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The Spacing of Babies with Ecological Breastfeeding (1989)

Sheila K. and John F. Kippley

Our personal interest in the baby-spacing effects of breastfeeding dates back to 1967-1969. We moved to Canada in the summer of 1967, and Sheila proceeded to establish the first chapter of La Leche League International in the Province of Saskatchewan. The standard first meeting of LLL's regular course of instruction reviews the advantages of breastfeeding, and the natural spacing of babies is listed as one of the advantages. Sheila began to get a number of questions about this, reviewed the research, concluded that frequent suckling was a key ingredient, and wrote Breastfeeding and Natural Child Spacing which we published in 1969. It was at that time that we coined the phrase "ecological breastfeeding" to distinguish it from "cultural breastfeeding." The former spaces babies, the latter does not. However, since most people are acquainted with only the latter, claims of extended postpartum infertility, while breastfeeding, tend to be scoffed at.

Recognizing the need for new data that applied to North American women, we included a survey in the book, and Sheila first reported the results at the La Leche League International Convention in 1971; they were then published in John Harrington's newsletter1 and in a nursing journal.2

The 1971 study reported on 112 nursing experiences of 72 mothers; most of those experiences had occurred before reading Breastfeeding and Natural Child Spacing. In these 112 experiences, the mothers averaged 10.2 months of breastfeeding amenorrhea. Then we selected six criteria for ecological breastfeeding (they are given below), and we found that 29 of the 112 nursing experiences fulfilled the requirements for ecological breastfeeding. In these 29 experiences, the mothers nursed for an average of 22.8 months, 40% longer than the 16.3 months of nursing for the entire sample. Most significantly, the ecologically breastfeeding group averaged 14.6 months of breastfeeding amenorrhea, and this was 43% longer than the average of 10.2 months experienced in the entire sample of 112 nursing experiences. In this study, the entire sample of 112 always included the 29 ecological breastfeeding experiences, and this raised the average nursing duration and amenorrhea of the entire sample.

After our initial publication, other studies showed both longer and shorter durations of breastfeeding amenorrhea. Monique Bonte found that 75% of rural breastfeeding women in Rwanda conceived between 24 and 29 months postpartum; however, among their city cousins who were developing nursing patterns closer to Western cultural nursing, 75% were conceiving between 6 and 15 months postpartum.3 An even more dramatic example of frequent nursing and extended amenorrhea was reported by Konnor and Worthman; observing the !Kung tribe, they found that the babies were nursing an average of two minutes every fifteen minutes, and the mothers were conceiving at about 35 months.4 A shorter average of 9 months (41 weeks) of amenorrhea among Australian mothers was reported by Barbara Gross.5

The average duration of amenorrhea reported by Gross (9.5 months) was very close to the average we reported in 1971 (10.2 months), but both were considerably shorter than the 14.6 months with full ecological breastfeeding. The results of these other studies made it desirable to check the results of our first survey.

Between 1971 and 1985, we accumulated a large number of breastfeeding surveys, and in 1985 we decided to run a second analysis to determine if it was still appropriate to state that ecological breastfeeding produces an average of 14 months of breastfeeding amenorrhea. Our first step was to print our standard breastfeeding survey in the May-June 1985 issue of The CCL News, the bi-monthly newsletter of the Couple to Couple League. A total of 286 surveys was entered into the computer.

To select the group of experiences which qualified as ecological breastfeeding, we selected the same six criteria used in the 1971 study:

  1. No pacifiers used;
  2. No bottles used;
  3. No liquids or solids used for five months;
  4. No feeding schedules other than baby's;
  5. Presence of night feedings; and
  6. The presence of lying-down nursing for naps and night feedings.

These criteria were selected because each of the above behaviors influences the frequency of suckling. A computer search of the 286 records yielded 98 nursing experiences that met all of the above criteria for ecological breastfeeding.


Duration of Breastfeeding

The 286 nursing experiences averaged 20.4 months of nursing. That was 25% longer than the average duration of 16.3 months in our 1971 study, and 32% longer than the average reported by Gross. We speculate that the increase over the 1971 duration may be due to two factors: 1) an increased social acceptance of more extended nursing and 2) the influence of reading Breastfeeding and Natural Child Spacing and the "natural mothering" columns in the newsletter of the Couple to Couple League. As mentioned previously, most of the 1971 nursing experiences were completed before such reading, while the fact that the 1986 surveys came from readers of the newsletter suggests that its regular encouragement of extended ecological breastfeeding may have had an effect.

