months, as stated above.

Conclusions
The results of this study provide further support for the statement: Ecologically natural breastfeeding effectively provides natural infertility prior to menses. "Ecologically natural" refers to the pattern described as natural mothering. What is the rate of effectiveness? Our sample indicated 100% effectiveness in the first year prior to menses, but we would not claim that incidence on a larger scale. Dr. Konald Prem17 of the University of Minnesota Medical School notes that in 1895 Remfry found that the chances of pregnancy during amenorrhea were 6 in 100. Prem's own research corroborated this. On the basis of those studies plus our own, we feel warranted in saying that the mother who follows the natural mothering program of nursing her baby will have a 95% probability of remaining infertile prior to the return of menses. We think, further, that U.S. women who follow the natural mothering program will, on the average, experience 12 to 16 months of amenorrhea. Thus, those who rely only on the natural breastfeeding program for family planning can, on the average, anticipate 21 to 25 months between births. We can make these statements, in full awareness of the many pregnancies that occur during breastfeeding, because we have limited them to cover only mothers who are willing to run contrary to the customary advice of many physicians (e.g., "start cereals at two weeks") and certain cultural practices (e.g., "let the baby cry it out"). Those who are willing to take care of their baby's nutritional and emotional needs through breastfeeding should be specifically informed about the ecologic interdependence of mother and baby. Like many such relationships, this one has a certain delicacy, and nursing mothers who would appreciate the period of extended natural infertility deserve to know how a cultural practice such as using a pacifier can upset the balance and greatly reduce the chances of extended natural infertility.

References

  1. Rice, F.: "The Function of Lactation." The Family Today NCWC, 1944, pp 96-100
  2. Gioiosa, R.: "Incidence of Pregnancy during Lactation in 500 Cases." Am J Obstet Gynecol 70:162, 1955
  3. Cronin, T.J.: "The Influence of Lactation upon Ovulation." Lancet 2:422, 1968
  4. Tietze, C.: "The Effect of Breastfeeding on the Rate of Conception." International Population Conference, NY, September 1961 (unpublished)
  5. Peters, H., S. Israel and S. Purshottam: "Lactation Period in Indian Women-Duration of Amenorrhea and Vaginal and Cervical Cytology." Fertil Steril 9:134, 1958
  6. Silverberg, S.: "Selected Abstracts." Am J Obstet Gynecol 82:1196, 1961
  7. Pascal, J.: "Some Aspects of Post-Partum Physiology." (1969). Translation summary sheets available through the Natural Family Planning Association, New Haven, Connecticut
  8. Salber, E., M. Feinleib and B. Macmahon: "The Duration of Postpartum Amenorrhea," Am J Epidemiol 82:347, 1966
  9. Gioiosa, R.: "Breastfeeding and Child Spacing." Reprint #121, La Leche League, Franklin Park, Illinois
  10. Sharman, A.: "Ovulation after Pregnancy." Fertil Steril 2:371, 1951
  11. McKeown, T., and J. R. Gibson: "A Note on Menstruation and Conception During Lactation." J Obstet Gynecol Br Commonw 61:824, 1954
  12. Minaguchi, H., and J. Meites: "Effects of Suckling on Hypothalamic LH-Releasing Factor and Prolactin Inhibiting Factor, and on Pituitary LH and Prolactin." Endocrinology 80:603, 1967
  13. Udesky, I.: "Ovulation in Lactating Women." Am J Obstet Gynecol 59:843, 1950
  14. Grosvenor, C.E., F. Mena and D.A. Schaefgen: "Effect of Nonsuckling Interval and Duration of Suckling on the Suckling-Induced Fall in Pituitary Prolactin Concentration in the Rat." Endocrinology 81:449, 1967
  15. "Neuroendocrinology and Reproduction in the Human." WHO Technical Report Series No. 304, Geneva, Switzerland, World Health Organization, 1965
  16. Kippley, S.: Breastfeeding and Natural Child Spacing. Cincinnati, Ohio, K Publishers, 1969
  17. Prem, K.: "Post-Partum Ovulation." La Leche League International Convention, Chicago, 1971 (unpublished)

Previously published in Journal of The Nurses Association of The American College of Obstetrics and Gynecologists, 1:4, November-December 1972