by Kathleen M Merchant, PhD, Consultant to the International Food Policy Research Institute, Washington, D.C.
The issue addressed here is maternal nutritional depletion - the negative energy balance and/or micronutrient deficiencies resulting from the energetic burden of frequent reproductive cycling (one cycle being conception, pregnancy, lactation/postpartum) combined with undernutrition and overexertion - and its impact on a womans health and nutritional status and that of her offspring. The article is thus concerned with the impact of nutritional depletion that occurs during a womans life cycle, as opposed to the effects of nutritional depletion that occur intergenerationally.
A brief summary of the recognition and controversy regarding the effects of reproductive stress (or frequent reproductive cycling) is followed by a description of the factors that make assessment and identification of specific consequences so complex, and finally approaches are suggested to alleviate maternal nutritional depiction, including suggested policy directions and areas for research.
It has been common practice to categorize the condition of maternal nutritional depletion as a syndrome brought on by too frequent reproductive cycling. The phrase Maternal Depletion Syndrome was first popularized by Jelliffe in 1964(1) in a description of the very marginal existence of a population in Papua New Guinea where the women endured very high energetic burdens of physical labour compounded with very high energetic burdens of frequent reproductive cycling and very low consumption of nutrient-rich foods. After introduction of this term, however, controversy arose regarding the existence of such a syndrome(2), and following further investigation of the condition, it now seems clear that syndrome is not the appropriate description in this case, because the condition manifests itself through a relatively general set of symptoms, most of which are common to any form of chronic undernutrition or negative energy balance. That is, frequent reproductive cycling itself does not appear to cause a syndrome per se (with the exception of an exacerbation of a number of micronutrient deficiencies such as iron and vitamin A), but in circumstances where a population is maintaining a marginal existence based on a fragile energy balance, frequent reproductive cycling will exert a significant stress, tipping the balance for the women of this population to even greater risk of undernutrition with negative consequences for her and her offspring(3).
Maternal nutritional depletion should be a recognized condition of undernutrition particularly to women, describing the situation in which factors of deprivation (high physical burdens with chronically low food consumption) combined with the energetic burden of frequent reproductive cycling, produce negative outcomes for mother and child.
Part of the reason maternal nutritional depiction has continued to remain controversial is that early efforts to establish its existence were overly simplistic leading to inconsistent results. Investigators did not generally accurately quantify reproductive stress and womens nutritional status, instead using inadequate indicators such as parity and maternal weight. When no relationships were found they frequently concluded that frequent reproductive cycling was not a significant nutritional stress.
A simple measure of parity masks the complexity of reproductive cycling which at a minimum includes the frequency and duration of periods of gestation, as well as the frequency, duration and intensity of periods of lactation. Although highly dependent on the amount of milk produced, the energetic cost of lactation is consistently higher than that of pregnancy and generally of longer duration. And yet a measure of parity does not take into account any differences in lactation between reproductive cycles or any variation in timing between cycles. Timing between cycles can be crucial because of opportunities for nutritional recovery or recuperation.
Weight similarly is of limited use as an indicator here, for example not indicating circulating levels and stores of vitamins and minerals, clinical signs of deficiency, nor availability of body tissue stores such as fat. Moreover, during every phase of the reproductive cycle, womens weight can vary solely due to physiological changes in water balance which have no bearing on nutritional status; there is great variation in water retention between women and within a woman between reproductive cycles.
Additionally, some researchers have suggested that women adapt to the high energetic burden of reproduction and use energy more efficiently when their system is energetically stressed (4). This is proposed on the basis of surprisingly positive reproductive outcomes resulting from relatively low measured levels of intake relative to projected calculations of required intake, and relatively high levels of energy expenditure in some populations. Biologic mechanisms for this energetic adaptation have not been proposed. It seems that upon closer examination of current data available, rather than adaptation, it is more likely that our ability to accurately measure the components of energy balance in free-living populations is flawed.
Within deprived populations, when indicators of reproductive stress and nutritional status have been specified accurately, there is clear evidence of the relationship between high reproductive stress (exemplified by frequent, closely spaced reproductive cycles) and low nutritional status (exemplified by lower fat stores, concurrent with higher dietary intake and at times a decrease in corresponding foetal growth).
The consequences of the energetic burden of frequent reproductive cycling have been demonstrated among a relatively poor Guatemalan population (5), even when a convenient nutritional supplement was freely available between meals, twice daily over a seven year period, in addition to health services. The length of various components of the reproductive cycle were shown to affect the level of energetic burden and corresponding impact on indicators of maternal stores, intake and fetal growth. This was particularly apparent when examined across several reproductive cycles within the same women (6). In particular, those with lower reproductive stress and longer recuperative intervals showed lower levels of energetic stress. The Guatemalan data illustrate the complexity and variation common to reproductive cycling even within a relatively homogenous population. A recuperative interval in the reproductive cycle can be defined as the interval between complete weaning of the previous child and the beginning of the next pregnancy. During this interval, recovery from reproductive stress and from negative energy balance may be possible. A surprising finding within this Guatemalan population was that only about half experienced a recuperative interval, the other half of the sample of reproductively active women were pregnant while still breastfeeding their previous child. This condition of concurrent pregnancy and lactation (referred to as overlap) represents a high level of reproductive stress and eliminates the recuperative interval between reproductive cycles. Additionally, there was variation in the length of overlap interval as well as the length of the recuperative interval among these women. By characterizing reproductive stress based on short and long durations of each of these two types of intervals, it was possible to identify corresponding responses in maternal intake, fat stores, and foetal growth.