Duration of Amenorrhea: Total Sample
The average duration of amenorrhea for the entire sample of 286 nursing experiences was 11.7 months. This is 15% longer than the average of 10.2 months found in our 1971 study and 23% longer than the 9.5 months (41 weeks) reported by Gross.

Duration of Amenorrhea: Ecological Breastfeeding
The average duration of the 98 ecological breastfeeding experiences was 14.5 months. This is almost identical to the 14.6 months we reported in 1971; it is 24% longer than the 11.7 months of amenorrhea of the entire sample of 286 experiences.

In this study we were able to separate the ecological breastfeeding experiences from the rest of the sample and then compare the former with the latter. The results are shown in Table 1. The totals of the two groups add up to 284. (Two computer records failed to be tallied.)

Click here for Table 1.

The difference between the ecological breastfeeding experiences and the cultural nursing experiences stands out much more in this comparison than in those which compared the ecological breastfeeding experiences to the entire sample which also included them. By separating them, we see that those mothers doing ecological breastfeeding nursed for an average of 25.7 months, 46% longer than those doing a more cultural form of breastfeeding. In turn, their average duration of 14.5 months of amenorrhea was 41% longer than the average of 10.3 months for the cultural breastfeeding experiences.

We then tried to discover if there was any single one of the six criteria of ecological breastfeeding that, by itself, showed an even greater duration of amenorrhea, but we found none.

We tested a different criterion, total breastfeeding for the first 6 months (as contrasted with the criterion of 5 months used in the ecological breastfeeding criteria). In 79 experiences, the baby took no other nourishment for the first six months, and the mothers averaged 14.8 months of amenorrhea. However, total breastfeeding usually lasts for only 5 to 7 months unless the baby is experiencing allergies, so the total breastfeeding for six months by this sub-sample could not account for the continuation of amenorrhea for an average of another 8 months. Rather, the total breastfeeding for 6 months or a bit more perhaps indicated a combination of the baby's suckling needs and the mother's attitude towards baby-led introduction of other foods, and this pattern may have carried forward for many months.

Range of Amenorrhea: Ecological Breastfeeding
While the average amenorrhea among the 98 ecological breastfeeding experiences was 14.5 months, the range was considerable as seen from Table 2. Of special concern are those with a very early return of menses. Table 2 shows seven experiences with less than 7 months of amenorrhea; of those 7, one was 1 month, two were 2 months, one was 3 months, and three were 5 months. Of the 36 experiences between 7 and 12 months of amenorrhea, the distribution was fairly even; four were 7 months; five were 8 months; six were 9 months; four were 10 months; eight were 11 months; and nine were 12 months. At the other end of the range, three had 26 months, three had 27 months, one had 28 months, and one had 30 months of amenorrhea.

In this sample, 44% of the nursing experiences had 12 months or less of amenorrhea. On the other hand, the remaining 56% had more than a year of breastfeeding amenorrhea. Furthermore, there is a 1/3 probability (34%), according to this sample, that the mother who continues with ecological breastfeeding will have 18 months or more of amenorrhea. That is not self-evident from Table 2; it includes ten experiences of 18 months plus the 23 experiences of 19 to 30 months.

Click here for Table 2.


Postpartum Infertility
The results of our two surveys lend credence to the theory that the principal factor in determining the length of breastfeeding amenorrhea is the frequency of suckling. It was once commonly held that breastfeeding generally spaces babies about two years apart, but experiences with cultural breastfeeding led many to regard such talk as an old wives' tale. Now we have the basis for stating that, in fact, such spacing does occur among modern North American women leading normal lives.

It is noteworthy that the average duration of amenorrhea among those experiences classified as "cultural breastfeeding" (10.3 months) is slightly longer than the entire sample reported by Gross (9.5 months) and considerably longer than others. For example, Pascal reported an average of only 58 days of amenorrhea among 449 nursing mothers.6 More recently, Diaz at al. reported that among a group of urban Chilean women, only 49% of fully breastfeeding mothers were still amenorrheic at the end of six months postpartum.7 In our survey, 73% of the culturally nursing mothers were still amenorrheic at the end of six months. We speculate that many of those experiences which we classified as cultural breastfeeding were still close enough to ecological breastfeeding to account for the significantly longer amenorrhea experienced in our study compared to the others cited.

Our studies show that it is essential to differentiate between ecological and cultural breastfeeding. By way of comparison with data cited in the previous paragraph, 93% of the mothers doing ecological breastfeeding in our 1986 study were still amenorrheic at the end of 6 months. It is an old wives' tale that cultural breastfeeding will space babies; it is proven that ecological breastfeeding will provide an average of 14.5 months of breastfeeding amenorrhea.

We recognize that the first postpartum period is not the best marker of the return of fertility. Gross5 cites various authors to indicate that ovulation occurs before the first period from 23 to 33% of the time (pp.111, 119), but actual pregnancies occurring before the first period are in the range of 5 and 6% when the couple practice random intercourse and no method of birth control.8 Furthermore, some women remain infertile for one or two cycles after their first menses. Therefore, we think it is incontrovertible to state that ecological breastfeeding spaces babies an average of two years apart without any conscious effort at family planning.

In our study, we limited ourselves to an analysis of variables that can affect the duration of postpartum amenorrhea. We did not analyze pregnancies. However, those who are concerned about detecting the return of fertility before the first postpartum period can take comfort from the results reported by Gross5 about women who chiefly relied on mucus-only before the first period: "No pregnancies occurred before the first menstrual bleed while breastfeeding or after weaning" (p. 117). She also noted that Perez found a method unplanned pregnancy rate of 4.6% before the first period and another 4.5% after the first period (p.120).

The Range of Postpartum Amenorrhea
The question remains: Why is there such a range of amenorrhea among women who are apparently practicing the same form of baby care with frequent nursing, that is, ecological breastfeeding? Our survey may not have been a sufficiently accurate instrument to detect important differences in nursing patterns, but its results corroborate the experience we have had on an ongoing basis through personal counseling.

A more sensitive instrument was used by William Taylor in his study of breastfeeding amenorrhea, and he was able to distinguish the precise frequency and duration of nursing in each 24-hour period. Summarizing his findings, Dr. Taylor stated: "These results suggest that the amount of suckling, especially if occurring in short, frequent bouts, provides the key stimulus necessary to delay the return of ovulation after childbirth."9 Incidentally, the hypothesis that the duration of breastfeeding amenorrhea is significantly affected by the mother's nutrition and weight-to-height ratio has been pretty well discounted, according to Taylor9 (pp.23-27).

In exploring the possibility of predicting the duration of amenorrhea for any given woman, Taylor constructed an interesting probability scale based on frequency and total duration (p. 99), but even with Taylor's closer analysis, we are not yet to the point where we can guarantee to any individual woman that if she follows such and such a breastfeeding pattern, she will remain infertile for "X" number of months or for the next 30 days. Based on anecdotal experience, we think that fatigue and stress contribute to an early return of fertility, but such variables are highly subjective and are not easily subject to scientific study. A certain range seems to be a matter of individual differences.

Implication for the NFP Movement

Making the Distinction
We think it is self-evident that all teachers of natural family planning should clearly distinguish between ecological breastfeeding and cultural breastfeeding.

The same issue of the International Review of Natural Family Planning which carried the article by Barbara Gross also included an interchange between Malcolm Potts and Father John Harvey. Potts questioned whether "not to employ this method [breastfeeding] is wrong and therefore sinful, unless it proves gravely inconvenient or is physically impossible."10 Considering the involvement of Dr. Potts in the promotion of contraception and abortion, the sincerity of his question is questionable, but he raised a good point. Reviewing the five major benefits Potts had argued for breastfeeding, Fr. Harvey replied: "If these benefits of breastfeeding can be further substantiated, then it would seem that it is time to formulate a strong moral argument in favor of breastfeeding."11 John Kippley replied in the next issue of the IRNFP that "further research, while perhaps helpful for additional confirmation, is really not needed. The aforementioned benefits are so well established that the time has already come for that strong moral argument."12

The basic primer for the scientifically established health advantages of breastfeeding remains a collection of seven symposium papers edited by the Doctors Jelliffe and Jelliffe.13 There is no question that ecological breastfeeding spaces babies and that it provides the best nourishment for the baby as well. We think that stressing a moral obligation to breastfeed may be counterproductive, but we think that every natural family planning program should be in the forefront of advocating ecological breastfeeding-first because it is best for baby and secondly because it is the Creator's original plan for spacing babies.