Although rarely examined, it appears that the phenomenon of overlap of lactation with subsequent pregnancy is much more common than previously believed and has been observed in regions such as Central Java, Senegal, Bangladesh, and the Philippines (7). Given the inherent complexities of the relationship between reproductive cycling and nutritional status, care should be taken before concluding that reproductive stress has an insignificant effect on womens nutritional status.
Areas for Research
Potential research areas include: (1) the development of quantified indicators of risk, for example consecutive conception interval of less than 30 months, first pregnancy under 18 years of age, and pregnancy after 40 years of age. These indicators of risk are only examples, research could be conducted to add validity and identify other indicators for specific population groups. For example other life style influences such as levels of undernutrition in a community, hardship of physical labour among women, and female age of marriage; and (2) improvement of the measurement of nutritional status of women, and improvement of the methodology used to characterize reproductive stress, given the complex variation created by reproductive cycling. Currently it is difficult to assess presence of maternal nutritional depletion. Assessment is problematic for two major reasons, maternal depiction typically is manifested by a general condition of undernutrition and is the consequence of several factors; and womens nutritional status is very complex and difficult to assess because of the reproductive cycle. This problem of assessment makes it very difficult to target potential beneficiaries to specific intervention programs.
Summary and Approaches for Alleviation of Maternal Nutritional Depletion
Too young, too old, too many and too close. This is how UNFPA(8) usefully summarizes the problem of frequent pregnancies and periods of lactation that contribute to nutritional depletion of the mother. The chronic undernutrition of maternal depletion not only results in poorer nutritional status for women and their offspring, but has been suggested to also accelerate aging and/or poorer health status for women. Although it is very difficult to attribute these effects directly to nutritional depletion, there is no doubt that the increased biological stress is accompanied by social/environmental stress for the mother due to the increase in family size. Specifically, the increase in family size usually further limits resources of time and money, potentially reducing the quality of care of the children while increasing the burdens on the mother and other adults of the household.
The approaches used to alleviate maternal nutritional depletion can be divided into direct and indirect groups. Direct approaches include: (1) increasing food intake with higher energetic density and quantity (ideally through increased frequency of small meals) of women prior to and during pregnancy, lactation and the following recuperative period; (2) reducing energy expenditure during pregnancy and postpartum; and (3) reducing the number of pregnancies, beginning reproduction later, ending reproduction earlier, and spacing conceptions to allow a minimum of 6 months recuperation following complete weaning of the previous child.
Indirect approaches include: (1) improving the status of women (education, later marriage, greater economic power, etc.); (2) improving resources available to the family (economic/shelter/health/education); and (3) reducing the burden of reproduction for women in a social context (reduction of work load, reduction of expected family size).
1. Jelliffe, D.B. & Maddocks, I. (1964). Notes on Ecologic Malnutrition in the New Guinea Highlands. Clin. Ped., 3(7): 432-438.
2. Winikoff, B. & Castle, M.A. (1987). The Maternal Depletion Syndrome: Clinical Diagnosis or Ecodemographic Condition? Paper presented for the International Conference on Better Health for Women and Children through Family Planning, held in Nairobi, Kenya, October 5-9, 1987.
3. Merchant, K. & Martorell, R. (1988). Frequent Reproductive Cycling: Does It Lead to Nutritional Depletion of Mothers? Prog Food Sci Nutr Sci, 12, 339-369.
4. Durnin, J.V.G.A. (1987) Energy Requirements of Pregnancy: An Integration of the Longitudinal Data from the Five-Country Study. Lancet, 2, 1131-1133.
5. Merchant, K.M., Martorell, R. & Haas, J.D. (1990). Maternal and Fetal Responses to the Stress of Lactation Concurrent with Pregnancy and Recuperative Intervals. Am J Clin Nut, 52, 280-288.
6. Merchant, K.M., Martorell, R. & Haas, J.D. (1990). Consequences for Maternal Nutrition of Reproductive Stress Across Consecutive Pregnancies. Am J Clin Nutri., 52, 612-620.
7. Martorell, R. & Merchant, K. (1992). Reproductive Stress and Womens Nutrition. Chapter 3 in: Nutrition and Population Links. ACC/SCN Symposium Report Nutrition Policy Discussion Paper No. 11.
8. UNFPA(1989) State of World Population 1989. Investing in Women: The Focus of the Nineties. United Nations Population Fund.