Providing Support
In advocating ecological breastfeeding, it is important to remember that this form of baby care is countercultural. It is culturally acceptable to do "total breastfeeding" (nothing except mother's milk) for the first few weeks, but soon the breastfeeding mother will feel the pressure to use pacifiers, to try to get her baby to sleep all the way through the night, to leave her baby for short and then increasing intervals, all of this while still doing "total breastfeeding." And, of course, that helps to illustrate the great difference between "total breastfeeding" and ecological breastfeeding. Then she will feel the cultural pressures to start using a supplemental bottle or to introduce solids earlier than 5 to 7 months. (Of course, if the mother is driven by economic necessity or capitulates to convenience or social pressures to work outside the home, she will not be able to practice ecological breastfeeding except in those rare cases where she can have her baby right with her and nurse ad libitum.)

To overcome both the conscious and subconscious pressures to depart from ecological breastfeeding, a mother needs support from her husband, a friend who has done it, and something to read. To provide the latter support, an enlarged and revised edition of Breastfeeding and Natural Child Spacing: How Ecological Breastfeeding Spaces Babies is now republished in early 1989.14 Written in a colloquial, non-scientific style, it shows mothers practical ways to overcome the cultural obstacles they will meet.


  1. Kippley, John F. and Sheila K. "Report on a Survey on Breastfeeding and Amenorrhea." Marriage and Family Newsletter 3:3 (March 1972): 1-7.
  2. Kippley, Sheila K. and John F. "The Relation between Breastfeeding and Amenorrhea: Report of a Survey." Journal of Gynecological and Neonatal Nursing 1:4 (November- December 1972): 15-21.
  3. Bonte, Monique, et al. "Influence of the socio-economic level on the conception rate during lactation." International Journal of Fertility (1974): 97-102.
  4. Konnor, Melvin and Worthman, Carol. "Nursing frequency, gonadal function, and birth spacing among !Kung hunter-gatherers." Science 207 (February 15, 1980): 788-791.
  5. Gross, Barbara A. "Breastfeeding and the Return to Fertility." International Review of Natural Family Planning VIII:2 (Summer 1984): 102-120.
  6. Pascal, Juliette. “Some Aspects of Postpartum Physiology” (Doctoral thesis presented at the University of Nancy, France, October 1969); translation and summary by Dr. Suzanne Parenteau-Carreau and Dr. Claude Lanctot.
  7. Diaz, S., et al. “Breastfeeding pattern and the duration of lactational amenorrhea, anovulation and infertility in urban Chilean women.” Contraception (in press); quoted in Research in Human Reproduction: Biennial Report (1986-1987), ed. by E. Diczfalusy et al. (Geneva: WHO, 1988): 251.
  8. Five percent among Quebec mothers: Remfry, Leonard. “The Effects of Lactation on Menstruation and Pregnation,” Transactions of the Obstetrical Society of London 38 (1897): 22-27; 5:4% in Rwanda: Bonte, Monique, and van Balem, H. “Prolonged Lactation and Family Spacing in Rwanda.” Journal of Biosocial Science 1:2 (April 1969): 97-100; 6% among American mothers: Prem, Konald A. “Postpartum Ovulation.” (Unpublished paper delivered at La Leche League International Convention, Chicago, 1971.)
  9. Taylor, Harry William, Jr. “Effect of Nursing Pattern on Postpartum Anovulatory Interval.” (University of California, Davis: Dissertation in Biomedical Engineering, 1989): 130.
  10. Potts, Malcolm. “Letters,” International Review of Natural Family Planning VIII:2 (Summer 1984): 174-178.
  11. Harvey, John F. “Letters.” International Review of Natural Family Planning VIII:2 (Summer 1984): 178-180.
  12. Kippley, John F. “Letters.” International Review of Natural Family Planning VIII:3 (Fall 1984): 27.
  13. Jelliffe, D.D., and Jelliffe, E.F.P., eds. “The Uniqueness of Human Milk.” Originally published in The American Journal of Clinical Nutrition 24 (August 1971): 968-1024.
  14. Kippley, Sheila K. Breastfeeding and Natural Child Spacing: How Ecological Breastfeeding Spaces Babies. Cincinnati, Ohio: The Couple to Couple League, 1989.

Previously published in International Review of Natural Family Planning, Spring/Summer 1989.